UNIVERSITY OF laiNOIS LIS^ARYi AT URBANA-CHA^/IPAIGiH AGRICULTURE NOTICE: Return or renew all Library Materials! The Minimum Fee for each Lost Book is $50.00. The person charging this material is responsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft mutilation, and underlining of books are reasons for discipli- nary action and may result in dismissal from the University. To renew call Telephone Center, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN Digitized by the Internet Archive in 2011 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/rowcropweedcontr8287univ 77 we-y UNIVERSITY Of ILLINOIS ^l /}' S^^ AGRICULTURE LIBRAm: nmiliniyo'll" c./ 1982 Row Crop Weed Control Guide " '="" university oi iliimMS TTii'c ,\Ac du me De to tio dit; an vo by I CO] cai -,»^ *l-«o ^«= -It ,1*-^ ^f ^^^ - ^ * ' HERTZBERG — NEW METHOD, INC. EAST VANDALIA ROAD, JACKSONVILLE, ILL. 62650 Q. iXjINY TITLE NO. ha 1-0 ACCOUNT NO. ( .■.■:.0's)-\'>. 'y. Store them in original containers, away from rized persons, particularly children. ;e manufacturers' formulations and labels are es changed and government regulations modi- 'ays refer to the most recent product label. ^ide has been developed to help you use herbi- efTectively and safely as possible. However, since J can remove all the risk involved, the University lonsibility for ty ye been used ')ns, or direc- ;ntal agency. LOT AND TICKET NO. CM 01 WA*. I >' ?--?V laJW « Lta;i- « \fi^£Xs ■■•s.- \..xji'iiROL ^ GUIDE ^ 43-24 :iV«2-B7« 632»95';»4^R77« 19B2^ CLOTH COLOR iini 01 Anv"^ HEIGHT 00 >d )er .ip. ani clo pla va] sev wil da^ crc no mc CHARGING INFORMATION SPECIAL WORK AND PREP. STUBBING HAND SEW THRU SEW THRU SEW ON TAPE HEIGHT // FRONT COVER NO TRIM PAGES LAMINATED EXTRA THICKNESS PICA 0~ HAND ADHESIVE LENGTHWISE FOREIGN TITLE LINES OF LETTERING MAP POCKET PAPER MAP POCKET CLOTH SPECIAL WORK REMOVE TATTLE TAPE II Bill HIFH 11 Hr >f ood cultural bicide appli- d control in- late fertiliza- te, use of the I for optimum ops compete -ing the first >th corn and J that period, ite well with and help the ver, if herbi- ol, then keep of the newer quate control ire' ivc m op n bee • Check label for proper method of container disposal. Triple rinse, puncture, and haul metal containers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or burn them in an approved manner. • Return unused herbicides to a safe storage place '^bie^otaryTioe atteTweed seeds have germinated r re most have emerged. Operate the rotary hoe at -■ miles per hour and weight it enough to stir the f a) kill the tiny weeds. Rotary hoeing also aids crop ce if the soil is crusted. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small Prepared by M. D. McGlamery, Professor of Weed Science, Ellery Knake, Professor of Weed Science, Mike Owen, Agronomist, Allan Beuerman, Assis- tant Agronomist, and F. W. Slife, Professor of Agronomy, all at the University of Illinois; with the assistance of George McKibben, Professor of Agron- omy, Dixon Springs Agricultural Center, George Kapusfa, Associate Professor of Plant and Soil Science, Southern Illinois University, Carbondale, and Gordon Roskamp, Associate Professor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist, USDA, and Professor of Weed Science, and E. W. Sfoller, Plant Physiologist, USDA, and Associate Professor of Agronomy, both at the University of Illinois. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbana-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. o o row ': : ?oro sis: rs >. ^ \ T o 5 /•. \ /4G.X c./ 1982 Row Crop Weed Control Guide UNIVERSITY OF ILLINOIS ^1 /)^ V^ AGRICULTURE LIBRARY ffM ubwy (If ^ JUL 15 1983 Univctrsity of llitnois w This guide is based on the results of research con- ducted by the University of Illinois Agricultural Experi- ment Station, other experiment stations, and the U.S. Department of Agriculture. Consideration has been given to the soils, crops, and weed problems of Illinois. Rainfall, soil type, method of application, and formula- tion influence herbicide effectiveness. Under certain con- t^ ditions some herbicides may damage crops to which they S are applied. In some cases, herbicide residues in the soil T: may damage crops grown later. i4<. When selecting a herbicide, consider both the risk in- ■■p volved in using the herbicide and the yield losses caused O by weeds. If cultivation and good cultural practices are fr controlling weeds, herbicides may be unnecessary. You ■<5 can reduce risks by taking these precautions: • Apply herbicides only to those crops for which use las been approved. jT: • Clean tanks thoroughly when changing from corn to * ' >ybeans, especially when using a postemergence her- i cide. • Use recommended rates. Applying too much herbi- de is costly and in addition may damage crops and luse illegal residues. Using too little herbicide can result 2 poor weed control. ^ • Apply herbicides only at times specified on the label. H bserve the recommended intervals between treatment r.j id pasturing or harvesting of crops. ^ • Wear goggles, rubber gloves, and other protective i^ othing as suggested by the label. ■-■• • Guard against drift injuiy to nearby susceptible _ ants, such as soybeans, grapes, and tomatoes. Mist or 4> -pors from 2,4-D, MCPA, and dicamba sprays may drift D veral hundred yards. Operate sprayers at low pressure '•'■ th tips that deliver large droplets. Spray only on calm ys or make sure air- is not moving toward susceptible >.:\ op plants and ornamentals. ^ • Apply herbicides only when all animals and persons t directly involved in the application have been re- )ved from the area. Avoid unnecessary exposure. • Check label for proper method of container disposal. Triple rinse, puncture, and haul metal containers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or burn them in an approved manner. • Return unused herbicides to a safe storage place promptly. Store them in original containers, away from unauthorized persons, particularly children. • Since manufacturers' formulations and labels are sometimes changed and government regulations modi- fied, always refer to the most recent product label. This guide has been developed to help you use herbi- cides as eflFectively and safely as possible. However, since no guide can remove all the risk involved, the University of Illinois and its employees assume no responsibility for results of using herbicides, even if they have been used according to the suggestions, recommendations, or direc- tions of the manufacturer or any governmental agency. Cultural and Mechanical Control Most weed control programs combine good cultural practices, mechanical weed control, and herbicide appli- cations. Good cultural practices to aid weed control in- clude preparation of a good seedbed, adequate fertiliza- tion, crop rotation, seeding on the proper date, use of the optimum row width, and seeding at the rate for optimum stands. Planting in relatively warm soils helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both corn and soybeans. If weed control is adequate during that period, com and soybeans will usually compete quite well with most of the weeds that begin growth later. Narrow rows will shade the centers faster and help the crop compete better with the weeds. However, if herbi- cides alone cannot give adequate weed control, then keep rows wide enough to allow cultivation. Some of the newer herbicides are improving the chances of adequate control without cultivation. Use the rotary hoe after weed seeds have germinated but before most have emerged. Operate the rotary hoe at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small Prepared by M. D. McGlamery, Professor of Weed Science, Ellery Knake, Professor of Weed Science, Mike Owen, Agronomist, Allan Beuerman, Assis- tant Agronomist, and F. W. Slife, Professor of Agronomy, all at the University of Illinois; with the assistance of George McKibben, Professor of Agron- omy, Dixon Springs Agricultural Center, George Kapusta, Associate Professor of Plant and Soil Science, Southern Illinois University, Carbondale, and Gordon Roskamp, Associate Professor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist, USDA, and Professor of Weed Science, and E. W. Stoller, Plant Physiologist, USDA, and Associate Professor of Agronomy, both at the University of Illinois. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbona-Chompaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. weeds, but be careful not to cover the crop. If a banded herbicide has given adequate weed control in the row, use shields to prevent soil movement into the row during the first cultivation. Cultivate shallow to prevent injury to crop roots. Avoid excessive ridging; it may hinder harvesting and encourage erosion. Herbicides can provide a convenient and economical means of early weed control by allowing delayed and faster cultivation. Furthermore, unless the soil is crusted, it is usually not necessary to cultivate at all when herbi- cides are controlling weeds adequately. Conservation Tillage and Weed Control Conservation tillage is a concept in which the soil is protected from erosion by leaving crop residue on the soil surface, or by making the soil surface rough while efficient crop production is maintained. The most common con- senation tillage systems are chisel, disk, and no-tillage. To gain the erosion-control benefit of conservation tillage, it is especially important that the soil surface be rough or at least partially covered with residue in the spring before and after com or soybeans are planted. The availability of a wide spectrum of eflfective her- bicides has made it possible to use conser\ation tillage for producing com and soybeans. Even with effective herbi- cides, however, the fear of poor weed control is probably the major deterrent to widespread adoption of conserva- tion tillage systems. A rough, cloddy soil surface or crop residue on the soil surface hinders chemical weed control in several ways. For example, clods that are not penetrated by the herbi- cide may later "melt down'' creating untreated weedy areas. In addition, crop residue on the soil surface inter- feres with herbicide performance and with thorough incorporation. Using implements for primary tillage other than the moldboard plow can also increase weed problems because they tend to leave a higher number of weed seeds on or near the soil surface. Because conser\'ation tillage systems disturb the soil and roots much less than conventional systems, perennial weeds are likely to become more of a problem. With conservation tillage, then, weed pressure is in- creased while overall herbicide performance is decreased. This situation presents a challenge to weed-control pro- grams. To insure the success of your program, exercise greater care in choosing herbicides and application rates and try to make more accurate and timely applications. By using preemergence herbicides, you can get better distribution with less secondan- tillage than with incorpo- rated treatments, although the success of preemergence herbicides depends more upon rainfall. In addition to preplant incorporated and preemergence herbicides, postemergence herbicides are also available. The effectiveness of postemergence herbicides in control- ling grass has varied more than that of soil-applied treat- ments. Thus, because preplant, preemergence and post- emergence herbicides have definite advantages as well as disadvantages, simply changing the time of application may not satisfactorily solve your \veed-control problem. To achieve satisfactory weed control with conservation tillage, you will need to apply herbicides at higher rates or use a sequence or combination of herbicides at higher rates. In any case, do not use a higher rate than indicated in the label instructions. Chemical Weed Control Plan your chemical weed-control program to fit your soil, crops, weed problems, and farming operations. Herbicide performance depends on the weather and on wise selection and application. Your decisions on herbi- cide use should be based on the nature and seriousness of your weed problems. Com or soybeans occasionally may be injured by some of the herbicides registered for use on them. However, the benefits from weed control are usually much greater than the adverse effects. Crop tolerance ratings for var- ious herbicides are given in the table on the last page of this article. Com or soybeans under stress from soil crust- ing, depth of planting, or adverse weather are more sub- ject to herbicide injury. Plants injured by a herbicide are likely to be more subject to disease. Apply the herbicide at the time specified on the label. Select and apply herbicides at the correct rate in order to reduce crop injury. The application rates for most herbi- cides vary with soil texture and organic matter. You must also consider the kinds of weeds likely to be present. The herbicide selectivity table at the end of this guide indicates the susceptibility of our most common weed species to herbicides. Crop planting intentions for the next season must also be considered. Where high rates of atrazine or simazine are used, you should not plant soybeans, small grains, alfalfa, or vegetables the following year. If you are con- sidering planting wheat after soybeans, be sure that the application of Treflan or similar herbicides for soybeans is uniform and sufficiently early to reduce the risk of injury to wheat or com following soybeans. Refer to the herbicide label for cropping sequence information. Names of Some Herbicides Trade Common (generic) AAtrex, Atrazine atrazine Amiben chloramben Banvel dicamba Basagran bentazon Basalin fluchloralin Bleep metolachlor + atrazine Bladex cyanazine Blazer acifluorfen Bronco alachlor + glyphosate Butoxone, Butyrac 2,4-DB Dowpon M dalapon Dual metolachlor Dyanap, Ancrack, Klean-Krop. . .naptalam plus dinoseb Eradicane, Eptam EPTC Evik - ametryn Furloe Chloro IPC chlorpropham Goal oxyfluorfen Hoelon dichlofop Laddok bentazon + atrazine Lasso alachlor Lorox linuron Milogard propazine Modown bifenox Paraquat paraquat Premerge 3 dinoseb Princep, Simazine simazine Prowl pendimethalin Ramrod, Bexton, Propachlor propachlor Roundup glyphosate Sencor, Lexone metribuzin (several) MCPA (several) 2,4-D Surflan oryzalin Sutan+ butylate Tolban profluralin Treflan trifluralin Vemam vemolate Some herbicides have different formulations and con- centrations under the same trade name. No endorsement of any trade name is implied, nor is discrimination against similar products intended. Herbicide Rates Herbicide rates vary according to the time of applica- tion, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence application than for pre- plant incorporated application. Postemergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary depending on the size and species of the weeds and on whether an adjuvant is specified. Rates for combinations are usually lower than for herbicides used alone. The rates for soil-applied herbicides usually vary de- pending on the texture of the soil and the amount of organic matter it contains. For instance, light-colored, medium-textured soils with little organic matter require relatively lower rates of most herbicides than do the dark- colored, fine-textured soils with medium to high organic matter. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemer- gence rather than soil-applied herbicide," depending on the herbicide and its adaptation and on crop tolerance. Reduced tillage systems usually require higher rates than conventional systems. Higher rates are especially necessary in the case of com stubble, since considerable crop residue remains on the soil surface. The rates given in this publication are, unless other- wise specified, broadcast rates for the amount of formu- lated product. If you plan to band or direct herbicides. adjust the amount p>er crop acre according to the per- centage of the area actually treated. Many herbicides have several formulations with different concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formulations. Herbicide Combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package mix," while others are tank mixed. Tank mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifiable concentrate (EC) formulations with wettable powder (WP) , water dispersible liquid (WDL) , water dispersible granule (WDG), or dry flowable (DF) formulations. These problems can sometimes be prevented by using proper mixing procedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides. If using liquid fertilizers, check compatibility in a small lot before mixing a tankful. The addition of compatibility agents may be necessary. Wettable powders, WDGs, DFs, or WDLs should be added to the tank before ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to prevent accumulation of material on the sides and the bottom of the tank. Some of the herbicide combinations that have been registered are listed below. The herbicide listed first is the one that carries label or supplemental instructions on mixing. The label of the other herbicide (s) may also have mixing instructions. Com Atrazine + Princep (PPI, Pre, NT/P, NT/R) ^ Atrazine + propachlor (Pre, early Post) Banvel + atrazine (Post) Banvel + Lasso (Pre, early Post) Banvel + 2,4-D (Post) Basagran + atrazine (Post) Bexton + Bladex (Pre) Bladex + atrazine (Pre, PPI, Post, NT/P) Bladex + atrazine + Lasso (PPI, Pre) Bladex + Paraquat (NT) Bladex + Sutan+ (PPI) Dual + AAtrex (PPI, Pre, eariy Post, NT/P, NT/R) Dual + Princep (PPI, Pre, NT/P, NT/R) Dual + atrazine + Princep (PPI, Pre, NT/P, NT/R) Dual + Banvel (Pre, early Post) Dual + Bladex (PPI, Pre) Eradicane + atrazine or Bladex (PPI) Eradicane + Bladex + atrazine (PPI) Lasso + atrazine (PPI, Pre, early Post, NT/P, NT/R) Lasso + Bladex (Pre, PPI, NT/R) Lasso + Princep (NT/R) Paraquat -f atrazine (NT) Prowl + atrazine (Pre, early Post) Prowl + Banvel (Pre) Prowl + Bladex (Pre, early Post) Sutan+ + atrazine (PPI) Sutan+ + atrazine + Bladex (PPI) Soybeans Alanap + 2.4-DB (Post) Amiben + Lasso (Pre) Amiben + Lorox (Pre) Amiben + Sencor (Pre) Amiben + Surflan (Pre) Amiben + Treflan (PPI) Amiben + Treflan + Sencor or Lexone f PPI ^ Basalin + Sencor or Lexone (PPI) Dual + Amiben (PPI, Pre) Dual + Dyanap (Pre, early Post) Dual + Lorox (Pre, NT/P, NT/R) Dual + Sencor or Lexone (PPI, Pre, NT/P, NT/R) Dyanap + Lasso (Pre, early Post) Furloe + Lasso (Pre) Furloe + Treflan orTolban (PPI) Furloe + Vernam (PPI) Goal + Treflan. Basalin, or Tolban (PPI) Goal + Lasso (Pre, NT/P) Lasso + Lorox (Pre, NT/P, NT/R) Lasso + Lexone or Sencor (Pre, PPI, NT/P), NT/R) Mo down + Lasso (PPI, Pre) ModowTi + Treflan (PPI) Paraquat + Lorox (NT) Paraquat + Sencor (NT) Prowl + Amiben (Pre) Prowl + Lorox (Pre) Prowl + Sencor or Lexone (PPI, Pre) Sencor + Amiben (Pre) Sencor or Lexone + Treflan (PPI) Surflan + Dyanap or Klean-Krop (Pre) Surflan + Lorox (Pre, NT/P) Surflan + Sencor or Lexone (Pre, NT/P) Tolban + Sencor or Lexone (PPI) Vernam + Treflan, Tolban, or Basalin (PPI) Vernam + Amiben (PPI) ' PPI = preplant incorporated, Pre = preemergence, Post = postemergence, NT = no-till, NT/P = no-till with Paraquat, NT/R = no-till with Roundup. The user can apply two treatments of the same herbi- cide (split application), or he can use two diflPerent ones, provided such uses are registered. Applying two herbi- cides at diff"erent times is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant application might be followed by a preemergence application, or a soil-applied treatment might be followed by a postemer- gence treatment. One herbicide may be broadcast while the other is banded or directed. Herbicide Incorporation Herbicides are incorporated into the soil to increase their eff"ectiveness. Some herbicides require incorporation to prevent their loss by volatility or photodecomposition. For herbicides that are not subject to \-olatilit\- or photo- decomposition, mechanical mixing into the soil is not imperative. Ho\\e\-er, incorporation ])ro\ides more con- sistent weed control than surface-applied herbicides that rely on rainfall. Optimum placement of a herbicide in the soil depends on the type of weeds to be controlled. Because annual weed seeds usually gemiinate from the top 1 or 2 inches of soil, most herbicides should be placed in that area for best results. Some herbicides are incorporated deeper (3 to 5 inches deep) in the soil to control large-seeded weeds or vegetative structures (tubers and rhizomes). They contain more stored food and can emerge from lower soil depths. The depth and thoroughness of incorporation depend upon the type of equipment, depth and speed of opera- tion, soil texture, and soil moisture. It is important to obtain uniform distribution, both horizontal and vertical, to prevent areas of high and low concentrations that may result in injun,-, residue, or poor control. Tandem disk harrows and field cultivators are the most commonly used tools for incorporation, although power-driven tillers, ground-driven seedbed conditioners, and com- bination tillage tools are also used. Tandem Disks Tandem disk harrows invert the soil profile in the same way as a moldboard plow, and usually place the herbicide deeper in the soil than most other tools used for incorporation. Travel speed and operating depth have the greatest effect on the vertical placement of her- bicides. At the gang angle used, travel speed should be sufficient to mo\e the soil at least the full distance of the blade spacing (usually speeds of 4 to 6 mph). Slower ground speeds can result in streaking of the herbicide. The highest concentration of herbicide is generally found at V2 to % of the depth of operation. Increasing the depth of operation increases the depth of incorporation. At a depth of 4 to 5 inches, the herbicide is distributed wdthin the upper 3 to 4 inches of soil, with the largest concentration in a layer 2V2 to 3 inches belo\v the soil surface. Incorporation efficiency decreases as disk-blade diam- eter increases (for example, from 18 to 22 inches), and as the spacing between the blades increases (for example, from 7 to 9 inches). Disks with blades larger than 22 inches and spaced \vider than 9 inches apart are con- sidered priman- tillage tools, and should not be used for incorporating herbicides. Disk blade shape also influences the ability of a disk to mix soil. Spherical blades (recommended for cutting residues and preparing seedbeds) give better herbicide mixing than conical blades. Conical blades, designed for penetration in heavy soil, are suitable for primary tillage but do not give unifomi soil mixing. One pass with a disk results in streaks of soil not mixed with herbicide. The addition of a coil-tine or spike-tooth drag harrow helps to level and mix the top layer of soil. Effectiveness diminishes as the disk is operated deeper than 3 to 5 inches because of limited soil penetration of the drag harrow. Two passes with a disk are recom- mended for thorough mixing, even when a harrow is used in combination with the disk. Preferably, the second pass should be made at an angle to the first pass. The timing of the second pass is not usually critical. If the herbicide is sufficiently covered on the first incorporation pass, the second pass can be delayed until the final seed- bed preparation immediately before planting. When properly operated, a small tandem disk is a useful implement for incorporating herbicides. Two passes in soil with good tilth (with the equipment operating 3 to 4 inches deep at 4 to 6 mph) usually results in adequate soil mixing for consistent weed control. Field Cultivators Field cultivators are used more than any other tillage tool for incorporating herbicides in Illinois. They are characterized by 2 or more rows of shanks (usually 3 rows) with an effective spacing of 6 to 9 inches (shanks spaced 18 to 27 inches apart on 3 tandem tool bars) . Travel speed, depth of operation, shank spacing, and the size of the points or sweeps determine the uniformity of incorporation. Shanks can be equipped with various points or sweeps, ranging from a 2-inch chisel point to 12-inch sweeps. Sweeps slice and lift the soil as the shanks are pulled through it. Sweep tilt, sweep size, and speed of operation all influence the amount of soil that is mixed. The effect of sweep size on incorporation is more im- portant under adverse conditions (too wet or too dry) than under optimal soil conditions. The lack of soil flow- in soils that are too wet or too dry can be partially com- pensated for by the greater surface area of a larger sweep. A field cultivator vvill distribute the herbicide from the soil surface to about Vi to % the depth of operation. As sweep size increases, the herbicide is moved slightly deeper into the soil ; under ideal soil conditions, however, the distribution is similar for 2-, 5-, 9- and 12-inch sweeps. Horizontal mixing of herbicides is erratic after one pass, even when followed by a coil-tine or spike-tooth drag harrow, but improves dramatically with a second pass made at an angle to the first pass. The recommended operating depth for the field culti- vator is 3 to 4 inches. It is usually best to operate a field cultivator only to the depth necessary to remove the tractor-tire depressions. The minimum ground speed for adequate incorporation varies with soil conditions and sweep size, but 6 mph is a practicable lower limit. The field cultivator must be operated in a level position. If the rear row of shanks is allowed to operate at a lower depth than the front gangs, untreated soil will be left on the surface, resulting in weed streaking. Two passes are recommended to obtain uniform weed control. The second pass should be made at an angle to the first. Herbicides on a large number of acres are incorporated with only one pass, using the field cultivator. Pattern streaking occurs under certain conditions, result- ing in erratic weed control. For this reason, two passes are recommended for uniform weed control. If herbi- cides are incorporated with only one pass, the use of wider sweeps on narrower spacings will increase the probability of obtaining uniform weed control. Soil texture and soil moisture greatly affect the degree of soil mixing. Soil moisture content is extremely critical to the uniformity of incorporation obtained with all till- age implements. Excessive moisture results in soil sticki- ness and greatly reduces soil flow, particularly in heavy- textured soils. Field cultivators depend upon soil flow from the sweeps for mixing, and when used in wet soils, much of the herbicide is left in streaks on the soil surface. In summary, there is not one incorporation technique that is best for all conditions. Several types of equipment are available that, if used properly, will provide adequate soil incorporation of herbicides under a variety of soil conditions. Herbicides for Corn All herbicides mentioned in this section are registered for use on field com and silage com. Herbicide sugges- tions for sweet com and p>opcom may be found in Cir- cular 907, 1982 Weed Management Guide for Commer- cial Vegetable Growers. Growers producing hybrid seed com should check vv'ith the contracting company or in- bred producer about tolerance of the parent lines. Preplant Incorporation Sutan+ and Eradicane should be incorporated im- mediately to minimize loss through vaporization. Incor- poration is optional for many other soil-applied com herbicides mentioned here. However, do not incorporate Banvel, Prowl, or propachlor. Preplant application should be done anytime during the 1 or 2 weeks prior to planting. Incorporation should distribute the herbi- cide evenly in the top 2 inches of soil. Incorporation of herbicides for which incorporation is optional may im- prove performance on some weed species, and if rainfall is limited it will improve performance on all susceptible weed species. However, do not apply herbicides too early or incorporate them too deep. Sutan+ (butylate) or Eradicane (EPTC) may be applied anytime during the 2 weeks prior to planting. They should be incorp>orated immediately. Both herbi- cides are formulated with a crop safening agent to de- crease the risk of com injury. However, injury can still occur when growing conditions are unfavorable or when certain hybrids are used. Sutan+ and Eradicane control the seedlings of annual grasses, shattercane, and johnsongrass. Eradicane will suppress wild proso mUlet. The suggested rate for these herbicides used alone or in combinations is 4% to 7V3 pints per acre. Use the higher amount on heavy infesta- tions of wild cane or yellow nutsedge or to suppress rhizome johnsongrass (see section on specific weed problems) . A lower rate may be used on sandy soils. You can control broadleaf weeds by tank mixing with atrazine or Bladex or by sequencing with an appropriate postemergence herbicide. The rate for combinations of Sutan+ or Eradicane with atrazine is 114 to 2 pounds of atrazine 80VV (2 to 3 pints of 4L), while the rate for Bladex is 1 Vi to 3% pounds of Bladex 80\V (2 to 6 pints 4L) . A combination of atrazine plus Bladex with Sutan+ or Eradicane is also registered in Illinois. Preplant or Preemergence Herbicides Incorporation of the following herbicides is optional depending upon the weeds to be controlled and the likeli- hood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 \\eeks prior to planting, or soon after planting. Preplant incorp>oration of these herbicides controls weeds more effectively if rain- fall is limited. Com tolerance of atrazine and simazine is good, but carnover to subsequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble, but just as persistent, as atrazine. Thus, Princep is usually preplant incorporated. Princep plus atrazine can be used in 1:1 or 2: 1 combinations; the total rate is the same as for atrazine used alone. The rate for atrazine used alone is 2V2 to 3% pounds of atrazine SOW, 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex 90\VDG. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank mix combinations to improve broadleaf weed control. The rate for atrazine in combi- nations is l'/2 to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to l.S pounds of AAtrex 90\VDG, These rates may not provide adequate control of cockle- bur, momingglory, and velvetleaf but can reduce the risk of carryover. You can minimize carryover injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil thoroughly before planting susceptible crops. The risk of carryover is greater the year after a cool, dry growing season and on soils with pH over 7.3. If you use atrazine at more than 3 pounds of active ingredient per acre or if you apply after June 10, plant only com or sorghum the next year. If you use atrazine in the spring and must replant, then plant only com or sorghum that year. Do not plant small grains, small seeded legumes, or vegetables in the fall or spring. Soybeans planted the year after an application of atra- zine can also be injured from carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not persist in the soil as long as atrazine, but atrazine does have the advantage of better com tolerance. Bladex controls fall panicum and giant foxtail, but not broadleaf weeds, better than atra- zine. Bladex can be combined with atrazine at 3:1, 2:1, or 1 : 1 ratios of Bladex to atrazine (see label for rates). The higher ratios will provide better grass control, while the 1 : 1 ratio will provide better broadleaf weed control. Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of com injury. Rates are IV2 to 5 pounds of Bladex SOW, 1.2 to 4 quarts Bladex 4L, or 8 to 27 pounds of Bladex 15G per acre. You can lessen the risk of com injury by using reduced rates of Bladex in combinations. Bladex can be tank mixed with Lasso, Dual, propa- chlor, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately prior to planting or after planting. Do not incorporate the Prowl or propachlor combinations. Lasso (alachlor) or Dual (metolachlor) can be ap- plied preplant incorporated or at the preemergence stage. Preplant incorporation will improve control of yellow nutsedge and can lessen dependence upon rainfall. Incorporation should distribute the herbicide evenly in the top 2 inches of soil. Lasso and Dual control annual grasses and help con- trol yellow nutsedge. You can improve broadleaf weed control by using atrazine or Bladex in preplant combina- tions or by using atrazine, Bladex, or Banvel in preemer- gence combinations. Lasso can be applied anytime during the week before planting com and incorporated evenly into the top 2 inches of soil, or it can be used immediately after plant- ing. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate for the soil if you plan to incorporate Lasso. Dual can be applied anytime during the 2 weeks prior to planting com and incorporated into the top 2 inches of soil, or it can be used immediately after planting. The rates are 1 V2 to 3 pints of Dual 8E per acre. Lasso or Dual plus atrazine can be applied preplant incorporated or after planting until com is 5 inches tall and grass weeds are no larger than the 2-leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is IV2 to 2V2 quarts of Lasso or VA to 2V2 pints of Dual 8E plus l'/2 to 2V2 pounds of atrazine BOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds or AAtrex 90^\ DG. Dual is also cleared in a combina- tion with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atrazine. Bleep contains 2V2 pounds of metolachlor (Dual) and 2 pounds of atrazine per gallon. The rate is 2 to 4 quarts per acre. Lasso and atrazine ^flowable) con- tains 2^/2 pounds of alachlor (Lasso) and 114 pounds of atrazine per gallon. The rate is 3'/2 to 4'/2 quarts per acre. Dual or Lasso plus Bladex can be applied prior to planting and incorporated, or they can be applied during the preemergence stage after planting. The rate is 2 to 2'/2 quarts of Lasso 4E or VA to 2'/2 pints of Dual 8E plus 1 to 3 pounds of Bladex SOW or 1.6 to 4.8 pints of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Lasso plus Bladex plus atrazine is also registered for use in Illinois. Preemergence Herbicides Banvel (dicamba) plus Lasso or Dual can be applied after planting until corn is 3 inches high, but before grasses reach the 2-leaf stage. The addition of Banvel improves control of broadleaf weeds without creating a risk of carryover injury. Banvel may injure com, especially if recommended rates are exceeded, applications are not accurate and uniform, or if com is planted too shallow (less than l'/2 inches). Do not use this treatment on coarse-textured soils or soils that are low in organic matter. The rate on soils with over 2V^2 percent organic matter is 1 pint of Banvel plus 2'/2 quarts of Lasso 4E, or 2 to 2V2 pints of Dual BE per acre. Ramrod, Bexton, or Propachlor (propachlor) can be applied alone or with atrazine after the corn is planted but before grasses reach the 2-leaf stage. Granular for- mulations should be applied before crop or weeds emerge. Propachlor performs well on soils with over 3 percent organic matter. Propachlor is irritating to the skin and eyes, so observe label precautions. Com tolerance to propachlor is good. It controls annual grasses and pigweed. The rate is 4 to 6 quarts of propachlor 4L or 20 to 30 pounds of propachlor 20G per acre. Propachlor can be mixed with atrazine or Bladex to improve broadleaf weed control. The rate is either 2'/2 to 4 quarts of propachlor 4L plus IV^ to 2 pounds of atrazine SOW (1.2 to 1.6 quarts of 4L) or l»/2 to 2'/4 pounds of Bladex SOW ( 1.2 to 1.8 quarts of 4L) per acre. Prowl (pendimethalin) is registered only for use on com after planting. Incorporation of Prowl may result in serious corn injury. Use only where it is possible to cover seed adequately with soil. Prowl can control annual grasses and pigweed and provides some control of smart- weed and velvetleaf. You can improve broadleaf weed control by combining Prowl with atrazine, Bladex, or Banvel. Prowl plus atrazine or Bladex may be applied in the early postemergence period before grasses are in the 2-leaf stage. These combinations may also help reduce the competition from wild proso millet. The rate for such combinations is 1 to l'/2 quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than 1 V2 percent organic matter. Postemergence Herbicides Lasso, Dual, propachlor, or Prowl plus atrazine as well as Lasso or Dual plus Banvel can be used on com be- tween the preemergence and very early postemergence stages (see preemergence section). To get satisfactory control apply before grasses reach the 2-leaf stage. Treflan is also labeled as a postemergence incorporated treatment in corn which is at least 8 inches in height. Treflan can be applied broadcast or directed and incorporated immediately with a cultivator. Banvel plus atrazine can be applied up to 3 weeks after planting but before annual grasses are l'/4 inches high. The rate is V2 pint of Banvel plus IV2 to 2 jxjunds of atrazine SOW or 1 to 1 .6 quarts of atrazine 4L. Atrazine can be applied before grass weeds are more than l'/2 inches high. Many annual broadleaf seedlings are more susceptible than grass weeds and may be treated until they are up to 4 inches tall. The addition of nonphytotoxic oils, oil-surfactant mixes, or surfactants has generally increased the effec- tiveness of postemergence atrazine. The nonphytotoxic oil is used at 1 gallon per acre. Crop-oil concentrates (SO percent oil and 20 percent surfactant) are used at the rate of 1 quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or about 1 pint per acre. Results with the oils and oil-surfactant mixes have generally been better than those with the surfactants. Applications of atrazine and oil sometimes damage corn that has been under stress from prolonged cold, wet weather, or other factors. Do not use more than 2^/2 pounds of atrazine SOW or 2 quarts of atrazine 4L per acre if you mix with oil or oil concentrate. Do not add 2,4-D to the atrazine-oil treatment or severe injury may result. Mix the atrazine with water first and add the oil last. If atrazine is applied after June 10, do not plant any crop except com or sorghum the next year. Bladex (cyanazine) can be applied through the 4-leaf stage of com growth but before weeds exceed IV2 inches in height. The rate is l'/2 to 2V2 pounds of Bladex SOW per acre. (Do not use Bladex 4L.) A mixture of Bladex + atrazine is also registered for postemergence use. In- jury to com may occur under cold, adverse growing con- ditions. The injury may only be temporary yellowing, but can be more severe. Certain agricultural surfactants or vegetable oils may be added to Bladex, but do not use petroleum crop oils or apply with liquid fertilizers for postemergence application. Banvel (dicamba) can be applied either early or late in the postemergence stage. If you apply it early, use it at a rate of V2 to 1 pint per acre anytime after planting until com is 5 inches high. The best time to apply is at the first flush of broadleaf weeds. Banvel should be used in a sequential treatment with a grass herbicide such as Lasso, Dual, or Sutan + . Such timing allows for better crop tolerance than the preemergence treatments with Banvel, permits a higher rate than the later postemer- gence treatment, and diminishes the likelihood of signifi- cant soybean injury. Banvel should be applied before soybeans in the area are 10 inches high. Soybean yields are seldom reduced when slight injury occurs early. However, yields can be reduced if severe injury occurs when soybeans are bloom- ing or during pod fill. Banvel also can injure other sus- ceptible plants, such as vegetables and ornamentals. Use extreme caution to avoid injury to desirable plants from either contaminated sprayers or drift of Banvel from treated areas. Banvel may be applied until com is 3 feet high or until 15 days before tasseling. When spraying near soy- beans, do not spray com after it is 2 feet high. If com is more than 8 inches high, drop nozzles give better weed coverage and reduce drift. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com. The broadcast rate is V2 pint per acre. Do not use Banvel on sweet com, popcorn, or seed com. Do not graze or harvest com for dairy feed before the ensilage (milk) stage. A mixture of ¥2 pint of Banvel plus Vi pint of 2,4-D amine (4 pounds per gallon) per acre may present less risk of com injury than 2,4-D alone. Use drop nozzles on com more than 8 inches high when using the Banvel- plus-2,4-D mixture. 2,4-D is an economical and effective treatment for controlling many broadleaf weeds in com. Use drop nozzles if com is more than 8 inches high to decrease the possibility of injury. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com. Do not apply 2,4-D to com from tasseling to dough stage. After the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-D's by air or high clearance equipment to control late-germinating broadleaf weeds that may interfere with harvest, or to suppress certain perennial weeds. The suggested broadcast rate of acid equivalent per acre is Ve to '4 pound of ester formulations or V2 pound of amine. This would be Vs to V2 pint of ester or 1 pint of amine for formulations with 4 pounds of 2,4-D acid equivalent per gallon. The ester forms of 2,4-D can vaporize and injure near- by susceptible plants. This vapor movement is more likely with high-volatile than with low-volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Com is often brittle for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other symptoms of 2,4-D in- jury are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. High temperature and high humidity will increase the potential for 2,4-D injury, especially if com is growing rapidly. If it is necessary to spray under these conditions, it may be v^se to reduce the rate by about 25 percent. Com hybrids differ in their sensitivity, and the proba- bility of injury increases when com is under stress. Basagran (bentazon) is registered for postemergence use in com in a manner similar to that for soybeans (see soybean section) . Since com is quite tolerant of Basagran, the addition of a crop-oil concentrate is considered rela- tively safe. Basagran is also cleared in combination with atrazine plus oil at the rate of 1 to IV2 pints of Basagran plus atrazme at 0.6 to 0.9 pound of 80W, 0.6 to 0.8 pound of 90WDG, or 1 to V/2 pints of 4L per acre. Oil concentrate is added at 1 quart per acre for control of annual broadleaf weeds only. The combination is more economical than Basagran alone and will reduce the carryover potential from atrazine alone. Laddok is a mixture of 1% pounds bentazon (Basa- gran) plus 1% pounds of atrazine per gallon. It can be used to control broadleaf weeds in com with 1 to 5 leaves. The rate is 2.4 to 3.6 pints Laddok plus one quart of crop oil concentrate per acre. Directed Posfemergence Herbicides Directed sprays are sometimes needed for emergency situations, especially when grass weeds become too tall for control with cultivation. However, weeds are often too large for directed sprays to be effective. Directed sprays cannot be used on small com because a height difference between com and weeds is needed to keep the spray off the com. Com leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox (Hnuron) may be applied as a directed spray after com is at least 15 inches high (free standing) but before weeds are 8 inches tall (preferably not more than 5 inches) . Lorox controls grass and broadleaf weeds. The broadcast rate is IVi to 3 pounds of Lorox 50W per acre, depending on weed size and soil type. Add Sur- factant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the com as much as possible. Consider this an emergency treatment. Evik SOW (ametryn) is registered for directed use when com is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 2*/2 pounds Evik 80 W p>er acre (broadcast) plus 2 quarts of surfactant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Herbicides for Soybeans Consider the kinds of weeds expected when you select a herbicide program for soybeans, especially when grow- ing soybeans in narrow rows. The herbicide selectivity table (see last page) lists herbicides and their relative weed control ratings for various weeds. Soybeans may be injured by some herbicides. However, they usually outgrow early injury with little or no effect on yield if stands have not been significantly reduced. Significant yield decreases can result when injury occurs during the bloom to pod fill stages. Excessively shallow planting may increase the risk of injury from some herbi- cides. Accurate rate selection for soil type is especially essential for Lorox, Lexone, and Sencor. Do not apply Lorox, Lexone, Sencor, Modown, or Goal after soybeans have begun to emerge. Follow label instructions as to rates, timing, incorporation, and restrictions. Preplant Herbicides Incorporation is required for Basalin, Tolban, Treflan, and Vernam. Incorporation is optional for Amiben, Dual, Lasso, Modown, and Prowl when used alone and in some combinations. Dyanap, Lorox, and Surflan should not be incorporated. Incorporation can improve performance if rainfall is limited and may increase the eflfectiveness of Dual or Lasso in controlling nutsedge. Incorporation should distribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early application of the herbicide can cause significant reductions in weed control. Dinitroaniline herbicides registered for weed control in soybeans are Basalin, Tolban, Treflan, Prowl, and Surflan. Basalin, Treflan, and Tolban should be incorpo- rated because of their low solubility and because of sur- face loss through vaporization and photodecomposition. Incorporation is optional with Prowl, but variable weed control and soybean injury may result from preemergence applications. Do not incorporate Surflan (see preemer- gence section) . How early you apply a dinitroaniline herbicide de- pends on the particular herbicide and on whether it is applied alone or in combinations. Combination treat- ments usually call for application within 7 to 14 days of planting. Too early an application followed by delayed planting may result in poor weed control. How long you delay incorporation depends on the herbicide, but de- laying incorporation may lead to loss of herbicide from erosion, photolysis, or vaporization. Incorporation should distribute the herbicide evenly in the top 2 to 3 inches of soil (see label for implement settings) . A deeper incorpo- ration may improve shattercane and johnsongrass seedling control. Basalin, Tolban, Prowl, and Treflan may be used for rhizome johnsongrass suppression (see section on specific weed problems). The dinitroaniline herbicides control annual grasses, pigweed, and lambsquarters and may provide some con- trol of smartweed and annual morningglory. Prowl and Surflan may also partially control velvetleaf. However, acceptable control of most other broadleaf weeds re- quires combinations or sequential treatments with other herbicides. Sencor or Lexone can be tank mixed with any of the dinitroaniline herbicides. The dinitroaniline herbicides provide similar weed con- trol, soybean tolerance, and persistence when recom- mended rates are used. Soybeans are sometimes injured by dinitroaniline herbicides. Plants that have been in- jured by incorporated treatments are stunted and de- velop swollen hypocotyls and shortened lateral roots. Such injuries are not usually serious. Plants injured by preemergence applications develop stem callouses at the soil surface, which can cause lodging and yield loss. Crops of com, sorghum, or small grains may be injured if they are grown subsequent to a soybean crop that has been treated with a dinitroaniline herbicide. The symp- toms are poor germination and stunted, purple plants with poor root systems. To avoid carryover use no more than the recommended rates. Also, be sure that applica- tion and incorporation are uniform. The likelihood of carryover increases with double cropping or late applica- tion and after a cool, dry season. Disking or chisel plow- ing provides for minimal dilution of herbicide residues. Treflan (trifluralin) can be applied alone anytime in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks prior to planting, while combinations with Amiben, Furloe, or Modown should be applied within a few days prior to planting. Incorpo- rate as soon as possible, but do not delay incorporation more than 24 hours (8 hours if soil is warm and moist). The rate is 1 to 2 pints of Treflan 4E or 10 to 20 pounds of Treflan 5G per acre. Tolban (profluraHn) should be applied within a few days prior to planting soybeans. Incorporate within 4 hours of application. The rate is 1 to 3 pints of Tolban 4E per acre. Combinations may allow lesser amounts, al- though to control shattercane you may need to use the higher rate. Tolban can be tank mixed with Sencor, Lexone, or Furloe to improve broadleaf control. Tolban will no longer be manufactured, but current supplies may be used. Basalin (fluchloralin) can be applied anytime during the 8 weeks (alone) or 1 to 2 weeks (with Sencor or Lexone) prior to planting. Incorporate within 8 hours of application. The rate is 1 to 3 pints Basalin 4E per acre. Basalin can be combined with Sencor vr Lexone to im- prove broadleaf weed control. Prowl (pendimethalin) can be applied within 60 days (alone) or 7 days (with Sencor or Lexone) prior to planting soybeans or applied after planting (see pre- emergence) . Preplant treatments should be incorporated within 7 days of application. Mechanical incorporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, although rates for combinations with Sencor or Lexone are lower than when the herbicide is used alone. Sencor or Lexone (metribuzin) plus Basalin, Prowl, Treflan, or Tolban can be tank mixed and applied within 7 to 14 days of planting. Incorporate evenly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is V2 to 1 pound of SOW, V2 to 1 pint of 4L, or Vs to Vs pound of 75DF. Use the normal rate, or slightly less, of the dinitroaniline herbicide (see labels). Vernam (vernolate) controls annual grasses and pig- weed. It sometimes provides fair control of annual morn- ingglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vemam can be applied wdthin 10 days prior to planting and should be incorpo- rated immediately. The broadcast rate is 2'/3 to 3'/2 pints of Vemam 7E or 20 to 30 pounds of Vemam lOG per acre. Vemam plus Treflan is labeled at the rate of 1 pint of Treflan plus 2V3 to 3 pints of Vemam 7E per acre. The combination will reduce the risk of soybean injury, but it may also decrease control of velvetleaf and yellow nutsedge. Other labeled combinations include Vernam plus Amiben, Basalin, or Tolban. Preplant or Preemergence Herbicides Lasso (alachlor) or Dual (metolachlor) can be ap- plied to soybeans preplant incorporated or during the preemergence stage. If applied prior to planting, apply Dual anytime within the 2 weeks prior to planting and Lasso within 1 week of planting. If rainfall is limited, incorporation can improve performance and increase yellow nutsedge control. Soybeans are quite tolerant of Lasso or Dual. The first to second trifoliate leaves often appear crinkled with a drawstring effect on the middle leaflet, but these symptoms should not cause concern. Lasso or Dual controls annual grasses plus pigweed and can help control nutsedge (see section on specific weed problems) . These herbicides can be combined with Lexone, Sencor, or Amiben (incorporated or preemer- gence) and with Lorox or Dyanap (preemergence only) to improve broadleaf weed control. Lasso can also be combined with Modown or Goal. The rate for Lasso is 2 to 4 quarts Lasso 4E or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is VA to 3 pints per acre. Use the higher amount for the soil when incorporating. The rate for combinations is about 75 percent of that for the herbicide used alone (see labels). Amiben (chloramben) can be applied alone or with Treflan or Dual within a few days prior to planting. It can also be tank mixed with Treflan plus Sencor or Lexone as a preplant incorporated treatment. Amiben can be applied preemergence alone or with Dual, Lasso, Surflan, or Prowl to improve grass control, or with Lorox, Lexone, or Sencor. If it does not rain within 3 to 5 days of preemergence application, you should rotary hoe. Amiben can control many weeds in soybeans, but do not expect control of cocklebur or annual momingglory. Control of velvetleaf and jimsonweed is often erratic, especially at lower rates or with low rainfall. Amiben occasionally injures soybeans, but damage is not usually severe. Injured plants may be stunted and have ab- normal, shortened roots. The rate is 4 to 6 quarts Amiben 2S or 20 to 30 pounds of Amiben lOG per acre. The rate in most combinations is 3 to 4 quarts Amiben 2S per acre. Amiben is best suited to soils with over 2.5 percent organic matter. Sencor or Lexone (metribuzln) can be applied any- time during the 1 to 2 weeks prior to planting and in- corporated with Basalin, Dual, Lasso, Prowl, Treflan, or Tolban. Incorporation should distribute the herbicide evenly in the top 2 inches of soil. It can be applied pre- emergence by itself or with Amiben, Dual, Lasso, Prowl, or Surflan. Sencor or Lexone can control many annual broadleaf weeds except annual momingglory. Control of giant rag- weed, jimsonweed, and cocklebur is often marginal at the reduced rates necessary to minimize soybean injury. One symptom of soybean injury is yellowing (chlorosis) of the lower leaves at about the first trifoliate stage or later; it may be followed by browning of leaves and death of plants depending upon the severity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with pH over 7.5. Accurate, uni- form application and incorporation are essential. Adjust rates accurately according to soil conditions. Do not apply to very sandy soil. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is V2 to 1 pound of SOW, V2 to 1 pint of 4L, or V3 to % pound of 75DF. You can use the higher amount when you apply this treatment during the preemergence stage, either alone or sequentially after application of a preplant herbicide. The higher amounts can improve broadleaf weed control, particularly of cocklebur, but they also increase the risk of soybean injury. Modown (Bifenox) or Goal (oxyfluorfen) primarily controls broadleaf weeds such as pigweed, lambsquarters, and smartweed with some control of jimsonweed and velvetleaf. Combinations with grass herbicides will im- prove grass control. Goal or Alodown can be tank-mixed for preplant in- corporation with Treflan or for preemergence treatment with Lasso. For preplant incorporation, Modown can also be mixed with Lasso, and Goal can be mixed with Basa- lin or Tolban. Preplant incorporation treatments should be applied within 2 or 3 days of planting. Incorporation should evenly place the herbicides into the top 1 to 2 inches of soil. Preemergence treatments should be applied within a few days after planting. Do not apply Goal or Modown after the soybeans begin to emerge. Soybeans may show stunting from Modo\vn or Goal, especially from preemergence use. This injury may be apparent if splashing rains occur shortly after emergence, or when cold, wet soil conditions occur during the early growth stages. Injury symptoms are leaf cupping and crinkling on the first few leaves. Soybeans usually recover sufficiently from this early injury to prevent yields from being affected. Modown rates in combinations with herbicides for grass control are 2V2 to 4 pints 4F or IV2 to 2'/2 pounds SOW per acre. The rate of Goal 2E is 1 to V/2 pints per acre for preemergence use with Lasso, or W2 to 2 pints per acre for incorporation with Treflan, Basalin, or Tolban. Goal is also registered with Paraquat and Lasso 10 for no-till soybeans, and this use will probably be the primary one for Goal in 1982. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan, Tolban, or Vemam; or it can be applied preemergence by itself or with Lasso to im- prove smartweed control. Preplant application should be done within a few days of planting soybeans, and in- corporation should distribute the herbicide evenly in the top 1 to 2 inches of soil. The rate in sequential or tank mix combinations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preemergence Herbicides Lorox (Hnuron) is best suited to silt loam soils that contain 1 to 3 percent organic matter. Do not apply to very sandy soils. Lorox controls broadleaf weeds better than grass weeds. It does not control annual morning- glory, and control of cocklebur and jimsonweed is vari- able. Accurate and uniform application, and proper rate selection are necessary to minimize the risk of crop injury. Tank-mix combinations allow the use of a reduced rate of Lorox to decrease the risk of soybean injury, but may also decrease the degree of weed control. Lorox is registered in tank-mix combinations with Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of Lorox in these combinations is 1 to VA pounds of Lorox SOW or V2 to % pints of Lorox 4L on silt loam soils with less than 3 percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if there is adequate rainfall. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after applica- tion. Do not use on soils of more than 5 percent organic matter. The rate is 1 to 2 pounds per acre of Surflan 75W {Vi to V/2 quarts 4L) used alone or % to 1% pounds of Surflan 75W in combinations. Surflan can be tank mixed with Amiben, Lorox, Lexone, Sencor, Dyanap, or Klean-Krop to improve broadleaf weed control. Prowl can be applied preemergence in combination with Amiben, Lexone, Lorox, or Sencor. When applied to the soil surface. Prowl may cause stem callousing, which can lead to soybean lodging and yield reduction. (See preplant section for more information.) Dyanap (dinoseb plus naptalam) can be applied to soybeans from the time they are planted until the uni- foliate leaves of the seedling unfold and expose the growing point. A tank mix of Dyanap plus Lasso, Dual, or Surflan is registered to improve grass control. Ancrack and Klean-Krop are other trade names for dinoseb plus naptalam. However, they are not registered in combina- tion with Lasso or for postemergence application. They are registered for preemergence use with Surflan. Postemergence Herbicides In the past, most farmers have placed primary empha- sis on controlling weeds early with preplant or preemer- gence applications, and have considered postemergence applications as a backup measure when control from earlidr treatments was not adequate. Research suggests, however, that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after planting. The trend toward reduced tillage could encourage greater emphasis on postemergence treatments. Postemergence herbicides are most effective when their use is part of a planned program, and when they are applied while the weeds are young and tender. They should not be considered simply an emergency treatment. It is especially important to use timely treatments when using postemergence herbicides in narrow-row soybeans. Postemergence herbicides are often the best choice for controlling certain problem weeds such as cocklebur, annual momingglory, and volunteer com. Most of the currently available postemergence herbi- cides for soybeans do not give adequate control of annual grasses such as giant foxtail, and should be used in sequence with preplant incorporated or preemergence herbicides that control annual grasses. Soybeans may be injured by some postemergence herbi- cides. If there is an adequate height difference between soybeans and weeds, the amount of soybean injury can be decreased by directing some herbicides toward the weeds and minimizing contact with the soybeans. Premerge (dinoseb) can be applied in the early post- emergence period when soybeans are still in the seedling stage before first leaves open to expose the terminal bud. To control emerged weeds such as cocklebur, moming- glory, and jimsonweed, use 3 quarts per acre if the ex- pected air temperature is below 75° F., and 2 quarts if it is from 75 to 95° F. Do not apply above 95° F. For residual control, Premerge can be tank-mixed with Amiben or Lasso. Caution: Premerge is very toxic to man and animals. Amiben (chloramben) can be applied at 5 to 6 quarts per acre when soybeans are in the cracking to second trifoliate stage of growth. This treatment may control or suppress velvetleaf or smartweed that is less than 4 inches tall. Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf. It is weak on pigweed, lambsquarters, and annual morning- glory. It can provide some control of yellow nutsedge and Canada thistle but not of annual grasses. The suggested rate for Basagran is M to 1 quart per acre, depending on weed size and species. Application should be done when weeds are small (2-3 inches) and actively growing. These conditions usually exist when the soybeans are in the unifoliate to second trifoliate stage. Spraying during warm sunny weather can also improve performance. Use a minimum of 20 gallons of water per acre in order to get complete weed coverage. Adding a surfactant or crop-oil concentrate to Basagran may in- crease performance, particularly on yellow nutsedge, 11 velvetleaf, and momingglory, but may cause some soy- bean injury. Blazer (acifluorfen) is a postemergence herbicide used to control broadleaf weeds in soybeans. The rate is 2 pints of Blazer 2S when broadleaf weeds are at the 2- to 4-leaf stage and growing actively. Blazer controls annual momingglory, black nightshade, and pigweed better than Basagran, but Basagran is better on cocklebur and velvet- leaf. Under ideal conditions, Blazer may also help con- trol very small, escaped annual grasses. Blazer is primarily a contact herbicide. Suggested spray volumes are 20 to 40 gallons per acre with a spray pressure of 40 pounds per square inch. Surfactants or crop oils are not recom- mended with Blazer. Do not spray if rain is anticipated within 6 hours. Dyanap (dinoseb plus naptalam) can be applied to soy- beans after the second trifoliate leaf opens until beans become 20 inches tall. Two to 3 quarts per acre is recom- mended for control of cocklebur, jimsonweed, smartweed, and annual momingglory less than 3 inches tall. Four quarts per acre may control cocklebur and jimsonweed taller than 3 inches. A split application of 2 quarts at the second trifoliate stage followed by 2 quarts 10 to 14 days later is recommended for severe weed infestations. Best results are obtained by using high pressure (40 to 60 pounds per square inch) and 8 to 10 gallons of water per acre. Although leaf bum can occur, the crop usually recovers within 2 to 3 weeks with little or no yield loss. Do not apply Dyanap to wet soybean foliage. Hoelon (dichlofop) may control many annual grass weeds and volunteer corn. Annual grass weeds should be in the 1- to 4-leaf stage of growth, volunteer com should be less than 10 inches high, and soybeans should be at the fifth trifoliate stage or less. The rate is 2 to 3V3 pints of Hoelon 3E per acre in at least 20 gallons of water. Because thorough coverage of the foliage is essential, a minimum pressure of 20 pounds per square inch is recommended. Do not use Hoelon in a tank mix- ture with other postemergence herbicides. Hoelon is a restricted-use herbicide. Vistar (mefluidide) may be used for postemergence control of johnsongrass in soybeans south of Highway 1-70 in Illinois. Vistar may also suppress some other grasses such as volunteer corn and shattercane. Vistar 2S is used at the rate of 1 pint per acre after the second tri- foliate stage of soybeans, and when johnsongrass is less than 15 inches tall. If new growth or regrowth of johnsongrass occurs, a second application may be neces- sary 3 to 4 weeks after the first application, but no later than 60 days prior to harv^est. A nonionic surfactant such as Citowett or Surfactant WK should be used at the rate of 1 to 2 pints per 100 gallons of spray solution. Johnsongrass is not immediately killed by Vistar, and usually about 10 days will elapse before the leaves turn brown. Maximum results will be seen in about 3 weeks. Soybeans may also show some injury from Vistar, as indi- cated by leaf crinkling or slight growth suppression. Directed Postemergence Herbicides Roundup (glyphosate) can be applied through several types of selective applicators — recirculating sprayers, wipers, or rope wicks. This application is particularly useful for control of volunteer com, shattercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be a minimum of 6 inches above the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soy- beans. For calibration of equipment, refer to the Round- up label. If you use a recirculating sprayer, apply 4 quarts of Roundup in 20 gallons of water to suppress perennial broadleaf weeds. To control perennial grass and annual weeds, use 2 to 3 quarts of Roundup in 20 gallons of water. For wiper or roller type applicators, mix 1 to 2 gallons of Roundup in 20 gallons of water. Use the higher amount for heavy weed infestations, perennial weeds, and annual broadleaves. For rope wick applica- tors, mix 1 gallon of Roundup in 2 gallons of water. Alanap-L (naptalam) plus 2,4-DB is labeled for use 7 to 10 days before soybeans bloom through mid-bloom. Rates are 2 to 3 quarts of Alanap-L plus 3 to 4 ounces of Butoxone SB or Butyrac 200 per acre. Ground applica- tion should be at 10 to 20 gallons of spray volume per acre, using hollow cone nozzles positioned 18 to 24 inches above the soybeans or weeds. Maintain spray pressure at 40 to 50 psi. Butoxone SB and Butyrac 200 (2,4-DB) are used for directed postemergence control of cocklebur in soybeans. 2,4-DB also may give some control of annual moming- glory and giant ragweed. Consider 2,4-DB for emergency control of cocklebur when potential benefit from weed control is more significant than risk of soybean injury. Injury symptoms include leaf wilting, stem curvature, and cracking of stems. 2,4-DB alone or in combination with Lorox can be directed when soybeans are at least 8 inches high and cockleburs are less than 4 inches high. Do not spray on more than the lower third of the soy- bean plant. Lorox plus 2,4-DB, or Paraquat alone are also cleared for directed postemergence treatment in soy- beans. Soybeans must be at least 8 inches tall and weeds not over 2 inches tall. Nozzles must be adjusted accur- ately to spray only the lower one-third of the soybean plant or serious soybean injury can occur. Read the labels for the correct rates and precautions. Goal (oxyfluorfen) may be used as a directed post- emergence treatment for control of cocklebur, prickly sida, and annual momingglorv'. Soybeans should be at least 8 inches high and weeds not over 4 inches high. Adjust nozzles to minimize spray contact with the soy- beans. Paraquat Harvest Aid Paraquat is registered for drying weeds in soybeans just before harvest. For indeterminate varieties (most Illinois 12 varieties) , apply when 65 percent of the seed pods have reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when beans are fully developed, at least one-half of the leaves have dropped, and remaining leaves are turning yellow. The rate is '/a to 1 pint of Paraquat per acre. The higher rate is for cocklebur. The total spray volume per acre is 2 to 5 gallons per acre for aerial application or 20 to 40 gallons for ground application. Add 1 quart of Ortho X-77 Spreader per 100 gallons of spray. Do not pasture livestock within 15 days of treatment, and remove livestock from treated fields at lezist 30 days before slaughter. No-Till and Double-Crop Com and soybeans are sometimes produced without seedbed preparation, either in last year's crop residue (no- till) or as a second crop after small grain harvest or forage removal (double-crop). The no- till concept of planting has greatly improved the probability of success of double-cropping by conserving soil, soil moisture, and time. No-till herbicides must control both vegetation existing at planting and seedling weeds that germinate after planting. Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop, or weeds that emerge in the previous years' crop stubble before planting. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor. Labeled applications of 2,4-D, Roundup, or Banvel can improve control of broad leaf perennials when used in registered crops, such as com or sorghum. Several precautions should be observed in no-till crop- ping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact from herbicide sprays. (Several herbicide labels give planting depths necessary to avoid possible injury.) Pre- emergence applications of the herbicide treatment may give better weed control than preplant applications since the planting process may expose untreated soil contain- ing viable weed seed. The total reliance on chemical weed control and large amounts of crop residue present under no-till cropping systems may require that the higher labeled herbicide rates be used to obtain accept- able weed control. Paraquat ( 1 or 2 pints per acre) plus a nonionic sur- factant, such as Ortho X-77, at V2 pint per 100 gallons of diluted spray is generally used to "knock down" exist- ing foliage before crop emergence. Smartweed, giant rag- weed, and fall panicum may not be controlled if they are over 10 to 12 inches high and if no rain occurs to "acti- vate" the residual herbicides. Since Paraquat provides only contact action, a minimum of 40 gallons or more of spray per acre is suggested to insure adequate coverage of the foliage. Paraquat is a restricted-use pesticide. Roundup (3 pints per acre) should be considered as an alternative treatment for control of the foliage prior to crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can translocate to the roots to give better con- trol of perennials. Use 20 to 40 gallons of spray volume per acre. Bronco is a formulated mixture of glyphosate (Round- up) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Do not apply in liquid fertilizers. No-iill Corn Herbicides registered with Paraquat plus atrazine are Dual, Lasso, Princep, and Bladex. Dual plus Princep, atrazine plus Princep, and Bicep are also registered with Paraquat. These combinations give better control of annual grasses than atrazine or Bladex plus Paraquat. Herbicides registered with Roundup plus atrazine or Princep are Dual and Lasso. Roundup is also registered with atrazine plus Princep, atrazine plus Princep plus Dual, Lasso plus Bladex, and Bicep for use in no-till com. Bronco is registered for use with atrazine, Bladex, or Princep. No-till or Double Crop Soybeans Preemergence herbicides registered in soybeans as tank mixes with Paraquat (1 to 2 pints per acre) plus Ortho X-77 surfactant are Lorox, Sencor, or Lexone alone or in combination with Lasso, Dual, or Surflan. Goal plus Lasso is also cleared with Paraquat. Registered tank mixes with Roundup are Lasso or Dual in combination with Lorox, Sencor, or Lexone. Bronco is registered with Lexone, Lorox, or Sencor. Herbicides for Sorghum Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Ap- plication may be made preplant, preemergence, or post- emergence. Plant seed at least 1 inch deep. Do not use preplant or preemergence on soils with less than 1 per- cent organic matter. Incorporated treatments may show injury if rainfall occurs prior to or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemer- gence is 2 to 3 pounds of atrazine SOW per acre. The postemergence rate is 2'/2 to 3% pounds SOW per acre. Rotational crop recommendations and weed control are the same as for atrazine used in com. Failure to control fall panicum has been a major problem. Ramrod, Bexton, or Propachlor (propachlor) may be used alone or in combination with atrazine, Milogard, Bladex, or Modown for sorghum. Propachlor will im- prove grass control, but rates must not be skimpy, espe- cially on soils relatively low in organic matter. For spe- cific rates, consult the product label. Dual (metolachlor) or Dual plus atrazine (or Bicep) 13 can be used on sorghum seed that has had the Concep- seed treatment. These herbicides will improve grass con- trol more than atrazine applied alone. Milogard (propazine) has better sorghum tolerance than atrazine, but grass control is not as good. Only corn or sorghum may be planted in rotation within 12 months after treatment. 2,4-D may be applied postemergence for broadleaf control in 4- to 12-inch tall sorghum. Use drop nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in com (see page 8) . Banvel can be applied postemergence until sorghum is 15 inches tall or 25 days after emergence. The rate is y^ pint per acre. Do not graze or feed treated forage or silage prior to the mature grain stage. Sorghum may be injured by Ban\'el. Specific Weed Problems Ye//ow Nuf sedge Yellow nutsedge is a perennial sedge with a triangular stem. It reproduces mainly by tubers. Regardless of the soil depth at which the tuber germinates, a basal bulb develops 1 to 2 inches under the soil surface. A complex system of rhizomes (underground stems) and tubers de- velops from this basal bulb. Yellow nutsedge tubers begin sprouting about May 1 in central Illinois. For the most effective control, soil-applied herbicides should be incor- porated into the same soil layer in which this basal bulb is developing. For soybeans, a delay in planting until late May allows time for two or three tillage operations to destroy many nutsedge sprouts. Tillage helps deplete food reserves in nutsedge tubers. Row cultivation is helpful. Preplant ap- plications of Lasso, Dual, or Vemam will also help. Lasso (alachlor) applied preplant incorporated at 3 to 4 quarts per acre (V2 quart more than for surface- applied rates) often gives good control of nutsedge. Dual (metolachlor) can be applied at 2 to 3 pints of 8E per acre to control nutsedge. Preplant treatment is preferred to treatment at the preemergence stage. Vemam 7E (vemolate) applied preplant at 3'/2 pints per acre is also effective against yellow nutsedge. Imme- diate incorporation is necessary with Vemam. Basagran (bentazon) is a postemergence treatment that can also help control nutsedge in soybeans. One quart per acre can be applied when nutsedge is 6 to 8 inches tall. A split application (two treatments) of Basa- gran has also been registered. Addition of a crop-oil con- centrate to Basagran may improve performance. For corn, preplant tillage before nutsedge sprouts is of little help in control. Timely cultivation gives some con- trol, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane (EPTC) or Sutan+ (butylate) at 4Vi to yV's pints per acre are effective for control of yellow nutsedge in com. They must be incorporated immediately. Lasso or Dual applied in com as for soybeans can also be quite effective. The combinations of Lasso, Dual. Sutan + , or Eradi- cane incorporated with atrazine may give better control of nutsedge while also controlling broadleaf weeds. Atrazine or Bladex (cyanazine) is used as a post emer- gence spray to control emerged yellow nutsedge when it is small. Split applications of atrazine plus oil have been more effective than single applications. Basagran can be used in corn in a manner similar to that for soy- beans. Lorox (Hnuron) directed postemergence spray has also given some control. Johnsongrass Johnsongrass can reproduce both from seeds and by rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the johnson- grass head begins to appear. Mowing, grazing, or culti- vating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, making them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or suppressed using certain herbicides in various cropping programs. Several preplant incorporated herbicides can provide control of johnsongrass seedlings in soybeans or corn (see the table at the end of this article) . Treflan (trifluralin), Prowl (pendimethalin), or Basa- lin (fluchloralin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnson- grass. They are used at IV2 to 2 times the normal rate each year for 2 years, and then either at the normal rate, or another suitable herbicide is used the third year before resuming a regular cropping sequence. Thorough pre- plant tillage and incorporation are necessary for satis- factory control. Be certain not to plant such crops as com or sorghum following application of these herbicides at the higher rates. Eradicane (EPTC) or Sutan+ (butylate) will sup- press rhizome johnsongrass in com when used at a rate of 7V3 pints per acre as a preplant incorporated treat- ment. However, this increase in rate also increases the risk of com injury. Dalapon can be used to treat emerged johnsongrass before planting com or soybeans. Apply 5 to 7 pounds per acre after the grass is 8 to 12 inches tall. Plow or disk after 3 days and then delay planting com or soybeans at least 1 week. See the label for sp)ecific intervals. Dalapon can also be used to control johnsongrass after wheat that is not double cropped or undersown with a 14 legume. A combination of mowing, timely dalapon ap- plication, and tillage has provided quite effective control of johnsongrass. Roundup (glyphosate) can be used as a spot treat- ment to control johnsongrass in com, soybeans, or sor- ghum. Apply 2 to 3 quarts when johnsongrass has reached the boot to head stage and is actively growing. Use of Roundup in wick or recovery-type sprayers is effective for control of johnsongrass in soybeans. (See section on directed postemergence herbicides for soy- beans. ) Roundup may be applied in small grain stubble when johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass Quackgrass is a perennial grass with shallow rhizomes. Most preemergence herbicides will not control it. Atrazine is quite effective when used as a split appli- cation in corn. Apply 2'/2 pounds of atrazine SOW per acre in the fall or spring and plow 1 to 3 weeks later. Another 2'/2 pounds per acre should be applied as a pre- plant or preemergence treatment. Postemergence appli- cation is usually less effective. A single treatment with 3% to 5 pounds per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. If more than 3 pounds of atrazine is applied per acre, do not plant crops other than com or sorghum the following year. Eradicane (EPTC) can be used to suppress quack- grass in corn where more flexibility in cropping sequence is desired. A rate of 4% pints per acre of Eradicane 6.7E can be used on light infestations, while TV's pints per acre is suggested for heavier infestations. There is some risk of com injury, especially at the higher rate. A tank mix with atrazine should improve control. Dalapon can be applied to quackgrass 4 to 6 inches tall in the spring at a rate of 8 pounds per acre. Plow after 4 days and delay planting com for 4 to 5 weeks. Up to 15 pounds of dalapon per acre may be used in the fall. Roundup (glyphosate) can be used for controlling quackgrass before planting either com or soybeans. Apply 2 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). Delay tillage for 3 or more days after application. Canada Thistle Canada thistle is a perennial weed that has large food reserves in its root system. There are several varieties of Canada thistle. They differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in corn. Banvel often is a little more effective than 2,4-D and may be used alone or in combination with 2,4-D. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in corn. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Can- ada thistle in soybeans or com when the thistles are 8 to 12 inches tall. Apply % to 1 quart per acre in a single application, or for better control make two applications of % to 1 quart per acre each, 7 to 10 days apart. Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow 3 or more days after application before tillage. Amitrole or Amitrole-T effectively controls Canada thistle, but can be used only in noncrop areas. Tordon (picloram) gives good control of Canada thistle, but soybeans and most other broadleaf plants are extremely sensitive to it. Use only on noncropland. Additional Information Not all herbicides and herbicide combinations avail- able are mentioned in this publication. Some are rela- tively new and are still being tested. Some are not con- sidered to be very well adapted to Illinois or are not used very extensively. For further information on field crop weed control, consult your county Extension adviser or write to the Department of Agronomy, N-305 Turner Hall, 1102 S. Goodwin Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. 15 Relative Effectiveness of Herbicides on Major Weeds This chart gives a general comparative rating. Under unfavorable conditions, some herbicides rated good or fair may give erratic or poor re- suhs. Under ver>' favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when se- lecting herbicides. Rate of herbicide used also will influence results. G = good, F = fair or variable, and P = poor. Grasses Broadleaf Weeds o hi U o fe C 13 S 3 en o CA e« C u ti be D. Si a ;. j Ui rt u b 2 S) be c c -^ O -TJ c ^ 5 y O & t7 "V n V V c 3 C be be U4 0) 'r 3 V ^ c« u ej U rt JZ 1! 3 C C C s o o o E tn >• < U •—J -M O a u J2 tl 4J d "O 3 ei cr JC to Si s be rt hJ ^ c a 'to S, S) ho :^ 0^ (ii^ T3 u u B •ZJ > SOYBEANS Preplant Treflan, Tolban, Prowl, Basalin F-G G G G G G G P F-P P P G P G P P P-F P Sencor, Lexone + dinitroaniline F G G G G G G P F F F-G G P G G F G F-G Vernam F G G G G G G F F-P P P F P G P P P F Preplant or Preemergence Amiben F-G G F-G F-G F-G F F P P P P-F G F-G G F-G F F-G F Lasso, Dual G G G G G P-F P-F F-G P P P F F-G G P-F P P-F P Lasso or Dual + Sencor or Lexone F G G G G P P F P F F-G G F G G F G F-G Lasso or Dual + Lorox' F G G G G P P P-F P F F G F-G G G F G F-G Lorox' F F F F F P P P P F F G P-F G G F G F-G Modown, Goal F F F F F P P P F-P P F G F G F P G F Sencor, Lexone' F F F F F P P P-F P F F-G G P G G F G F-G Postemergence Basagran F-G P P P P P P F P-F G G F P F F F G F-G Blazer F P-F P P-F P P P P F-G F G F F-G F-G F F G P Dyanap F P P P P P P P F G G F-G P-F F-G F F F P-F 2,4-DB P-F P P P P P P P F-G G P-F F P F F F P P Hoelon G F-G F F-P F P P P P P P P P P P P P P CORN Preplant Sutan+, Eradicane F-G G G G G F-G F-G F-G P P P P-F F G P P P F Sutan+ or Eradicane + atrazine, Bladex F-G G G G G F-G F-G F-G F-G F-CG G G ' • G G F G F-G Princep + atrazine G F-G F-G F F P P-F P F-G F-G G G G G G G G F Preplant or Preemergence Atrazine G F-G F P P P P F G F-G G G G G G G G F-G Banvel + Lasso or Dual F-G G G G G P P F P-F F F-G G G G G F G F Bladex F-G F-G F-G F-G G P P P F F-G G G G F G F-G G F Bladex + atrazine F-G F-G F F F-G P P P F-G F-G G G G G G F-G G F-G Lasso, Dual F-G G G G G P-F P-F F-G P P P F F G P-F P P-F P Lasso or Dual + atrazine or Bladex F-G G G G G P P F-G F-G F G G G G G F G F Prowl + atrazine or Bladex' F-G G G G G F F P F-G F G G G G G F G F-G Propachlor + atrazine or Bladex' G G G F-G F P P P-F F-G F G G G G G F G F Ramrod, Bexton, Propachlor' G G F F-G F P P P-F P P P F P G P P P P Postemergence Atrazine + oil F-G F-G G P P P P F G G G G G G G F G F-G Banvel G P P P P P P P G G G G G G G G G F Basagran G P P P P P P F P-F G G F P F F F G F-G Bladex F-G G G F F-G P P F F F-G G F G F-G G F G F 2,4-D F-G P P P P P P P G G F G F G G G P-F F-G ' Preemergence only 18M—1 1-81— 52388— rgm niz>/^ '''^'CULTURE imm 111* ptmy Of tt» 1983 Row Crop Wr 1 /^ A 1 i^ • 1 JUL 15 1983 Weed Lontrol LrUide This guide is based on the results of research con- ducted by the University of Illinois Agricultural Experi- ment Station, other experiment stations, and the U.S. Department of Agriculture. Consideration has been given to the soils, crops, and weed problems of Illinois. Rainfall, soil type, method of application, and formula- tion influence herbicide effectiveness. Under certain con- ditions some herbicides may damage crops to which they are applied. In some cases, herbicide residues in the soil may damage crops grown later. When selecting a herbicide, consider both the risk in- volved in using the herbicide and the yield losses caused by weeds. If cultivation and good cultural practices are controlling weeds, herbicides may be unnecessary. You can reduce risks by taking these precautions : • Apply herbicides only to those crops for which use has been approved. • Clean tanks thoroughly when changing from com to soybeans, especially when using a postemergence her- bicide. • Use recommended rates. Applying too much herbi- cide is costly and in addition may damage crops and cause illegal residues. Using too little herbicide can result in poor weed control. • Apply herbicides only at times specified on the label. Observe the recommended intervals between treatment and pasturing or harvesting of crops. • Wear goggles, rubber gloves, and other protective clothing as suggested by the label. • Guard against drift injury to nearby susceptible plants, such as soybeans, grapes, and tomatoes. Mist or vapors from 2,4-D, MCPA, and dicamba sprays may drift several hundred yards. Operate sprayers at low pressure with tips that deliver large droplets. Spray only on calm days or make sure air is not moving toward susceptible crop plants and ornamentals. • Apply herbicides only when all animals and persons not directly involved in the application have been re- m©¥e4 from the area. Avoid unnecessary exposure. y"^ • Check label for proper method of container disposal. Triple rinse, puncture, and haul metal containers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or burn them in an approved manner. • Return unused herbicides to a safe storage place University Ot Illinois at UtHiw OwipilBn promptly. Store them in original containers, away from unauthorized persons, particularly children. • Since manufacturers' formulations and labels are sometimes changed and government regulations modi- fied, always refer to the most recent product label. This guide has been developed to help you use herbi- cides as effectively and safely as possible. However, since no guide can remove all the risk involved, the University of Illinois and its employees assume no responsibility for results of using herbicides, even if they have been used according to the suggestions, recommendations, or direc- tions of the manufacturer or any governmental agency. Cultural and Mechanical Control Most weed control programs combine good cultural practices, mechanical weed control, and herbicide appli- cations. Good cultural practices to aid weed control in- clude preparation of a good seedbed, adequate fertiliza- tion, crop rotation, seeding on the proper date, use of the optimum row width, and seeding at the rate for optimum stands. Planting in relatively warm soils helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both corn and soybeans. If weed control is adequate during that period, corn and soybeans will usually compete quite well with most of the weeds that begin growth later. Narrow rows will shade the centers faster and help the crop compete better with the weeds. However, if herbi- cides alone cannot give adequate weed control, then keep rows wide enough to allow cultivation. Some of the newer herbicides are improving the chances of adequate control without cultivation. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Use the rotary hoe after weed seeds have germinated but before most have emerged. Operate it at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small Prepared by M. D. McGlamery, Professor of Weed Science, Ellery Knake, Professor of Weed Science, Dave Pike, Associate Agronomist, Allan Beuerman, Associate Agronomist, and F. W. Slife, Professor of Agronomy, all at the University of Illinois; with the assistance of George McKibben, Professor of Agronomy, Dixon Springs Agricultural Center, George Kapusta, Professor of Plant and Soil Science, Southern Illinois University, Carbondale, and Gordon Roskamp, Associate Professor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist, USDA, and Professor of Weed Science, and E. W. Stoller, Plant Physiologist, USDA, and Professor of Agronomy, both at the University of Illinois. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agricul- ture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbana-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. weeds. Cultivate shallow to prevent injury to crop roots. Avoid excessive ridging; it may hinder harvesting and encourage erosion. Herbicides can provide a convenient and economical means of early weed control by allowing delayed and faster cultivation. Furthermore, unless the soil is crusted, it is usually not necessary to cultivate at all when herbi- cides are controlling weeds adequately. Herbicide Incorporation Soil-applied herbicides are incorporated to minimize surface loss, reduce dependence upon rainfall, and pro- vide appropriate placement of the herbicide. Sutan+ and Eradicane are incorporated soon after application to minimize surface loss from volatization. Dinitroaniline herbicides such as Treflan and Prowl are incorporated within a few hours to minimize loss due to photode- composition and volatization. Triazine herbicides such as atrazine and Bladex and acetanilide herbicides such as Lasso and Dual may be incorporated to minimize de- pendence upon timely rainfall, but time of incorporation for them is less critical since they are not lost so quickly from the soil surface. Incorporation should place the herbicide uniformly in the top 1 to 2 inches of soil for best control of small- seeded annual weeds that germinate from shallow depths. Slightly deeper placement may improve the control of certain weeds from deep-germinating seed under rela- tively dry conditions. The field cultivator and tandem disk place most of the herbicide one-half to two-thirds of the depth of operation. Thus for most herbicides the suggested depth of operation is 3 to 4 inches. Thorough incorporation with ground-drive implements may require two passes. Single-pass incorporation tends to result in streaked weed control, especially in wet soils. Single-pass incorporation may be adequate with some equipment, especially if rotary hoeing and cultivation are used to improve weed control. If the herbicide is suffi- ciently covered to prevent surface loss with the first pass, the second pass can be delayed until immediately before planting. The addition of a coil-tine or spike-tooth drag harrow or rolling baskets behind the disk or field culti- vator can help provide uniform mixing. The depth and thoroughness of incorporation depend upon the type of equipment, depth and speed of opera- tion, soil texture, and soil moisture. Field cultivators and tandem disks are common implements used for incorpo- ration. However, disk-chisels and other combination tools are being promoted and used in some areas. Fleid Cultivators Field cultivators are frequently used for herbicide in- corporation. They should have three or more rows of tool bars with an effective shank spacing of no more than 8 to 9 inches (a spacing of 24 to 27 inches on each of three tool bars) . The shanks can be equipped with points or sweeps. Sweeps usually give better incorporation, espe- cially when soil conditions are a little too wet or dry for optimal soil flow and mixing. Sweeps for "C" shank culti- vators should be at least as wide as the effective shank spacing. The recommended operating depth for the field culti- vator is 3 to 4 inches. It is usually necessary to operate only deep enough to remove tractor-tire depressions. The ground speed should be at least 6 mph. The field culti- vator must be operated in a level position so that the back shanks are not operating in untreated soil, which would result in streaked weed control. Two passes are recom- mended to obtain uniform weed control. If single-pass incorporation is preferred, the use of wider sweeps or narrower spacing will increase the probability of obtain- ing adequate weed control. Tandem Disks Tandem disk harrows invert the soil and usually place the herbicide deeper in the soil than most other incorpo- ration tools. Tandem disks used for herbicide incorpora- tion should have disk blade diameters of 22 inches or less and blade spacings of 7 to 9 inches. Larger disks are con- sidered primary tillage tools and should not be used for incorporating herbicides. Spherical disk blades give better herbicide mixing than conical disk blades. Tandem disks usually place most of the herbicide in the top two-thirds of the depth of operation. For most herbicides, the suggested operating depth is from 3 to 4 inches. Recommended ground speeds are usually be- tween 4 and 6 mph. The speed should be sufficient to move the soil the full width of the blade spacing. Lower speeds can result in herbicide streaking. Chemical Weed Control Plan your chemical weed-control program to fit your soils, crops, weed problems, and farming operations. Herbicide performance depends on the weather and on wise selection and application. Your decisions on herbi- cide use should be based on the nature and seriousness of your weed problems. Corn or soybeans occasionally may be injured by some of the herbicides registered for use on them. However, the benefits from weed control are usually much greater than the adverse effects. Crop tolerance ratings for var- ious herbicides are given in the table on the last page of this publication. Com or soybeans under stress from soil crusting, depth of planting, or adverse weather are more subject to herbicide injury. Plants injured by a herbicide are likely to be more subject to disease. Apply the herbicide at the time specified on the label. Select and apply herbicides at the correct rate in order to reduce crop injury. The application rates for most herbi- cides vary with soil texture and organic matter. You must also consider the kinds of weeds likely to be present. The herbicide selectivity table at the end of this guide indicates the susceptibility of our most common weed species to herbicides. Crop planting intentions for the next season must also be considered. Where high rates of atrazine or simazine are used, you should not plant soybeans, small grains, alfalfa, or vegetables the following year. If you are con- sidering planting wheat after soybeans, be sure that the application of Treflan or similar herbicides for soybeans is uniform and sufficiently early to reduce the risk of injury to wheat or corn following soybeans. Refer to the herbicide label for cropping sequence information. Names of Some Herbicides Trade Common (generic) AAtrex, Atrazine atrazine Alanap naptalam Amiben chloramben Banvel dicamba Basagran bentazon Basalin fluchloralin Bicep metolachlor + atrazine Bladex cyanazine Blazer acifluorfen Bronco alachlor + glyphosate Butoxone, Butyrac 2,4-DB Dowpon M dalapon Dual metolachlor Dyanap naptalam plus dinoseb Eradicane Extra EPTC Evik ametryn Furloe Chloro IPC chlorpropham Fusilade fluazifop-butyl Goal oxyfluorfen Hoelon dichlofop Laddok bentazon + atrazine Lasso alachlor Lorox linuron Milogard propazine Modown bifenox Paraquat, Gramoxone paraquat Poast sethoxydim Princep, Simazine simazine Prowl pendimethalin Ramrod propachlor Rescue naptalam plus 2,4-DB Roundup glyphosate Sencor, Lexone metribuzin (several) 2,4-D Surfian oryzalin Sutan+ butylate Sutazine butylate plus atrazine Treflan trifluralin Vernam vernolate Vistar mefluidide Some herbicides have different formulations and con- centrations under the same trade name. No endorsement of any trade name is implied, nor is discrimination against similar products intended. Herbicide Combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package mix," while others are tank mixed. Tank mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifiable concentrate (EC) formulations with wettable powder (WP), water dispersible liquid (WDL), or water dis- persible granule (WDG) formulations. These problems can sometimes be prevented by using proper mixing pro- cedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides. If using liquid fertilizers, check compatibility in a small lot before mix- ing a tankful. The addition of compatibility agents may be necessary. Wettable powders, WDGs, or WDLs should be added to the tank before ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to pre- vent accumulation of material on the sides and the bottom of the tank. Some of the herbicide combinations that have been registered are listed below. The herbicide listed first is the one that carries label or supplemental instructions on mixing. The label of the other herbicide (s) may also have mixing instructions. Com Atrazine + Princep (PPI, Pre, NT/P, NT/R)^ Atrazine 4- propachlor (Pre, early Post) Banvel 4- atrazine (Post) Banvel 4- Lasso ( Pre, early Post) Banvel + 2,4-D (Post) Basagran 4- atrazine (Post) Bladex 4- atrazine (PPI, Pre, Post, NT/P) Bladex 4- atrazine -f- Lasso (PPI, Pre) Bladex 4- paraquat (NT) Bladex 4- Sutan4- (PPI) Dual + AAtrex (PPI, Pre, early Post, NT/P, NT/R) Dual 4- Princep (PPI, Pre, NT/P, NT/R) Dual 4- atrazine 4- Princep (PPI, Pre, NT/P, NT/R) Dual 4- Banvel (Pre, early Post) Dual 4- Bladex (PPI, Pre, NT/P) Eradicane 4- atrazine or Bladex (PPI) Eradicane 4- Bladex 4- atrazine (PPI) Lasso 4- atrazine (PPI, Pre, early Post, NT/P, NT/R) Lasso 4- Bladex (PPI, Pre, NT/R) Lasso 4- Princep (NT/R) Paraquat 4- atrazine (NT) Prowl 4- atrazine ( Pre, early Post) Prowl 4- Banvel (Pre) Prowl 4- Bladex (Pre, early Post) Sencor 4- atrazine 4- Dual or Lasso (Pre) Sencor 4- Bladex + Dual or Lasso (Pre) Sutan4- 4- atrazine (PPI) Sutan4- 4- atrazine 4- Bladex (PPI) Soybeans Alanap + 2,4-DB (Post) Amiben + Lasso (PPI, Pre) Amiben + Lorox (Pre) Amiben + Sencor (Pre) Amiben + Surflan (Pre) Amiben + Treflan or Basalin (PPI) Amiben 4- Dual + Sencor or Lexone (PPI, Pre) Amiben + Lasso + Sencor or Lexone (PPI, Pre) Amiben + Treflan + Sencor or Lexone (PPI) Basagran + 2,4-DB (Post) Basalin -|- Sencor or Lexone (PPI) Blazer + 2,4-DB (Post) Dual + Amiben (PPI, Prel Dual + Dyanap (Pre, earlv Post) Dual + Lorox (Pre, NT/P, NT/R) Dual + Sencor or Lexone (PPI, Pre, NT/P, NT/R) Dyanap + Lasso (Pre, early Post) Furloe + Lasso (Pre) Furloe + Treflan (PPI) Furloe + Vemam (PPI) Goal 4- Lasso (Pre, NT/P) Lasso + Lorox (Pre, NT/P, NT/R) Lasso + Lexone or Sencor (PPI, Pre, NT/P, NT/R) Lorox + 2,4-DB (Post — directed) Modown + Lasso (PPI, Pre) Modown + Treflan (PPI) Paraquat + Lorox (NT) Paraquat + Sencor (NT) Prowl + Amiben (PPI, Pre) Prowl + Amiben + Sencor or Lexone (PPI, Pre) Prowl + Lorox (Pre, NT/P) Prowl + Sencor or Lexone (PPI, Pre, NT/P) Sencor 4- .Amiben (Pre) Sencor + Dyanap fPre) Sencor + Lasso + Dyanap (Pre) Sencor + 2,4-DB (Post — directed) Sencore or Lexone + Treflan (PPI) Sencor + Treflan (PPI) + Sencor (Pre) Surflan + Dyanap (Pre) Surflan + Lorox (Pre, NT/P) Surflan + Sencor or Lexone (Pre, NT/P) Vemam + Treflan or Basalin ( PPI ) Vemam 4- .Amiben (PPI) 1 PPI = preplant incorporated, Pre = preemergence, Post = postemergence, NT = no-till, NT/P = no-till with Paraquat, NT/R = no-till with Roundup. The user can apply t^v•o treatments of the same herbi- cide (split application) , or he can use two diff"erent ones, provided such uses are registered. Applying two herbi- cides at diff'erent times is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant application might be followed by a preemergence application, or a soil-applied treatment might be followed by a jxjstemer- gence treatment. One herbicide may be broadcast while the other is banded or directed. Herbicide Rates Herbicide rates vary according to the time of applica- tion, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence application than for pre- plant incorporated application. Postemergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary dep>ending on the size and species of the weeds and on whether an adjuvant is specified. Rates for combinations are usually lower than for herbicides used alone. The rates for soil-applied herbicides usually var)' de- pending on the texture of the soil and the amount of organic matter it contains. For instance, light-colored, medium-textured soils with little organic matter require relatively lower rates of most herbicides than do the dark- colored, fine-textured soils ^v'ith medium to high organic matter. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemer- gence rather than soil-applied herbicide," depending on the herbicide and its adaptation and on crop tolerance. The rates given in this publication are, unless other- wise specified, broadcast rates for the amount of formu- lated product. If you plan to band or direct herbicides, adjust the amount per crop acre according to the per- centage of the area actually treated. Many herbicides have several formulations with different concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formulations. Postemergence Herbicides Postemergence herbicides applied to growing weeds generally have foliar rather than soil action. The rates and timing of applications are based on weed size and climatic conditions. Weeds can usually be controlled with a lower application rate when they are small and tender. Larger weeds often require a higher herbicide rate or the addition of a spray additive, especially if the ^veeds have developed under drouth conditions. Herbicide pene- tration and action are usually greater when the tempera- ture and relative humidity are high. Rainfall occurring too soon after application (1 to 8 hours, depending on the herbicide) can cause poor weed control. Translocated (hormone) herbicides can be effective with partial foliar coverage, whereas contact herbicides require complete coverage. Foliar coverage increases as \vater volume and spray pressure are increased. Spray nozzles that produce small droplets also improve cover- age. For contact herbicides, 20 to 40 gallons of water per acre are often recommended for ground application and a minimum of 5 gallons per acre for aerial application. Spray pressures of 30 to 50 psi are often suggested with flat-fan or hollow-cone nozzles to produce small droplets and improve canopy penetration. Such small droplets are quite subject to drift. The use of a surfactant or crop oil concentrate may be recommended to improve spray coverage. These spray additives will usually improve weed control but may increase crop injury. Spray additives may be needed only under drouth conditions or on larger weeds. Crop size limitations may be specified on the label to minimize crop injury and maximize weed control. If weeds are smaller than the crop, basal-directed sprays may minimize crop injury because they place more herbicide on the weeds than on the crop. If the weeds are taller than the crop, rope-wick applicators or recirculating sprayers can be used to place the herbicides on the top of the weeds and minimize contact with the crop. Follow the label directions and precautions for each herbicide. Conservation Tillage and Weed Control Efficient production with any tillage system is highly dependent upon effective weed control. Weed control problems have probably been the primary deterrent to widespread adoption of conservation tillage. However, the availability of a wide spectrum of effective herbicides has made acceptable weed control possible with conserva- tion tillage. Conservation tillage protects the soil from erosion by leaving the soil surface rough and covered with crop residue. For effective erosion control it is essential that the soil surface be protected in the spring before and after corn or soybeans are planted. Satisfactory weed control is more difficult with crop residue or clods on the soil surface because ( 1 ) the resi- due or clods may interfere with herbicide distribution or incorporation, (2) most weeds are not deeply buried, resulting in heavier weed infestations, and (3) the roots of perennial weeds are not disturbed as much. Increased weed pressure coupled with decreased herbi- cide performance requires better herbicide management. You must exercise greater care in choosing herbicides and application rates. Preemergence herbicides require less secondary tillage than preplant-incorporated treatments, but they are more dependent upon timely rainfall. Soil- applied herbicides may require a higher application rate for satisfactory control with conservation tillage. In any case, do not use a higher rate than indicated on the label instructions. Effective postemergence herbicides may be a logical choice when available, as they depend upon foliar action rather than soil action. No-Till and Double-Crop Corn and soybeans are sometimes produced without seedbed preparation, either in last year's crop residue (no- till) or as a second crop after small grain harvest or forage removal (double-crop). The no-till concept of planting has greatly improved the probability of success of double-cropping by conserving soil, soil moisture, and time. No-till herbicides must control both vegetation existing at planting and seedling weeds that germinate after planting. Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop. or weeds that emerge in the previous years' crop stubble before planting. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor, especially if herbicides are applied before regrowth. Labeled applications of 2,4-D, Roundup, or Banvel can improve control of broadleaf perennials when used in registered crops, such as corn or sorghum. Several precautions should be observed in no-till crop- ping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact from herbicide sprays. (Several herbicide labels give planting depths necessary to avoid possible injury.) Pre- emergence applications of the herbicide treatment may give better weed control than preplant applications since the planting process may expose untreated soil contain- ing viable weed seed. The total reliance on chemical weed control and large amounts of crop residue present under no-till cropping systems may require that the higher labeled herbicide rates be used to obtain accept- able weed control. Postemergence herbicides may be needed in no-till soybeans. Paraquat or Gramoxone (1 or 2 pints per acre) plus a nonionic surfactant at V2 pint per 100 gallons of diluted spray is generally used to "knock down" existing foliage before crop emergence. Smartweed, giant ragweed, and fall panicum may not be controlled if they are over 10 to 12 inches high and if no rain occurs to "activate" the residual herbicides. A minimum of 40 gallons or more of spray per acre is suggested to insure adequate coverage of the foliage. Paraquat and Gramoxone are restricted-use pesticides. Roundup (3 pints per acre) should be considered as an alternative treatment for control of the foliage prior to crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can translocate to the roots to give better con- trol of perennials. Use 20 to 30 gallons of spray volume per acre. Bronco is a formulated mixture of glyphosate (Roundup) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Do not apply in liquid fertilizers. No-tiil Corn Herbicides registered with paraquat plus atrazine are Dual, Lasso, Princep, and Bladex. Dual plus Princep, atrazine plus Princep, and Bicep are also registered with paraquat. These combinations give better control of annual grasses than atrazine or Bladex plus paraquat. Herbicides registered with Roundup plus atrazine or Princep are Dual and Lasso. Roundup is also registered with atrazine plus Princep, atrazine plus Princep plus Dual, Lasso plus Bladex, and Bicep for use in no-till com. Bronco is registered for use with atrazine, Bladex, or Princep. The section entitled "Herbicides for Corn" pro- vides more information on these products. No-till or Double-Crop Soybeans Preemergence herbicides registered in soybeans as tank mixes with paraquat (1 to 2 pints per acre) are Lorox, Sencor, or Lexone alone or in combination with Lasso, Dual, Prowl, or Surflan. Goal plus Lasso is also cleared with paraquat. Registered tank mixes with Roundup are Lasso or Dual in combination with Lorox, Sencor, or Lexone. Bronco is registered with Lexone, Lorox, or Sencor. See the section entitled "Herbicides for Soy- beans" for more information on these products. Herbicides for Corn All herbicides mentioned in this section are registered for use on field corn and also on silage corn unless other- wise specified. Herbicide suggestions for sweet corn and popcorn may be found in Circular 907, 1983 Weed Man- agement Guide for Commercial Vegetable Growers. Growers producing hybrid seed corn should check with the contracting company or inbred producer about tol- erance of the parent lines. Preplant Incorporafion Preplant application should be made anytime during the 1 or 2 weeks before planting. Incorporation should distribute the herbicide uniformly in about the top 2 inches of soil. Do not apply herbicides too early or in- corporate them too deeply. Sutan4- (butylate) or Eradicane (EPTC) may be applied anytime during the 2 weeks prior to planting. It is best to incorporate them soon after application or preferably as they are being applied. Both herbicides are formulated with a crop safening agent to decrease the risk of corn injury. However, injury can still occur when growing conditions are unfavorable or when certain hy- brids are used. Sutan+ and Eradicane control the seedlings of annual grasses, shattercane, and johnsongrass. Eradicane will suppress wild proso millet. The suggested rate for these herbicides used alone or in combinations is 4% to 7'/3 pints per acre. Use the higher amount on heavy infestations of wild cane or yellow nutsedge or to suppress rhizome johnsongrass (see section on specific weed problems). A lower rate may be used on sandy soils. You can control broadleaf weeds by tank mixing with atrazine or Bladex or by sequencing with an appropriate postemergence herbicide. The rate for combinations of Sutan+ or Eradicane with atrazine is VA to 2 pounds of atrazine 80\V (2 to 3 pints of 4L) , while the rate for Bladex is P/2 to 3M pounds of Bladex SOW (2 to 6 pints 4L) . A combination of atrazine plus Bladex with Sutan+ or Eradicane is also registered. Eradicane Extra includes an extender (microbial in- hibitor) to lengthen weed control when Eradicane has been used the previous year. Herbicide combinations are the same as with Eradicane. Sutazine+ is a prepacked combination of 4.8 pounds of Sutan+ and 1.2 pounds of atrazine per gallon. Sug- gested application rates are 7 to IOV2 pints per acre. Preplant or Preemergence Herbicides Incorporation of the following herbicides is optional depending upon the weeds to be controlled and the likeli- hood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 weeks prior to planting, or soon after planting. Preplant incorporation of these herbicides controls weeds more effectively if rain- fall is limited. Corn tolerance of atrazine and simazine is good, but earn-over to subsequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble, but just as persistent, as atrazine. Thus, Princep is usually preplant incorporated. Princep plus atrazine can be used in 1:1 or 2 : 1 combinations ; the total rate is the same as for atrazine used alone. The rate for atrazine used alone is 2'/2 to 3% pounds of atrazine BOW, 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex 90\VDG. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank mix combinations to improve broadleaf weed control. The rate for atrazine in combi- nations is V/2 to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to 1.8 pounds of AAtrex 90WDG. These rates may not provide adequate control of cockle- bur, morningglory, and velvetleaf but can reduce the risk of carryover. You can minimize earn-over injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil thoroughly before planting susceptible crops. The risk of carry-over is greater the year after a cool, dry growing season and on soils with pH over 7.3. If you use atrazine at more than 3 pounds of active ingredient per acre or if you apply after June 10, plant only corn or sorghum the next year. If you use atrazine in the spring and must replant, then plant only corn or sorghum that year. Do not plant small grains, small seeded legumes, or vegetables in the fall or spring. Soy- beans planted the year after an application of atrazine can also be affected from carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not persist in the soil as long as atrazine, but atrazine does have the advantage of better corn tolerance. Bladex controls fall panicum and giant foxtail, but not broadleaf weeds, better than atra- zine. Bladex can be combined with atrazine at 3:1, 2:1, or 1 : 1 ratios of Bladex to atrazine (see label for rates). The higher ratios will provide better grass control, while the 1 : 1 ratio will provide better broadleaf weed control. Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of corn injury. Rates are l'/2 to 5 pounds of Bladex 80 W, 1.2 to 4 quarts Bladex 4L, or 8 to 27 pounds of Bladex 15G per acre. You can lessen the risk of com injury by using reduced rates of Bladex in combinations. Bladex can be tank mixed with Lasso, Dual, Ramrod, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately before planting or after planting. Do not incorporate the Prowl or Ram- rod combinations. Three-way combinations of Bladex plus atrazine plus Lasso, Dual, Sutan+, or Eradicane are registered. The addition of a limited amount of atrazine should improve broadleaf control without increasing concern about carry- over. Lasso (alachlor) or Dual (metolachlor) can be ap- plied preplant incorporated or at the preemergence stage. Preplant incorporation will improve control of yellow nutsedge and can lessen dependence upon rainfall. In- corporation should distribute the herbicide evenly in the top 2 inches of soil. Lasso and Dual control annual grasses and help con- trol yellow nutsedge. You can improve broadleaf weed control by using atrazine or Bladex in preplant combina- tions or by using atrazine, Bladex, or Banvel in preemer- gence combinations. Lasso can be applied anytime during the week before planting corn and incorporated evenly into the top 2 inches of soil, or it can be used immediately after plant- ing. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate for the soil if you plan to incorporate Lasso. Dual can be applied anytime during the 2 weeks prior to planting corn and incorporated into the top 2 inches of soil, or it can be used immediately after planting. The rates are IV2 to 3 pints of Dual 8E per acre. Lasso or Dual plus atrazine can be applied preplant incorporated or after planting until corn is 5 inches tall and grass weeds are no larger than the two-leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is l'/2 to 2'/2 quarts of Lasso or 1V4 to 2V2 pints of Dual 8E plus IV2 to 2'/2 pounds of atrazine SOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds of AAtrex 90WDG. Dual is also cleared in a combina- tion with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atrazine. Bleep contains 2'/2 pounds of metolachlor (Dual) and 2 pounds of atrazine per gallon. The rate is 2 to 4 quarts per acre. Lasso/atrazine (flowable) con- tains 2'/2 pounds of alachlor (Lasso) and l'/2 pounds of atrazine per gallon. The rate is 3'/2 to 4!/2 quarts per acre. Dual or Lasso plus Bladex can be applied prior to planting and incorporated, or they can be applied during the preemergence stage after planting. The rate is 2 to 2'/2 quarts of Lasso 4E or VA to 2'/2 pints of Dual 8E plus 1 to 3 pounds of Bladex BOW or 1.6 to 4.8 pints of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Preemergence Herbicides Banvel (dicamba) plus Lasso or Dual can be applied after planting until com is 3 inches high, but before grasses reach the two-leaf stage. The addition of Banvel improves control of broadleaf weeds without creating a risk of carryover injury. Banvel may injure corn, espe- cially if recommended rates are exceeded, applications are not accurate and uniform, or if corn is planted too shallow (less than l'/2 inches). Do not use this treatment on coarse-textured soils or soils that are low in organic matter. The rate on soils with over 2'/2 percent organic matter is 1 pint of Banvel plus 2'/2 quarts of Lasso 4E, or 2 to 2V^ pints of Dual 8E per acre. Ramrod (propachlor) can be applied alone or with atrazine after the corn is planted but before grasses reach the two-leaf stage. Granular formulations should be ap- plied before crop or weeds emerge. Ramrod performs well on soils with over 3 percent organic matter. Ramrod is irritating to the skin and eyes, so observe label precautions. Corn tolerance is good. It controls annual grasses and pigweed. The rate is 4 to 6 quarts of Ramrod 4L or 20 to 30 pounds of 20G per acre. Ramrod can be mixed with atrazine or Bladex to im- prove broadleaf weed control. The rate is either 2V2 to 4 quarts of 4L plus l'/2 to 2 pounds of atrazine 80W (1.2 to 1.6 quarts of 4L) or VA to 2 'A pounds of Bladex 80 W (1.2 to 1.8 quarts of 4L) per acre. Prowl (pendimethalin) is registered only for use on corn after planting. Incorporation of Prowl may result in serious corn injury. Use only where it is possible to cover seed adequately with soil. Prowl can control annual grasses and pigweed and provides some control of smart- weed and velvetleaf. You can improve broadleaf weed control by combining Prowl with atrazine, Bladex, or Banvel. Prowl plus atrazine or Bladex may be applied in the early postemergence period before grasses are in the two-leaf stage. These combinations may also help reduce the competition from wild proso millet. However, avoid postemergence application when corn is under stress from cool, wet weather; otherwise, corn injury may result. The rate for such combinations is 1 to l'/2 quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than 1 V2 percent organic matter. Sencor (metribuzin) is registered for preemergence use in corn in three-way combinations. The rate is V2 pound of Sencor 50W, V2 pint of Sencor 4L, or '/s pound of Sencor 75DF per acre ('/4 pound of active ingredient per acre) . Sencor can be used at this rate in combination with Lasso or Dual plus atrazine or Bladex. Applying Sencor at this rate with the atrazine or Bladex may im- prove velvetleaf control but may also increase the poten- tial for corn injury, especially with Bladex. Do not use this combination on coarse-textured soils, soils containing less than 2 percent organic matter, or soils with a pH of 7.0 or higher. Postemergence Herbicides Lasso, Dual, Ramrod, Prowl plus Bladex or atrazine, or Lasso or Dual plus Banvel can be used on corn be- tween the preemergence and very early postemergence stages (see preemergence section). To get satisfactory control apply before grasses reach the two-leaf stage. Banvel plus atrazine can be applied up to 3 weeks after planting but before annual grasses are V/2 inches high. The rate is 14 pint of Banvel plus Hi to 2 pounds of atrazine SOW or 1 to 1.6 quarts of atrazine 4L. Atrazine can be applied before grass weeds are more than VA inches high. Many annual broadleaf seedlings are more susceptible than grass weeds and may be treated until they are up to 4 inches tall. The addition of oil-surfactant mixes or surfactants has generally increased the effectiveness of postemergence atrazine. Crop-oil concentrates ''80 percent oil and 20 percent surfactant > are used at the rate of 1 quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or about 1 pint per acre. Results with the oil-surfactant mixes have generally been better than those with surfactants. Applications of atrazine and oil sometimes damage com that has been under stress from prolonged cold, wet weather, or other factors. Do not use more than 2'/2 pounds of atrazine SOW or 2 quarts of atrazine 4L per acre if you mix with oil or oil concentrate. Do not add 2,.4-D to the atrazine-oil treatment or severe injun.- may result. Mix the atrazine with \vater first and add the oil last. If atrazine is applied after June 10, do not plant any crop except com or sorghum the next year. Bladex (cyanazine) can be applied through the four- leaf stage of com growth but before weeds exceed l'/2 inches in height. The rate is l'/2 to 2'/2 pounds of Bladex 80\V per acre. Do not use Bladex 4L, as it contains oil and can increase the potential for injur)-. A mixture of Bladex plus atrazine is also registered for postemergence use. Injun,- to com may occur under cold, adverse grow- ing conditions. The injur\- may only be temporan.- yellow- ing but can be more severe. Under drouthy conditions certain agricultural surfactants or vegetable oils may be added to Bladex 80\V to improve weed control. Do not use petroleum crop oils or apply with liquid fertilizers for postemergence application. Do not apply Bladex post- emergence to com under severe stress. Banvel or Banvel II (dicamba) can be applied from emergence until com is 36 inches tall. Banvel can be used at a rate of V2 to 1 pint per acre anytime after emergence until com is 5 inches high. Banvel II is preferred at 1 pint per acre for applications on com from 5 to 36 inches tall. The best time to apply is at the first flush of broad- leaf weeds and before the com is 5 inches tall. Banvel should be used in a sequential treatment following a grass herbicide such as Lasso, Dual, or Sutan-j-. Such timing allows for better crop tolerance than the pre- emergence treatments with Banvel, it permits application at a higher rate than the later postemergence treatment, and it diminishes the likelihood of significant injury to nearby soybeans. Banvel should be applied before soybeans in the area are 10 inches high. Soybean yields are seldom reduced when slight injur)' occurs early. However, yields can be reduced if severe injurs- occurs when soybeans are bloom- ing or during pod fill. Banvel also can injure other sus- ceptible plants, such as vegetables and ornamentals. Use extreme caution to avoid injurs- to desirable plants from either contaminated sprayers or drift of Banvel from treated areas. Banvel II or Banvel may be applied until com is 3 feet high or until 15 days before tasseling. When spraying near soybeans, do not spray com after it is 2 feet high. If com is more than 8 inches high, drop nozzles give better weed coverage, reduce drift, and lessen the chance of crop injur)-. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com and risk of injun.- to com is reduced. The broadcast rate is V2 pint per acre of Banvel or 1 pint per acre of Banvel II. Do not use Banvel on sweet com, popcorn, or seed corn. Do not graze or harvest com for dain,- feed before the ensilage fmilk) stage. A mixture of 1 2 pint of Banvel plus 1 2 pint of 2,4-D amine '4 pounds per gallon) per acre may present less risk of corn injur\- than 2,4-D alone. Use drop nozzles on corn more than 8 inches high when using the Banvel- plus-2,4-D mixture. 2,4-D is an economical and effective treatment for controlling many broadleaf w-eeds in com. Use drop nozzles if com is more than 8 inches high to decrease the possibility of injun.-. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com. Do not apply 2,4-D to com from tasseling to dough stage. .-Vfter the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-D's by air or high clearance equipment to control late-germinating broadleaf weeds that may interfere with han-est, or to suppress certain perennial weeds. The suggested broadcast rate of acid equivalent per acre is Vs to V4 pound of ester formulations or Vz pound of amine. This would be ! 3 to '/: pint of ester or 1 pint of amine for formulations with 4 pounds of 2,4-D acid equivalent per gallon. The ester forms of 2.4-D can vaporize and injure near- by susceptible plants. This vapor movement is more likely with high-volatile than with lo\s--volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Corn is often brittle for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other ssmptoms of 2,4-D in- jurs- are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. High temperature and high humidits- will increase the potential for 2,4-D injurs-, especially if com is growing rapidly. If it is necessars- to spray under these condidons. it may be w-ise to reduce the rate by about 25 percent. Com hybrids differ in their sensiti\-it)-, and the proba- bilirs- of injurs- increases when com is under stress. Basagran (bentazon) is registered for postemergence use in com in a manner similar to that for soybeans see soybean section' . Since com is quite tolerant of Basagran, the addition of a crop-oil concentrate is considered rela- tively safe. Basagran is also cleared at the rate of 1 to l'/2 pints in combination with atrazine at 0.6 to 0.9 pound of SOW, 0.6 to 0.8 pound of 90WDG, or 1 to l'/2 pints of 4L per acre. Laddok is a formulated mixture of Basa- gran plus atrazine. The rate is 2.4 to 3.6 pints per acre. Oil concentrate is added at 1 quart per acre for control of annual broadleaf weeds only. The combination is more economical than Basagran alone and will reduce the carryover potential from atrazine alone. Postemergence Soil-Applied Herbicides Prowl, Treflan, and Lasso can be applied to the soil as postemergence treatments. It may be necessary to use drop nozzles to avoid interference from corn leaves and ensure uniform application to the soil. Prowl (pendimethalin) or Treflan (trifluralin) maybe applied to the soil and incorporated after field com is 4 (for Prowl) or 8 (for Treflan) inches high and up to the time of last cultivation. The field should be cultivated to control existing weeds and cover the roots at the base of the corn before application. The herbicide should then be thoroughly and uniformly incorporated into the top inch of soil. Prowl may not need incorporation if irriga- tion or rainfall occurs soon after application. Prowl can be combined with atrazine. These treatments may help to control late-emerging grasses such as shattercane, wild proso millet, or fall panicum, which can still cause problems. Lasso (alachlor) may be used as a soil-applied post- emergence treatment in corn grown for seed to help con- trol midseason annual grass weeds. Application should preferably be made after cultivation before weeds emerge and before the crop is 40 inches tall. Lasso plus atrazine is an alternative that can be used anytime from immediately after cultivation until weeds reach the two-leaf stage of growth and corn is 40 inches tall. Directed Postemergence Herbicides Directed sprays are sometimes needed for emergency situations, especially when grass weeds become too tall for control with cultivation. However, weeds are often too large for directed sprays to be effective. Directed sprays cannot be used on small corn because a height difference between corn and weeds is needed to keep the spray off the corn. Corn leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox (linuron) may be applied as a directed spray after corn is at least 15 inches high (free standing) but before weeds are 8 inches tall (preferably not more than 5 inches) . Lorox controls grass and broadleaf weeds. The broadcast rate is VA to 3 pounds of Lorox 50W per acre, depending on weed size and soil type. Add Sur- factant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the corn as much as possible. Consider this an emergency treatment. Evik SOW (ametryn) is registered for directed use when corn is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 21/2 pounds Evik 80 W per acre (broadcast) plus 2 quarts of surfactant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Herbicides for Soybeans Consider the kinds of weeds expected when you select a herbicide program for soybeans, especially when grow- ing soybeans in narrow rows. The herbicide selectivity table (see last page of this guide) lists herbicides and their relative weed control ratings for various weeds. Soybeans may be injured by some herbicides. However, they usually outgrow early injury with little or no effect on yield if stands have not been significantly reduced. Significant yield decreases can result when injury occurs during the bloom to pod fill stages. Excessively shallow planting may increase the risk of injury from some herbi- cides. Accurate rate selection for soil type is especially essential for Lorox, Lexone, and Sencor. Do not apply Lorox, Lexone, Sencor, or Modown after soybeans have begun to emerge. Follow label instructions as to rates, timing, incorporation, and restrictions. Preplant Herbicides Incorporation is required for Basalin, Treflan, and Vernam. Incorporation is optional for Amiben, Dual, Lasso, Modown, and Prowl when used alone and in some combinations. Dyanap, Lorox, and Surflan should not be incorporated. Incorporation can improve performance if rainfall is limited and may increase the effectiveness of Dual or Lasso in controlling nutsedge. Incorporation should distribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early applica- tion of the herbicide can cause significant reductions in weed control. Dinitroaniline herbicides registered for weed control in soybeans are Basalin, Treflan, Prowl, and Surflan. Basalin and Treflan should be incorporated because of their low solubility and because of surface loss through vaporization and photodecomposition. Incorporation is optional with Prowl, but variable weed control and soy- bean injury may result from preemergence applications. Do not incorporate Surflan (see preemergence section). Incorporation should distribute the herbicide evenly in the top 2 to 3 inches of soil (see label for implement set- tings). A deeper incorporation may improve shattercane and johnsongrass seedling control. Basalin, Prowl, or Treflan may be used for rhizome johnsongrass suppres- sion (see section on specific weed problems). The dinitroaniline herbicides control annual grasses, pigweed, and lambsquarters and may provide some con- trol of smartweed and annual momingglory. Prowl and Surflan may also partially control velvetleaf. However, acceptable control of most other broadleaf weeds requires combinations or sequential treatments with other herbi- cides. The dinitroaniline herbicides provide similar weed control, soybean tolerance, and persistence when recom- mended rates are used. Soybeans are sometimes injured by dinitroaniline herbi- cides. Plants that have been injured by incorporated treatments are stunted and develop swollen hypocotyls and shortened lateral roots. Such injuries are not usually serious. Plants injured by preemergence applications de- velop stem callouses at the soil surface, which can cause lodging and yield loss. Crops of com, sorghum, or small grains may be injured if they are grown subsequent to a soybean crop that has been treated with a dinitroaniline herbicide. The symp- toms are poor germination and stunted, purple plants with poor root systems. To avoid carryover use no more than the recommended rates. Also, be sure that applica- tion and incorporation are uniform. The likelihood of carryover increases with double cropping or late applica- tion and after a cool, dry season. Disking or chisel plow- ing provides for minimal dilution of herbicide residues. Treflan (trifluralin) can be applied alone anytime in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks prior to planting, while combinations with Amiben, Furloe, or Modown should be applied within a few days prior to planting. Incorpo- rate as soon as possible, but do not delay incorporation more than 24 hours (8 hours if soil is warm and moist) . The rate is 1 to 2 pints of Treflan 4E or 10 to 20 pounds of Treflan 5G per acre. Basalin (fluchloralin) can be applied anytime during the 8 weeks (alone) or 1 to 2 weeks (with Sencor or Lexone) prior to planting. Incorporate within 8 hours of application. The rate is 1 to 3 pints Basalin 4E per acre. Basalin can be combined with Sencor or Lexone to im- prove broadleaf weed control. Prowl (pendimethalin) can be applied within 60 days (alone) or 7 days (with Sencor or Lexone) prior to planting soybeans or applied after planting (see pre- emergence). Preplant treatments should be incorporated within 7 days of application. Mechanical incorporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, although rates for combinations with Sencor or Lexone are lower than when the herbicide is used alone. Sencor or Lexone (metribuzin) plus Basalin, Prowl, or Treflan can be tank mixed and applied within 7 to 14 days of planting. Incorporate uniformly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is V2 to 1 pound of 50W, V2 to 1 pint of 4L, or Vs to % pound of 75\VDG. Use the normal rate, or slightly less, of the dinitroaniline herbicide (see labels) . A Sencor application can also be split, one part being incorporated with Treflan and the other part applied before emergence. This method requires two applications but can give better broadleaf control and less injur)' than incorporating the same total amount of Sencor with Treflan in a single application. Amiben (chloramben) can be incorporated with Basa- lin, Treflan, or Prowl. The rate is 4 to 6 quarts of Amiben 28 per acre. Amiben can also be applied at the rate of 3 to 5 quarts per acre and incorporated with Treflan plus Sencor or Lexone as a three-way combination. Vemam (vemolate) controls annual grasses and pig- weed. It sometimes provides fair control of annual mom- ingglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vemam can be applied within 10 days prior to planting and should be incorpo- rated immediately. The broadcast rate is 2'/3 to 3V2 pints of Vemam 7E or 20 to 30 pounds of Vernam lOG per acre. Vernam plus Treflan is labeled at the rate of 1 pint of Treflan plus 2V3 to 3 pints of Vemam 7E per acre. The combination will reduce the risk of soybean injur)', but it may also decrease control of velvetleaf and yellow nutsedge. Other labeled combinations include Vemam plus Amiben, Basalin, or Lasso. Preplant or Preemergence Herbicides Lasso (alachlor) or Dual (metolachlor) can be ap- plied to soybeans preplant incorporated or during the preemergence stage. If applied prior to planting, apply Dual anytime within the 2 weeks prior to planting and Lasso within 1 week of planting. If rainfall is limited, incorporation can improve performance and increase yellow nutsedge control. Soybeans are quite tolerant of Lasso or Dual. The first to second trifoliate leaves often appear crinkled with a drawstring effect on the middle leaflet, but these syinptoms should not cause concern. Lasso or Dual controls annual grasses plus pigweed and can help control nutsedge and black nightshade. These herbicides can be combined with Lexone, Sencor, or Amiben (incorporated or preemergence) and with Lorox or Dyanap (preemergence only) to improve broadleaf weed control. The rate for Lasso is 2 to 4 quarts Lasso 4E or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is V/2 to 3 pints per acre. Use the higher amount for the soil \vhen incorporating or when black nightshade or yellow nutsedge are to be controlled. The rate for combi- nations is about 75 percent of that for the herbicide used alone (see labels). Amiben (chloramben) can control annual grasses plus many broadleaf weeds in soybeans when used at the full rate. Do not expect control of cocklebur or annual mom- ingglory. Control of velvetleaf and jimsonweed is often erratic. Amiben occasionally injures soybeans, but dam- age is not usually severe. Injured plants may be stunted and have abnormal, shortened roots. If rain does not occur within 3 to 5 days of an Amiben preemergence application, you should rotary hoe. Amiben is best suited to soils with over 2.5 percent organic matter. Amiben can be applied alone or with Dual, Lasso, or Prowl as a preplant-incorporated or preemergence treat- ment. Amiben can also be mixed with Lasso or Dual plus Sencor as a preplant or preemergence treatment. Amiben can be applied as a preemergence treatment with Lorox, Lexone, and Sencor. The Amiben broadcast rate alone is 20 to 30 pounds of lOG, 4 to 6 quarts of 2S, or 2.4 to 3.6 pounds of 75DS 10 per acre. The Amiben rate in combinations is 3 to 6 quarts of 2S (1.8 to 3.6 pounds of 75DS) per acre. Use the higher rate where black nightshade, velvetleaf, or common ragweed is a problem weed. Sencor or Lexone (metribuzin) can be applied any- time during the 1 to 2 weeks prior to planting and in- corporated with Basalin, Dual, Lasso, Prowl, or Treflan. Incorporation should distribute the herbicide evenly in the top 2 inches of soil. It can be applied preemergence by itself or with Amiben, Dual, Lasso, Prowl, Surflan or Dyanap. Sencor or Lexone can control many annual broadleaf weeds except annual momingglory. Control of giant rag- weed, jimsonweed, and cocklebur is marginal at the re- duced rates necessary to minimize soybean injury. One symptom of soybean injury is yellowing (chlorosis) of the lower leaves at about the first trifoliate stage or later; it may be followed by browning of leaves and death of plants depending upon the severity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with pH over 7.5. Accurate, uni- form application and incorporation are essential. Adjust rates accurately according to soil conditions. Do not apply to very sandy soil. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is Vi to 1 pound of SOW, Vz to 1 pint of 4L, or Vi to % pound of 75WDG. You can use the higher amount when you apply this treatment during the preemergence stage, either alone or sequentially after applications of a preplant herbicide. The higher amounts can improve broadleaf control but also increase the risk of soybean injury. Modown (bifenox) can control pigweed, lambsquar- ters, and smartweed and provide some control of velvet- leaf. Combinations with Treflan or Lasso will improve grass control. Modown 4F rates are 3 to 4 pints per acre when used alone in a preemergence application or pre- plant incorporated with Lasso or Treflan. For preemer- gence applications with Lasso, the rate is 2'/2 to 3 pints per acre. For preplant incorporation, the application should be made within 2 to 3 days of planting, and in- corporation should place the herbicides evenly into the top 1 to 2 inches of soil. Do not apply Modown after soy- beans begin to emerge. Soybeans may show stunting from Modown, especially from preemergence use followed by cold, wet soil condi- tions during early growth stages. Injury symptoms are cupping and crinkling of the first few leaves. Soybean injury is usually not reflected in yield. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan or Vemam; or it can be ap- plied preemergence by itself or with Lasso to improve smartweed control. Preplant application should be done within a few days of planting soybeans, and incorporation should distribute the herbicide uniformly in the top 1 to 2 inches of soil. The rate in sequential or tank mix combi- nations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preemergence Herbicides Lorox (linuron) is best suited to silt loam soils that contain 1 to 3 percent organic matter. Do not apply to very sandy soils. Lorox controls broadleaf weeds better than grass weeds. It does not control annual moming- glory, and control of cocklebur and jimsonweed is vari- able. Accurate and uniform application, and proper rate selection are necessary to minimize the risk of crop injury. Tank-mix combinations allow the use of a reduced rate of Lorox to decrease the risk of soybean injury, but may also decrease the degree of weed control. Lorox is registered in tank-mix combinations with Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of Lorox in these combinations is 1 to 1 Vz pounds of Lorox 50W or V2 to % pint of Lorox 4L on silt loam soils with less than 3 percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if there is adequate rainfall. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after application. Do not use on soils of more than 5 percent organic mat- ter. The rate is 1 to 2 pounds per acre of Surflan 75W (% to IV2 quarts 4L) used alone or % to 1% pounds of Surflan 75W in combinations. Surflan can be tank mixed with Amiben, Lorox, Lexone, Sencor, or Dyanap to im- prove broadleaf weed control. Surflan may cause stem callousing, which can lead to soybean lodging. Do not allow Surflan to contact the soybean seed. Prowl can be applied preemergence in combination with Amiben, Lexone, Lorox, or Sencor. When applied to the soil surface. Prowl may cause stem callousing, which can lead to soybean lodging. (See preplant section for more information.) Dyanap (dinoseb plus naptalam) can be applied to soybeans from the time they are planted until the uni- foliate leaves of the seedling unfold and expose the growing point. A tank mix of Dyanap plus Lasso, Dual, or Surflan is registered to improve grass control. Dyanap can also be tank mixed with Lasso plus Sencor. The Dyanap rate is 4 to 6 quarts per acre for preemergence application. CJoal (oxyfluorfen) is labeled for preemergence use in no-till soybeans with paraquat in a two-way combina- tion and with paraquat plus Lasso in a three-way combi- nation. Rates in these combinations are 1 quart of Goal, 1 pint of paraquat, and 2 quarts of Lasso per acre. Postemergence Herbicides In the past, most farmers have placed primary empha- sis on controlling weeds early with preplant or preemer- gence applications, and have considered postemergence applications as a backup measure when control from earlier treatments was not adequate. Research suggests, however, that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after planting. The trend toward reduced tillage could encourage greater emphasis on postemergence treatments. Postemergence herbicides are most effective when their 11 use is part of a planned program, and when they are applied while the weeds are young and tender. They should not be considered simply an emergency treatment. It is especially important to use timely treatments when using postemergence herbicides in narrow-row soybeans. Postemergence herbicides are often the best choice for controlling certain problem weeds such as cocklebur, annual momingglory, and volunteer corn. Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf. It is weak on pigweed, lambsquarters, and annual morning- glory. It can be used for control of yellow nutsedge and Canada thistle but not of annual grasses. The suggested rate for Basagran is % to 1 quart per acre, depending on weed size and species. Application should be done when weeds are small (2-3 inches) and actively growing. These conditions usually exist when the soybeans are in the unifoliate to second trifoliate stage. Spraying during warm sunny weather can also improve performance. Do not spray if rain is expected within 8 hours. Use a minimum of 20 gallons of water per acre in order to get complete weed coverage. Adding a crop-oil concentrate to Basagran may increase performance, par- ticularly on yellow nutsedge, velvetleaf, and morning- glory, but may cause some soybean injury. Momingglory up to 10 inches long can be controlled with the addition of 2 fluid ounces of 2,4-DB with Basagran. Do not add crop oil when mixing with 2,4-DB. Blazer (acifluorfen) can be used to control annual momingglory, pigweed, black nightshade, and jimson- weed. Under ideal conditions it may also help control small escaped annual grasses. The rate is 2 pints of Blazer 2S per acre when broadleaf weeds are at the 2- to 4-inch stage and actively growing. Cocklebur and momingglory control can be improved with the addition of 2 fluid ounces of 2,4-DB (Butyrac or Butoxone). Application should be made when cocklebur and momingglory are not more than 10 to 12 inches tall or long and soybeans have at least five trifoliate leaves. Blazer is primarily a contact herbicide. Leaf bum often occurs, but the crop usually recovers within 2 to 3 weeks. Suggested spray volumes are 20 to 40 gallons of water per acre applied with a spray pressure of 40 psi. Surfactants or crop oil concentrates are not recommended with Blazer. Do not spray if rain is expected within 6 hours. Dyanap (dinoseb plus naptalam) can be applied to soybeans after the second trifoliate leaf opens until beans become 20 inches tall. Two to 3 quarts per acre is recom- mended for control of cocklebur, jimsonweed, smartweed, and annual momingglory less than 3 inches tall and four quarts per acre if weeds are 3 to 6 inches tall. A split application of 2 quarts at the second trifoliate stage followed by 2 quarts 10 to 14 days later is recommended for severe weed infestations. Best results are obtained by using high pressure (40 to 60 pounds per square inch) and 8 to 10 gallons of water per acre. Use 5 gallons of water for aerial applica- tion. Although leaf bum can occur, the crop usually re- covers within 2 to 3 weeks with little or no yield loss. Do not apply Dyanap to wet soybean foliage or if rain is expected within 6 hours. Do not add a surfactant. Amiben (chloramben) can be applied at 5 to 6 quarts per acre when soybeans are in the cracking to second trifoliate stage of growth. This treatment may control or suppress velvetleaf or smartweed that is less than 4 inches tall. Alanap (naptalam) plus 2,4-DB can be used for emer- gency control of cocklebur and giant ragweed. Apply when soybeans are about 18 inches tall but before mid- bloom stage. Rates are 2 to 3 quarts of Alanap plus 3 to 4 fluid ounces of Butyrac 200 or Butoxone SB per acre. A nonionic surfactant should be added at the rate of 2 quarts per 100 gallons of water. Rescue is a formulated mixture of Alanap plus 2,4-DB for use at 2 to 3 quarts per acre. Expect some soybean injury from this treatment. Ground application should be at 10 to 20 gallons of spray volume per acre. Use hollow-cone nozzles positioned 18 to 24 inches above the soybeans or weeds. Maintain spray pressure at 40 to 50 psi. Hoelon (dlchlofop) can control volunteer corn and small annual grass weeds. Application should be made when volunteer com has all emerged but is less than 10 inches tall. Annual grass weeds should be in the one- to four-leaf stage. The rate for volunteer com is 2% to 3'/3 pints per acre and for annual grasses is 2 to 3'/3 pints per acre. In most cases use Vs gallon of Hoelon per acre. Thorough spray coverage is important, so use a minimum of 20 gallons of water per acre and a minimum spray pressure of 30 psi. Do not tank mix Hoelon with other postemergence herbicides. Hoelon is a restricted use herbicide. Poast (sethoxydim) is a selective postemergence her- bicide for grass control in soybeans. It was labeled for experimental use in 1982 and will probably be given full registration in 1983. If registered, Poast can be used at the rate of 1 pint per acre on annual grasses, volunteer corn, and shattercane. Oil concentrate should be used at the rate of 1 pint per acre for aerial application or 2 pints per acre for ground application. Use a minimum of 20 gallons of water per acre with 40 psi pressure for ground application and a minimum of 5 gallons of water for aerial application. Higher water volumes are sug- gested if grass foliage is dense. Poast may also be used for control of johnsongrass (see section on specific weed problems). Do not tank mix Poast with postemergence broadleaf herbicides as grass control will be reduced. Fusllade (fluazif op-butyl) is a selective postemergence herbicide for grass control in soybeans. It was labeled for experimental use in 1982 and may be given full registration in 1983. Fusilade is used at the rate of V2 pint per acre on annual grasses up to 10 inches tall and at Vi pint per acre on volunteer corn up to 36 inches tall. Fusilade will also control johnsongrass (see section on specific weed problems). Oil concentrate should be used at the rate of 1 to 2 pints per acre for ground application and 1 gallon per 100 gallons of water for aerial applica- tion. 12 \^star (mefluidide) may be used for postemergence control of johnsongrass in soybeans south of Highway 1-70 in Illinois. Vistar 2S is used at the rate of 1 pint per acre after the second trifoliate stage of soybeans, and when johnsongrass is less than 15 inches tall. A second application may be necessary 3 to 4 weeks after the first application but no later than 60 days prior to harvest. A nonionic surfactant should be used at the rate of 1 to 2 pints per 100 gallons of spray solution. Johnsongrass is not immediately killed by Vistar, and usually about 10 days will elapse before the leaves turn brown. Maximum results will be seen in about 3 weeks. Soybeans may also show some injury from Vistar, as indi- cated by leaf crinkling or slight growth suppression. Roundup (glyphosate) can be applied through several types of selective applicators — recirculating sprayers, wipers, or rope wicks. This application is particularly useful for control of volunteer com, shattercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be a minimum of 6 inches above the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soy- beans. For calibration of equipment, refer to Round- up label. For recirculating sprayers and wipers, use the rates given on the label. For rope-wick applicators, mix 1 gallon of Roundup in 2 gallons of water. Basat-Directed Postemergence Herbicides Several herbicides have been approved for directed application to the bases of soybean plants for control of late-emerging weeds. The soybeans must be at least 8 inches tall and weeds less than 2 to 4 inches tall. Nozzles must be mounted in a fixed position and accurately adjusted to spray only the lower one-third to one-fourth of the soybean plant. Precise positioning of the spray is essential to prevent serious soybean injury. Special equip- ment such as oiling shoes or gauge wheels is usually specified. Read the label for correct rates and equipment and for precautions. Some of the herbicides cleared for basal-directed sprays are : Lorox (linuron) alone or plus 2,4-DB or Premerge Sencor (metribuzin) alone or plus 2,4-DB Lexone (metribuzin) Butoxone SB or Butyrac 200 (2,4-DB) Paraquat Premerge Goal Most of these herbicides call for application before bloom or the midbloom stage of soybeans. Some of these treatments can be applied a second time. Basal-directed sprays are not very popular in Illinois because of the special equipment and degree of precision required for application. In Illinois the major weeds in soybeans usually begin growing at the same time and often at about the same rate as the soybeans. Thus it is often difficult to establish a suitable difference in height between the soybeans and weeds unless an early herbicide treatment has been used. If the early treatment is effec- tive, a later directed treatment may not be needed. Paraquat Harvest Aid Paraquat and Gramoxone are registered for drying weeds in soybeans just before harvest. For indeterminate varieties (most Illinois varieties), apply when 65 percent of the seed pods have reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when at least one-half of the leaves have dropped and the rest of the leaves are turning yellow. The rate is V2 to 1 pint of Paraquat or Gramoxone per acre. The higher rate is for cocklebur. The total spray volume per acre is 2 to 5 gallons for aerial application or 20 to 40 gallons for ground application. Add 1 quart of nonionic surfactant per 100 gallons of spray. Do not pasture livestock within 15 days of treatment, and remove livestock from treated fields at least 30 days before slaughter. Herbicides for Sorghum Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Ap- plication may be made preemergence or postemergence. Plant seed at least 1 inch deep. Do not use preplant or preemergence on soils with less than 1 percent organic matter. Incorporated treatments may show injury if rain- fall occurs prior to or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemer- gence is 2 to 3 pounds of atrazine SOW per acre. The postemergence rate is 2V2 to 3M pounds SOW per acre. Rotational crop recommendations and weed control are the same as for atrazine used in corn. Failure to control fall panicum has been a major problem. Ramrod (propachlor) may be used alone or in com- bination with atrazine, Milogard, Bladex, or Modown for sorghum. Ramrod will improve grass control, but rates must not be skimpy, especially on soils relatively low in organic matter. For specific rates, consult the label. Dual (metolachlor) or Dual plus atrazine (or Bleep) can be used on sorghum seed that has had the Concep- seed treatment. These herbicides will improve grass con- trol more than atrazine applied alone. Milogard (propazine) has better sorghum tolerance than atrazine, but grass control is not as good. Only com or sorghum may be planted in rotation within 12 months after treatment. 2,4-D may be applied postemergence for broadleaf control in 4- to 12-inch tall sorghum. Use drop nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in corn (see section on corn herbicides). Banvel can be applied postemergence until sorghum is 15 inches tall or 25 days after emergence. The rate is V2 pint per acre. Do not graze or feed treated forage or 13 silage prior to the mature grain stage. Sorghum may be injured by Banvel. Specific Weed Problems Yellow Nutsedge YeIIo\v nutsedge is a perennial sedge with a triangular stem. It reproduces mainly by tubers. Regardless of the soil depth at which the tuber germinates, a basal bulb develops 1 to 2 inches under the soil surface. A complex system of rhizomes (underground stems) and tubers de- velops from this basal bulb. Yellow nutsedge tubers begin sprouting about May 1 in central Illinois. For the most effective control, soil-applied herbicides should be incor- p>orated into the same soil layer in which this basal bulb is developing. For soybeans, a delay in planting until late May allows time for two or three tillage operations to destroy many nutsedge sprouts. Tillage helps deplete food reserves in nutsedge tubers. Row cultivation is helpful. Preplant ap- plications of Lasso, Dual, or Vernan will also help. Lasso (alachlor) applied preplant incorporated at 3 to 4 quarts per acre (','2 quart more than for surface- applied rates) often gives good control of nutsedge. Dual (metolachlor) can be applied at 2 to 3 pints of 8E per acre to control nutsedge. Preplant treatment is preferred to treatment at the preemergence stage. \'emam 7E (vernolate) applied preplant at 31: pints per acre is also effective against yellow nutsedge. Imme- diate incorporation is necessary with Vemam. Basagran (bentazon) is a postemergence treatment that can also help control nutsedge in soybeans. One quart per acre can be applied when nutsedge is 6 to 8 inches tall. A split application (two treatments) of Basa- gran has also been registered. Addition of a crop-oil con- centrate to Basagran may improve performance. For corn, preplant tillage before nutsedge sprouts is of httle help in control. Timely cultivation gives some con- trol, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane (EPTC) or Sutan-f (butylate) at iVi to IVs pints per acre are effective for control of yellow nutsedge in corn. They must be incorporated immediately. Lasso or Dual applied in corn as for soybeans can also be quite effective. The combinations of Lasso, Dual, Sutan + , or Eradi- cane incorporated with atrazine may give better control of nutsedge while also controlling broadleaf weeds. Atrazine or Bladex (cyanazine) is used as a postemer- gence spray to control emerged yellow nutsedge when it is small. Split applications of atrazine plus oil have been more effective than single applications. Basagran can be used in com in a manner similar to that for soy- beans. Lorox (linuron) directed postemergence spray has also given some control. Johnsongrass Johnsongrass can reproduce both from seeds and bv rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the johnson- grass head begins to appear. Mowing, grazing, or culti- vating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, making them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or suppressed using certain herbicides in various cropping programs. Several preplant-incorporated herbicides can provide control of johnsongrass seedlings in soybeans or com (see the table at the end of this publication) . Treflan (trifluralin), Prowl (pendimethalin), or Basa- lin (fluchloralin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnson- grass. They are used at l'/2 to 2 times the normal rate each year for 2 years, and then either at the normal rate, or another suitable herbicide is used the third year before resuming a regular cropping sequence. Thorough pre- plant tillage and incorporation are necessary for satis- factory' control. Be certain not to plant such crops as corn or sorghum following application of these herbicides at the higher rates. Fusilade (fluazif op-butyl) can control johnsongrass in soybeans. Apply V2 pint per acre when the weed is at most 36 inches tall. A split application of Vi pint plus V2 pint applied about 3 weeks apart may give better control. Feast (sethoxydim) can control johnsongrass in soy- beans. Apply IV2 pints plus 1 quart crop oil concentrate per acre \vhen the johnsongrass is 24 inches tall. A second application of 1 pint per acre may be required. Eradicane (EPTC) or Sutan+ (butylate) will sup- press rhizome johnsongrass in com when used at a rate of 7V'3 pints per acre as a preplant-incorporated treat- ment. However, this increase in rate also increases the risk of com injury. Dalapon can be used to treat emerged johnsongrass before planting com or soybeans. Apply 5 to 7 pounds per acre after the grass is 8 to 12 inches tall. Plow or disk after 3 days and then delay planting corn or soybeans at least 1 week. See the label for specific intervals. Dalapon can also be used to control johnsongrass after wheat that is not double cropped or undersown with a legume. A combination of mowing, timely dalapon ap- plication, and tillage has provided quite effective control. Roundup (glj'phosate) can be used as a spot treat- ment to control johnsongrass in corn, soybeans, or sor- ghum. Apply 2 to 3 quarts when johnsongrass has reached the boot to head stage and is acti\-ely growing. Use of Roundup in wick or recovery-type sprayers is effective for control of johnsongrass in soybeans. (See section on postemergence herbicides for soybeans.) Roundup may be applied in small grain stubble when i 14 johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass Quackgrass is a perennial grass with shallow rhizomes. Most preemergence herbicides will not control it. Atrazine is quite effective when used as a split appli- cation in corn. Apply 2'/2 pounds of atrazine SOW per acre in the fall or spring and plow 1 to 3 weeks later. Another 2'/2 pounds per acre should be applied as a pre- plant or preemergence treatment. Postemergence appli- cation is usually less effective. A single treatment with 3% to 5 pounds per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. If more than 3 pounds of atrazine is applied per acre, plant no crops other than corn or sorghum the next year. Eradlcane (EPTC) can be used to suppress quack- grass in com where more flexibility in cropping sequence is desired. A rate of 4% pints per acre of Eradicane 6.7E can be used on light infestations, while 7'/3 pints per acre is suggested for heavier infestations. There is some risk of corn injury, especially at the higher rate. A tank mix with atrazine should improve control. Fusilade (fluazif op-butyl) is registered and will be labeled for quackgrass control in soybeans at Vi pint per acre. Apply when quackgrass is 6 to 8 inches high. Poast (sethoxydim) can be applied in soybeans at the rate of 2'/2 pints plus 1 quart of crop oil concentrate per acre when quackgrass is 8 to 12 inches tall. A second application of l'/2 pints per acre or a cultivation may be required for season-long control. Dalapon can be applied to quackgrass 4 to 6 inches tall in the spring at a rate of 8 pounds per acre. Plow after 4 days and delay planting com for 4 to 5 weeks. Up to 15 pounds of dalapon per acre may be used in the fall. Roundup (glyphosate) can be used for controlling quackgrass before planting either com or soybeans. Apply 2 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). Delay tillage for 3 or more days after application. Canada Thistle Canada thistle is a perennial weed that has large food reserves in its root system. There are several varieties of Canada thistle. They differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in corn. Banvel (dicamba) often is a little more effective than 2,4-D and may be used alone or in combination with 2,4-D, Banvel can be used as an after-harvest treatment in wheat, corn, or soybean fields at 2 quarts per acre. Fall treatments should be apphed before killing frosts. For best results thistles should be fully emerged and actively growing. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in com. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Can- ada thistle in soybeans or corn when the thistles are 8 to 12 inches tall. Apply % to 1 quart per acre in a single application, or for better control make two applications of Vi to 1 quart per acre each, 7 to 10 days apart. Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow 3 or more days after application before tillage. Amitrole or Amitrole-T effectively controls Canada thistle, but can be used only in noncrop areas. Tordon (picloram) gives good control of Canada thistle, but soybeans and most other broadleaf plants are extremely sensitive to it. Use only on noncropland. Black Nightshade Black nightshade is an annual weed that has become an increasing problem for Illinois soybean growers. The principal problem is caused by the berries, which are about the same size as soybeans at harvest. They contain a sticky juice that can gum up a combine. Black nightshade does not present much of a problem in com but should be controlled nonetheless to help re- duce production of the weed's seed. Herbicides such as atrazine, Bladex, Banvel, Lasso, and Dual are helpful for controlling this weed in corn. It can be helpful to plant suspect fields to com rather than soybeans. If soybeans must be planted, plant suspect fields last. This makes the full strength of the herbicide last longer to help control the midseason flush. Preemer- gence applications usually maintain control longer than those that are preplant incorporated. For control in soybeans, Lasso, Dual, or Amiben at full rates or a combination of Amiben or Lorox with Lasso or Dual is helpful. Suspect fields should be monitored and a postemergence application of Blazer considered. Harvest-aid sprays generally do not solve the problem because they do not make the berries fall before the soy- beans are harvested. Additional Information Not all herbicides and herbicide combinations avail- able are mentioned in this publication. Some are rela- tively new and are still being tested. Some are not con- sidered to be very well adapted to Illinois or are not used very extensively. For further information on field crop weed control, consult your county Extension adviser or write to the Department of Agronomy, N-305 Turner Hall, 1102 S. Goodwin Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. 15 Relative Effectiveness of Herbicides on Major Weeds This chart gives a general comparative rating. Under unfavorable conditions, some herbicides rated good or fair may give erratic or poor re- sults. Under very favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when se- lecting herbicides. Rate of herbicide used also will influence results. G = good, F •= fair or variable, and P = poor. Grasses Broadleaf Weeds u u o bo •a it a E a 5 bo XI n Ut U B 3 'S a (3 M u bo 5 OJ O •— > V a e s b. u C "o > o bo M 3 C o bo c 3 O < IS o o U -a C o .1 f2 3 s h-1 3 13 t bo bo c o o u u I a Pi 4^ J bb 1 1 a B > SOYBEANS Preplant Treflan, Prowl, Basalin F-G G G G G G G F P F-P P p G P G P P P-F p Sencor, Lexone + dinitroaniline F G G G G G G F P F F F-G G P G G F G F-G Vernam F G G G G G G F-P F F-P P P F P G P P P F Preplant or Preemergenee Amiben F-G G F-G F-G F-G F F P P P P P-F G F-G G F-G F F-G F Lasso, Dual G G G G G P-F P-F P F-G P P P F F-G G P-F P P-F P Lasso or Dual + Sencor or Lexone F G G G G P P P F P F F-G G F G F F G F-G Lasso or Dual + Lorox' F G G G G P P P P-F P F F G F-G G G F G F-G Lorox' F F F F F P P P P P F F G F G G F G F-G Modovm, Goal F F F F F P P P P F-P P F G F G F P G F Sencor, Lexone* F F F F F P P P P-F P F F-G G P G G F G F-G Postemergence Basagran F-G P P P P P P P F P-F G G F-P P P F F G F-G Blazer F P-F P P-F P P P P P F-G F G F-P F-G G F F G P Dyanap F P P P P P P P P F-G G G F-G P-F F-G F F F P 2,4-DB P-F P P P P P P P P F-G G P-F F P F F F P P Hoelon G G G F-P F P P G P P P P P P P P P P P Poast, Fusilade G G G G G G G G P P P P P P P P P P P CORN Preplant Sutan + , Eradicane F-G G G G G F-G F-G F-G P P P P-F F G P P P F Sutan+ or Eradicane + atrazine, Bladex F-G G G G G F-G F-G F-G F-G F-G G G G G G F G F-G Princep + atrazine G F-G F-G F F P P-F P F-G F-G G G G G G G G F Preplant or Preemergenee Atrazine G F-G F P P P P F G F-G G G G G G G G F-G Banvel + Lasso or Dual F-G G G G G P P F P-F F F-G G G G G F G F Bladex F-G F-G F-G F-G G P P P F F-G G G G F G F-G G F Bladex + atrazine F-G F-G F F F-G P P P F-G F-G G G G G G F-G G F-G Lasso, Dual F-G G G G G P-F P-F F-G P P P F F G P-F P P-F P Lasso or Dual + atrazine or Bladex F-G G G G G P P F-G F-G F G G G G G F G F Prowl + atrazine or Bladex' F G G G G F F P F-G F G G G G G F G F-G Ramrod + atrazine or Bladex' G G G F-G F P P P-F F-G F G G G G G F G F Ramrod G G F F-G F P P P-F P P P F P G P P P P Postemergence Atrazine + oil F-G F-G G P P P P F G G G G G G G F G G Banvel F-G P P P P P P P G G G G G G G G G F Basagran G P P P P P P F P-F G G F-P P P F F G F-G Bladex F-G G G F F-G P P F F F-G G F G F-G G F G F-G 2,4-D F P P P P P P P G G F G F G G G P-F F-G Preemergenee only 15M— 10-82— 55147— twk "A Ha,r,C '5' 1984 Row Crop Weed Control Guide Precautions 1 Cultural and Mechanical Control 1 Herbicide Incorporation 2 Chemical Weed Control 2 Names of Some Herbicides 3 Herbicide Combinations 3 Herbicide Rates 3 Postemergence Herbicide Principles 4 Conservation Tillage and Weed Control 4 No-Till and Double-Crop 4 Herbicides for Com 5 Herbicides for Soybeans 9 Herbicides for Sorghum 13 Specific Weed Problems 13 Additional Information 15 This guide is based on the results of research con- ducted by the University of Illinois Agricultural Experi- ment Station, other experiment stations, and the U.S. Department of Agriculture. Consideration has been given to the soils, crops, and weed problems of Illinois. Rainfall, soil type, method of application, and formula- tion influence herbicide effectiveness. Under certain con- ditions some herbicides may damage crops to which they are applied. In some cases, herbicide residues in the soil may damage crops grown later. • Check label for proper method of container disposal. Triple rinse, puncture, and haul metal containers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or bum them in an approved manner. • Return unused herbicides to a safe storage place promptly. Store them in original containers, away from unauthorized persons, particularly children. • Since manufacturers' formulations and labels are -SiMii^tifees changed and government regulations modi- - i\QH^^ hed, always refer to the most recent product label. This guide has been developed to help you use herbi- o ;\ cklfes As effectively and safely as possible. However, since ,^,, , . , , . . , -,111 • Dt-^ '' no guide can remove all the risk involved, the University When selectmg a herbicide, consider both the risk in- ^^ imnQi^and its employees assume no responsibility for yolved m using the herbicide and the yield osses caused ^^^ C^|igV\ising herbicides, even if they have been used by weeds. You can reduce risks by taking these R5^^6egp,t^^«^?^ing to the suggestions, recommendations, or direc- tions of the manufacturer or any governmental agency. Precautions by tions • Apply herbicides only to those crops for which use has been approved. • Clean tanks thoroughly when changing from com to soybeans, especially when using a postemergence her- bicide. • Use recommended rates. Applying too much herbi- cide is costly and in addition may damage crops and cause illegal residues. Using too little herbicide can result in poor weed control. • Apply herbicides only at times specified on the label. Observe the recommended intervals between treatment and pasturing or harvesting of crops. • Wear goggles, rubber gloves, and other protective clothing as suggested by the label. • Guard against drift injury to nearby susceptible plants, such as soybeans, grapes, and tomatoes. Mist or vapors from 2,4-D, MCPA, and dicamba sprays may drift several hundred yards. When possible, operate sprayers at low pressure with tips that deliver large droplets. Spray only on calm days or make sure wind is not moving toward susceptible crop plants and ornamentals. • Apply herbicides only when all animals and persons not directly involved in the application have been re- moved from the area. Avoid unnecessary exposure. Cultural and Mechanical Control Most weed control programs combine good cultural practices, mechanical weed control, and herbicide appli- cations. Good cultural practices to aid weed control in- clude adequate seedbed preparation, adequate fertiliza- tion, crop rotation, seeding on the proper date, use of the optimum row width, and seeding at the rate for optimum stands. Planting in relatively warm soils helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both com and soybeans. If weed control is adequate during that period, com and soybeans will usually compete quite well with most of the weeds that begin growth later. Narrow rows will shade the centers faster and help the crop compete better with the weeds. However, if herbi- cides alone cannot give adequate weed control, then keep rows wide enough to allow cultivation. Some of the newer herbicides are improving the chances of adequate control without cultivation. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Use the rotary hoe after weed seeds have germinated but before most have emerged. Operate it at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small weeds. Cultivate shallow to prevent injury to crop roots. Avoid excessive ridging; it may hinder harvesting and encourage erosion. Herbicides can pro\'ide a convenient and economical means of early weed control by allowing delayed and faster cultivation. Furthermorej unless the soil is crusted, it is usually not necessary to cultivate at all when herbi- cides are controlling weeds adequately. Herbicide Incorporation Soil-applied herbicides are incorporated to minimize surface loss, reduce dependence upon rainfall, and pro- vide appropriate placement of the herbicide. Sutan+ and Eradicane are incorporated soon after application to minimize surface loss from volatilization. Dinitroaniline herbicides such as Treflan and Basalin are incorporated within a few hours to minimize loss due to photode- composition and volatilization. Triazine herbicides such as atrazine and Bladex and acetanilide herbicides such as Lasso and Dual may be incorporated to minimize de- pendence upon timely rainfall, but time of incorporation for them is less critical since they are not lost so quickly from the soil surface. Incorporation should place tlie herbicide uniformly in the top 1 to 2 soil inches of soil for best control of small- seeded annual \veeds that germinate from shallow depths. Slightly deeper placement may improve the control of certain weeds from deep-germinating seed under rela- tively dry conditions. The field cultivator and tandem disk place most of the herbicide one-half of the depth of operation. Thus for most herbicides the suggested depth of operation is 3 to 4 inches. Thorough incorporation with ground-drive implements may require two passes. Single-pass incorporation tends to result in streaked weed control, especially in wet soils. Single-pass incorporation may be adequate with some equipment, especially if rotan,' hoeing and cultivation are used to improve ^\"eed control. If the herbicide is suffi- ciently covered to prevent surface loss with the first pass, the second pass can be delayed until immediately before planting. The depth and thoroughness of incorporation depend upon the type of equipment, depth and speed of opera- tion, soil texture, and soil moisture. Field cultivators and tandem disks are common implements used for incorpo- ration. However, disk-chisels and other combination tools are being used in some areas. Field Cuhivafors Field cultivators are frequently used for herbicide in- corporation. They should have three or more rows of shanks with an effective shank spacing of no more than 8 to 9 inches (a spacing of 24 to 27 inches on each of three rows). The shanks can be equipped with points or sweeps. Sweeps usually give better incorporation, espe- cially when soil conditions are a little too wet or dry for optimal soil flow and mixing. Sweeps for "C" shank culti- vators should be at least as wide as the effective shank spacing. The recommended operating depth for the field culti- vator is 3 to 4 inches. It is usually necessary to operate only deep enough to remove tractor-tire depressions. The ground speed should be at least 6 mph. The field culti- vator must be operated in a level position so that the back shanks are not operating in untreated soil, which \vould result in streaked weed control. Two passes are recom- mended to obtain uniform weed control. If single-pass incorporation is preferred, the use of wider sweeps or narrower spacing ^\ith a 3- to 5 -bar harrow or rolling baskets pulled behind will increase the probabiUty of obtaining adequate weed control. Tandem Disks Tandem disk harrows invert the soil and usually place the herbicide deeper in the soil than most other incorpo- ration tools. Tandem disks used for herbicide incorpora- tion should have disk blade diameters of 22 inches or less and blade spacings of 7 to 9 inches. Larger disks are con- sidered primary tillage tools and should not be used for incorporating herbicides. Spherical disk blades give better herbicide mixing than conical disk blades. Tandem disks usually place most of the herbicide in the top 50 to 60 percent of the depth of operation. For most herbicides, the suggested operating depth is from 3 to 4 inches. Two passes are recommended to obtain uni- form mixing with a double disk. A leveling device (har- row or rolling baskets) should be used behind the disk to obtain proper mixing. Recommended ground speeds are usually between 4 and 6 mph. The speed should be suf- ficient to move the soil the full width of the blade spac- ing. Lower speeds can result in herbicide streaking. Combination Tools Several new tillage tools combine disk gangs, field cultivator shanks, and le\'eling devices. Many of these combination tools can handle large amounts of surface residue without clogging and yet leave considerable crop residue on the soil surface for erosion control. Results indicate that these combination tools may provide more uniform one-pass incorporation than does a disk or field cultivator, but one pass \vith them is no better than two passes with the disk or field cultivator. Chemical Weed Contro! Plan your weed-control program to fit your soils, crops, weed problems, and farming operations. Herbicide performance depends on the weather and on \\ise selec- tion and application. Your decisions on herbicide use should be based on the nature and seriousness of your weed problems. The herbicide selectivity table at the end of this guide indicates the susceptibility of our most common weed species to herbicides. Com or soybeans may occasionally be injured by some of the herbicides registered for use on them. Apply the herbicide at the time specified on the label and at the correct rate in order to reduce crop injury (see section entitled "Herbicide Rates"). Crop tolerance ratings for various herbicides are also given in the table at the end of this guide. Corn or soybeans under stress from soil crusting, depth of planting, or adverse weather are prone to herbicide injury. Once injured by a herbicide, plants are prone to disease. Crop planting intentions for the next season must also be considered. Where atrazine or simazine are used, you should not plant spring-seeded small grains, small-seeded legumes and grasses, or vegetables the following year. Be sure that the application of Treflan or similar herbicides for soybeans is uniform and sufficiently early to reduce the risk of injury to wheat or corn following soybeans. Refer to the herbicide label for cropping sequence infor- mation. Names of Some Herbicides Trade Common (generic) AAtrex, Atrazine atrazine Alanap naptalam Amiben chloramben Banvel dicamba Basagran bentazon Basalin fluchloralin Bleep metolachlor + atrazine Bladex cyanazine Blazer acifluorfen Bronco alachlor + glyphosate Buctril, Brominal bromoxynil Butoxone, Butyrac 2,4-DB Dowpon M dalapon Dual metolachlor Dyanap naptalam plus dinoseb Eradicane Extra EPTC Evik ametryn Furloe Chloro IPC chlorpropham Fusilade fluazif op-butyl Hoelon diclof op-methyl Laddok bentazon + atrazine Lasso alachlor Lorox linuron Milogard propazine Modown bifenox Paraquat Plus, Gramoxone paraquat Poast sethoxydim Princep, Simazine simazine Prowl pendimethalin Ramrod propachlor Rescue naptalam plus 2,4-DB Roundup glyphosate Sencor, Lexone metribuzin (several) 2,4-D Surflan oryzalin Sutan+, Genate Plus butylate Sutazine butylate plus atrazine Treflan trifluralin Vernam vemolate Vistar mefluidide Some herbicides have different formulations and con- centrations under the same trade name. No endorsement of any trade name is implied, nor is discrimination against similar products intended. Herbicide Combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package mix," while others are tank mixed. Tank mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifiable concentrate (EC) formulations with wettable powder (WP), water dispersible liquid (WDL), or water dis- persible granule (WDG) formulations. These problems can sometimes be prevented by using proper mixing pro- cedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides that are sus- pended. If using liquid fertilizers, check compatibility in a small lot before mixing a tankful. The addition of compatibility agents may be necessary. Wettable pow- ders, WDGs, or WDLs should be added to the tank be- fore ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to prevent accumulation of ma- terial on the sides and the bottom of the tank. The user can apply two treatments of the same herbi- cide (split application), or he can use two different ones, provided such uses are registered. Applying two herbi- cides at different times is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant application might be followed by a preemergence application, or a soil-applied treatment might be followed by a postemer- gence treatment. One herbicide may be broadcast while the other is banded or directed. Herbicide Rates Herbicide rates vary according to the time of applica- tion, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence application than for pre- plant incorporated application. Postemergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary depending on the size and species of the weeds and on whether an adjuvant is specified. Rates for combinations are usually lower than for herbicides used alone. The rates for soil-applied herbicides usually vary de- pending on the texture of the soil and the amount of organic matter it contains. For instance, light-colored, medium-textured soils ^\•ith little organic matter require relatively lower rates of most herbicides than do the dark- colored, fine-textured soils with medium to high organic matter. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemer- gence rather than soil-applied herbicide," depending on the herbicide and its adaptation and on crop tolerance. The rates given in this publication are, unless other- wise specified, broadcast rates for the amount of formu- lated product. If you plan to band or direct herbicides, adjust the amount per crop acre according to the per- centage of the area actually treated. Many herbicides have several formulations with diflferent concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formulations. Postemergence Herbicide Principles Postemergence herbicides applied to growing weeds generally have foliar rather than soil action; however, some may have both. The rates and timing of applica- tions are based on weed size and climatic conditions. Weeds can usually be controlled with a lower application rate when they are small and tender. Larger weeds often require a higher herbicide rate or the addition of a spray additive, especially if the weeds have developed under drouth conditions. Herbicide penetration and action are usually greater when the temperature and relative hu- midity are high. Rainfall occurring too soon after appli- cation (1 to 8 hours, depending on the herbicide) can cause poor weed control. Translocated (hormone) herbicides can be effective with partial foliar coverage, whereas contact herbicides require complete coverage. Foliar coverage increases as water volume and spray pressure are increased. Spray nozzles that produce small droplets also improve cover- age. For contact herbicides, 20 to 40 gallons of water per acre are often recommended for ground application and a minimum of 5 gallons per acre for aerial application. Spray pressures of 30 to 50 psi are often suggested with flat-fan or hollow-cone nozzles to produce small droplets and improve canopy penetration. Such small droplets are quite subject to drift. The use of a surfactant or crop oil concentrate may be recommended to improve spray coverage. These spray additives will usually improve weed control but may increase crop injury. Spray additives may be needed only under drouth conditions or on larger weeds. Crop size limitations may be specified on the label to minimize crop injury and maximize weed control. If weeds are smaller than the crop, basal-directed sprays may minimize crop injury because they place more herbicide on the weeds than on the crop. If the weeds are taller than the crop, rope-wick applicators or recirculating sprayers can be used to place the herbicides on the top of the weeds and minimize contact with the crop. Follow the label directions and precautions for each herbicide. Conservation Tillage and Weed Control Conser\'ation tillage refers to tillage methods that provide efficient crop production along with adequate control of soil erosion caused by ^vind and water. Erosion control is obtained by protecting the soil surface with plant residue. The amount of tillage is less than in con- \-entional moldboard plowing. Chisel plowing, disking, or no tillage is used ; several other systems are also available. With these reduced tillage systems, weed control is often a problem because more weeds have to be con- trolled with herbicides. Furthermore, the herbicides can- not be incorporated without covering much of the resi- due that is necessary for effective erosion control. The early application of preplant, preemergence, or post- emergence herbicides is an alternative to incorporation. Early preplant herbicides are surface applied 2 to 4 weeks before planting and before weeds emerge. Early application may eliminate the need for a contact herbi- cide at planting. However, early preplant application may require additional herbicides (preemergence or post- emergence) or cultivation for satisfactory weed control. Compared with preplant incorporated herbicides, preemergence herbicides require less tillage, but their per- formance is more dependent upon timely rainfall. How- ever, they have performed better than herbicides that are poorly incorporated. With conservation tillage, a higher application rate of surface applied herbicides may be re- quired for satisfactory weed control, especially in fields with considerable weed infestation. Do not, however, use a higher rate than stated on the label instructions. Also, use great care when selecting herbicides and choosing application rates. The use of effective postemergence herbicides, which depend upon foliar rather than soil action, may be a logical choice with some conservation tillage systems. No-Till and Double-Crop Com and soybeans are sometimes produced without seedbed preparation, either in last year's crop residue (no-till) or as a second crop after small grain harvest or forage removal (double-crop). The no- till concept of planting has greatly improved the probability of success of double-cropping by conserving soil, soil moisture, and time. No-till herbicides must control both vegetation existing at planting and seedling weeds that germinate after planting. Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop, or weeds that emerge in the previous year's crop stubble before planting. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor, especially if herbicides are applied before regrowth. Labeled applications of 2,4-D, Banvel, or pos- sibly Roundup can improve control of broadleaf peren- nials when used for registered crops, such as corn or sorghum. Several precautions should be observed in no-till crop- ping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact from herbicide sprays. (Several herbicide labels give planting depths necessary to avoid possible injury.) Pre- emergence applications of the herbicide treatment may give better weed control than preplant applications since the planting process may expose untreated soil contain- ing viable weed seed. The total reliance on chemical weed control and large amounts of crop residue present under no-till cropping systems may require that the higher labeled herbicide rates be used to obtain accept- able weed control. Early preplant application of pre- emergence herbicides may reduce the need for a foliar knockdown herbicide. Postemergence herbicides may be needed in no-till soybeans. Paraquat Plus or Gramoxone (1 or 2 pints per acre) plus a nonionic surfactant at V2 pint per 100 gallons of diluted spray is generally used to "knock down" existing foliage before crop emergence. Smartweed, giant rag- weed, and fall panicum may not be controlled if they are over 10 to 12 inches high and if no rain occurs to "acti- vate" the residual herbicides. A minimum of 40 gallons or more of spray per acre is suggested to ensure adequate coverage of the foliage. Paraquat and Gramoxone are re- stricted-use pesticides. Roundup (3 to 8 pints per acre) should be considered as an alternative treatment for control of the foliage prior to crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can translocate to the roots to give better con- trol of perennials. Use 20 to 30 gallons of spray volume per acre. Bronco is a formulated mixture of glyphosate (Roundup) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Do not apply in liquid fertilizers. Roundup, paraquat, and Bronco are registered for use in combination with the preemergence herbicides indi- cated in Table 1. See the sections entitled "Herbicides for Corn" and "Herbicides for Soybeans" for more informa- tion on these products. Herbicides for Corn All herbicides mentioned in this section are registered for use on field corn and also on silage corn unless other- wise specified. See Table 2 for registered combinations. Herbicide suggestions for sweet corn and popcorn may be found in Circular 907, 1984 Weed Management Guide for Commercial Vegetable Growers. Growers pro- ducing hybrid seed corn should check with the contract- ing company or inbred producer about tolerance of the parent lines. Preplant Incorporation Preplant application should be made anytime during the 1 or 2 weeks before planting. Incorporation should distribute the herbicide uniformly in about the top 2 inches of soil. Do not apply herbicides too early or in- corporate them too deeply. Sutan+, Genate Plus (butylate), or Eradicane Extra (EPTC) contain crop safening agents. Crop injury is unlikely, but may occur when growing conditions are unfavorable or when certain hybrids are used. Eradicane Extra also contains an extender to lengthen weed control. These herbicides control annual grasses and can control or suppress shattercane and johnsongrass at higher rates. The rate for Sutan+ and Genate Plus is 4% to 7'/3 pints per acre. The rate for Eradicane Extra 6E is 2% to 4 quarts per acre. Use the higher rates for heavy infesta- tions of shattercane and yellow nutsedge and for johnson- grass. These herbicides can be applied within 2 weeks be- fore planting, but they should be incorporated into the soil soon after application. Sutan+ and Eradicane Extra can also be injected into the soil with anhydrous am- monia. Injection should be 4 to 5 inches deep with shanks spaced no wider tlian 8 to 10 inches. This type of appli- cation is affected by soil moisture and physical conditions of the soil. Refer to labels for more information. Table 1. — Registered No-Till Herbicide Combinations Combination Alone Dual Lasso Surflan Prowl Soybeans Lorox PB PR PR PR P Lexone PB PR PR PR P Sencor PB PR PR PR P Corn Atrazine PB PR PR — — Bladex PB P PR — — Princep B PR PR — — Atrazine -j- Bladex B — — — — Atrazine + Princep PBR PR PR — — Bicep PR — — — — Knockdown herbicides: P = Paraquat, Gramoxone (paraquat). R =: Roundup (glyphosate). B = Bronco = Roundup -j- Lasso. — = Not registered. Table 2. — Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Corn A^ ■ Di J Atrazine Atrazine Atrazine Bladex _p ui ■ i_ d • -f- Bladex + Princep PPI only Eradicane .... 1 1 1 — Genate Plus. . . 1 1 1 — Sutan+ Ill — PPI or Pre Used alone... 1,2,3 1,2,3 1,2,3 1,2 Dual 1,2,3 1,2 1,2 1,2 Lasso 1,2,3 1,2 1,2 — 1 = Preplant incorporated; 2 ;= preemergence; 3 = early postemergence. ^ =: Not registered. Sutan+, Genate Plus, or Eradicane can be tank mixed with atrazine or Bladex to improve broadleaf control. The atrazine rate is 2 to 3 pints of 4L, or equivalent amounts of SOW or 90WDG per acre. The Bladex rate is 3 to 4 pints of 4L or 2 to 2'/2 pounds of SOW per acre. Combinations with both atrazine and Bladex are also registered. Suta2lne+ 6L is a 4:1 mixture of Sutan+ and atra- zine. The application rate is 5V4 to IOV2 pints per acre. Preplant or Preemergence Herbicides Incorporation of the following herbicides is optional depending upon the weeds to be controlled and the likeh- hood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 weeks prior to planting, or soon after planting. Preplant incorporation of these herbicides controls weeds more eflFectively if rain- fall is hmited. Com tolerance of atrazine and simazine is good, but carryover to subsequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble and more persistent than atrazine. Thus, Princep is usually preplant incorporated, Princep plus atrazine can be used in 1:1 or 2: 1 combinations; the total rate is the same as for atrazine used alone. The rate for atrazine used alone is 2'/2 to 3% pounds of atrazine SOW, 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex 90WDG. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank mix combinations to improve broadleaf weed control. The rate for atrazine in combi- nations is V/2 to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to 1.8 pounds of AAtrex 90WDG. These rates may not provide adequate control of cockle- bur, morningglory, and velvetleaf but can reduce the risk of carryover. You can minimize carryover injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil to dilute the herbi- cide. The risk of carryover is greater the year after a cool, dry growing season and on soils with pH over 7.3. If you use atrazine at more than 3 pounds of active ingredient per acre or if you apply after June 10, plant only com or sorghum the next year. If you use atrazine in the spring and must replant, then plant only com or sorghum that year. Do not plant small grains, small seeded legumes, or vegetables in the fall or the following spring. Soybeans planted the year after an application of atrazine can also be affected from carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not persist in the soil as long as atrazine, but atrazine does have the advantage of better com tolerance. Bladex controls fall panicum and giant foxtail, but not broadleaf weeds, better than atra- zine. Bladex can be combined with atrazine at 3: 1, 2: 1, or 1 : 1 ratios of Bladex to atrazine (see label for rates) . The higher ratios will provide better grass control, while the 1 : 1 ratio will provide better broadleaf weed control. Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of corn injury. Bladex rates are P/2 to 6 pounds of SOW, VA to 43/4 quarts of 4L, or 8 to 27 pounds of 15G per acre. You can lessen the risk of corn injury by using reduced rates of Bladex in combinations. Bladex can be tank mixed with Lasso, Dual, Ramrod, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately before planting or after planting. Do not incorporate the Prowl or Ram- rod combinations. Three-way combinations of Bladex plus atrazine plus Lasso, Dual, Sutan+, or Eradicane are registered. The addition of a limited amount of atrazine should improve broadleaf control without increasing concern about carry- over. Lasso (alachlor) or Dual (metolachlor) can be ap- plied preplant incorporated or at the preemergence stage, Preplant incorporation will improve control of yellow nutsedge and can lessen dependence up>on rainfall. In- corporation should distribute the herbicide evenly in the top 2 inches of soil. Lasso and Dual control annual grasses and help con- trol yellow nutsedge. You can improve broadleaf weed control by using atrazine or Bladex in preplant combina- tions or by using atrazine, Bladex, or Banvel in preemer- gence combinations. Lasso can be applied anytime during the week before planting com and incorporated evenly into the top 2 inches of soil, or it can be used immediately after plant- ing. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate for the soil if you plan to incorporate Lasso. Dual can be applied anytime during the 2 weeks prior to planting corn and incorporated into the top 2 inches of soil, or it can be used immediately after planting. The rates are IV2 to 4 pints of Dual 8E or 6 to 16 pounds of Dual 25G per acre. Lasso or Dual plus atrazine can be applied preplant incorporated or after planting until corn is 5 inches tall and grass weeds are no larger than the two-leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is IV2 to 4 quarts of Lasso or VA to 2'/2 pints of Dual SE plus l'/2 to 2'/2 pounds of atrazine SOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds of AAtrex 90WDG. Dual is also cleared in a combina- tion with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atrazine. Bicep contains 2'/i pounds of metolachlor (Dual) and 2 pounds of atrazine per gallon. The rate is 2 to 4 quarts per acre. Lasso/atrazine (flowable) con- tains 2'/2 pounds of alachlor (Lasso) and IV^ pounds of atrazine per gallon. The rate is 3Vi to 4i4 quarts per acre. Dual or Lasso plus Bladex can be applied prior to planting and incorporated, or they can be applied during the preemergence stage after planting. The rate is 2 to 4 quarts of Lasso 4E or VA to 2V2 pints of Dual 8E plus 1 to 3M pounds of Bladex SOW or 1 to 3 quarts of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Preemergence Herbicides Banvel (dicamba) plus Lasso or Dual can be applied after planting until com is 3 inches high, but before grasses reach the two-leaf stage. The addition of Banvel improves control of broadleaf weeds without creating a risk of carryover injury. Banvel may injure com, espe- cially if recommended rates are exceeded, apphcations are not accurate and uniform, or if com is planted too shallow (less than li4 inches). Do not use this treatment on coarse-textured soUs or soils that are low in organic matter. The rate on soils with over 2V^ percent organic matter is 1 pint of Banvel plus 2V^ quarts of Lasso 4E, or 2 to 2y2 pints of Dual 8E per acre. Ramrod (propachlor) can be applied alone or with atrazine after the com is planted but before grasses reach the two-leaf stage. Granular formulations should be ap- plied before crop or weeds emerge. Ramrod performs well on soils with over 3 percent organic matter. Ramrod is irritating to the skin and eyes, so observe label precautions. Com tolerance is good. It controls annual grasses and pigweed. The rate is 4 to 6 quarts of Ramrod 4L or 20 to 30 pounds of 20G per acre. Prowl (pendim.etlialln) is registered only for use on corn after planting. Incorporation of Prowl may result in serious corn injury. Use only where it is possible to cover seed adequately with soil. Prowl can control annual grasses and pigweed and provides some control of smart- weed and velvedeaf. You can improve broadleaf weed control by combining Prowl with atrazine, Bladex, or Banvel. Prowl plus atrazine or Bladex may be applied in the early postemergence jieriod before grasses are in the two-leaf stage. These combinations may also help reduce the competition from wild proso millet. However, avoid postemergence application when com is under stress from cool, wet weather; otherwise, corn injury may result. The rate for such combinations is 1 to I'/a quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than 1 V2 percent organic matter. Sencor (metribuzin) is registered for preemergence use in corn in three-way combinations. The rate is V2 pound of Sencor 50W, V2 pint of Sencor 4L, or Vs pound of Sencor 75DF per acre {Vi pound of active ingredient per acre) . Sencor can be used at this rate in combination with Lasso or Dual plus atrazine or Bladex. Applying Sencor at this rate with the atrazine or Bladex may im- prove velvetleaf control but may also increase the poten- tial for com injury, especially with Bladex. Do not use this combination on coarse-textured soils, soils containing less than 2 percent organic matter, or soils with a pH of 7.0 or higher. Postemergence Herbicides Lasso, Dual, Ramrod, or Prowl plus atrazine, or Lasso or Dual plus Banvel can be used on corn between the preemergence and very early postemergence stages (see preemergence section). To get satisfactory control apply before grasses reach the two-leaf stage. For more infor- mation on postemergence principles see section entitled "Postemergence Herbicide Principles." Banvel plus atrazine can be applied up to 3 weeks after planting but before annual grasses are l'/2 inches high. The rate is V2 pint of Banvel plus V/2 to 2 pounds of atrazine SOW or 1 to 1.6 quarts of atrazine 4L. Atrazine can be applied before grass weeds are more than l'/2 inches high. Many annual broadleaf seedlings are more susceptible than grass weeds and may be treated until they are up to 4 inches tall. The addition of oil-surfactant mixes or surfactants has generally increased the effectiveness of jxystemergence atrazine. Crop-oil concentrates (80 percent oil and 20 percent surfactant) are used at the rate of 1 quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or about 1 pint per acre. Results with the oil-surfactant mixes have generally been better than those with surfactants. Applications of atrazine and oil sometimes damage com that has been under stress from prolonged cold, wet weather, or other factors. Do not use more than 2'/2 pounds of atrazine SOW or 2 quarts of atrazine 4L per acre if you mix with oil or oil concentrate. Do not add 2,4-D to the atrazine-oil treatment or severe injury may result. Mix the atrazine with water first and add the oil last. If atrazine is applied after June 10, do not plant any crop except com or sorghum the next year. Bladex (cyanazine) can be applied through the four- leaf stage of com growth but before weeds exceed l'/2 inches in height. The rate is l'/2 to 2i4 pounds of Bladex SOW per acre. Do not use Bladex 4L, as it contains oil and can increase the potential for injury. A mixture of Bladex plus atrazine is also registered for postemergence use. Injury to com may occur under cold, adverse grow- ing conditions. The injury may only be temporary yellow- ing but can be more severe. Under drouthy conditions certain agricultural surfactants or vegetable oils may be added to Bladex SOW to improve weed control. Do not use p>etroleum crop oils or apply with liquid fertilizers for postemergence application. Do not apply Bladex post- emergence to com under severe stress. Banvel or Banvel II (dicamba) can be applied from emergence until corn is 36 inches tall. Best results can be expected when using V2 to 1 pint of Banvel per acre as an overlay application when the com is in the spike to 5- inch stage. Application at this time offers up to 6 weeks of soil (residual) activity when the 1-pint rate is used. With this timing, crop tolerance is better than in pre- emergence treatments with Banvel. In addition, applica- tion rates can be higher than in the later postemergence treatment, and the likelihood of injury to nearby soy- beans is diminished. For applications of Banvel II on com from 5 to 36 inches tall the preferred rate is 1 pint per acre. Banvel is labeled as an overlay (sequential) treatment following Sutan+, Eradicane, Lasso, Dual, Ramrod, atrazine, Bladex, Princep, Roundup, or para- quat. For best results, use Banvel or Banvel II before June 20 with a spray volume of 20 gallons per acre and a spray pressure of no more than 20 psi to help reduce the risk to plants outside the target area. 2,4-D is an economical and effective treatment for controlling many broadleaf weeds in com. Use drop nozzles if com is more than 8 inches high to decrease the possibility of injury. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com. Do not apply 2,4-D to com from tasseling to dough stage. After the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-D's by air or high clearance equipment to control late-germinating broadleaf weeds that may interfere with harvest, or to suppress certain perennial weeds. The suggested broadcast rate of acid equivalent per acre is Ve to 14 pK)und of ester formulations or V2 pound of amine. This would be V3 to V2 pint of ester or 1 pint of amine for formulations with 4 pounds of 2,4-D acid equivalent per gallon. The ester forms of 2,4-D can vaporize and injure near- by susceptible plants. This vapor movement is more likely with high-volatile than with low-volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Com is often britde for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other symptoms of 2,4-D in- jury are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. High temperature and high humidity will increase the potential for 2,4-D injury, especially if com is growing rapidly. If it is necessary to spray under these conditions, it may be wise to reduce the rate by about 25 percent. Com hybrids differ in their sensitivity, and the proba- bility of injury increases when com is under stress. Buctril or Brominal (bromoxynil) may be used to control broadleaf weeds in field and silage com. It is im- portant to apply it when weeds are small and to use at least 20 gallons of water per acre for ground applications. Bromoxynil may cause some burning of corn leaves, but the effects are usually temporary. Buctril 2E (at the rate of 1 to l'/4 pints per acre) or Brominal 4E (at V2 to 1 pint) should be applied when corn is in the 2- to 4-leaf stage and before weeds are 4 to 6 inches tall. Use the higher rate on larger corn and weeds. Weeds controlled include lambsquarters, smart- weed, jimsonweed, common ragweed, and black night- shade. Pigweed and velvetleaf may require the higher rate if conditions are not ideal. Bromoxynil is less likely than 2,4-D to cause drift injury or com injury but offers less flexibility for time of application. Basagran (bentazon) is registered for postemergence use in com in a manner similar to that for soybeans (see soybean section) . Since com is quite tolerant of Basagran, the addition of a crop-oil concentrate is considered rela- tively safe. Basagran is also cleared at the rate of 1 to 1 V2 pints in combination with atrazine at 0.6 to 0.9 pound of SOW, 0.6 to 0.8 pound of 90WDG, or 1 to W2 pints of 4L per acre. Laddok is a formulated mixture of Basa- gran plus atrazine. The rate is 2.4 to 3.6 pints per acre. Oil concentrate is added at 1 quart per acre for control of annual broadleaf weeds only. The combination is more economical than Basagran alone and will reduce the carry-over potential from atrazine alone. Postemergence Soil-Applied Herbicides Prowl, Treflan, and Lasso can be applied to the soil as postemergence treatments. It may be necessary to use drop nozzles to avoid interference from com leaves and ensure uniform application to the soil. Prowl (pendimethalin) or Treflan (trifluralin) maybe applied to the soil and incorporated after field com is 4 (for Prowl) or 8 (for Treflan) inches high and up to the time of last cultivation. The field should be cultivated to control existing weeds and cover the roots at the base of the com before application. The herbicide should then be thoroughly and uniformly incorporated into the top inch of soil. Prowl may not need incorporation if irriga- tion or rainfall occurs soon after application. Prowl can be combined v^dth atrazine. These treatments may help to control late-emerging grasses such as shattercane, wild proso millet, or fall panicmn. Lasso (alachlor) may be used alone or with atrazine as a soil-applied post-emergence treatment in corn grown for seed to help control midseason annual grass weeds. Application should preferably be made after cultivation before weeds emerge and before the crop is 40 inches tall. Directed Postemergence Herbicides Directed sprays are sometimes needed for emergency situations, especially when grass weeds become too tall for control with cultivation. However, weeds are often too large for directed sprays to be effective. Directed sprays cannot be used on small com because a height difference between com and weeds is needed to keep the spray off the corn. Com leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox (linuron) may be applied as a directed spray after com is at least 15 inches high (free standing) but before weeds are 8 inches tall (preferably not more than 5 inches) . Lorox controls grass and broadleaf weeds. The broadcast rate is VA to 3 pounds of Lorox SOW or 1!4 to 3 pints of 4L per acre, depending on weed size and soil type. Add Surfactant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the corn as much as possible. Con- sider this an emergency treatment. Evik SOW (ametryn) is registered for directed use when com is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 2'/2 poiuxds Evik SOW per acre (broadcast) plus 2 quarts of surfactant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Herbicides for Soybeans Consider the kinds of weeds expected when you select a herbicide program for soybeans, especially when grow- ing soybeans in narrow rows. The herbicide selectivity table (see last page of this guide) lists herbicides and their relative weed control ratings for various weeds. Soybeans may be injured by some herbicides. However, they usually outgrow early injury with little or no effect on yield if stands have not been significantly reduced. Significant yield decreases can result when injury occurs during the bloom to f>od fill stages. Excessively shallow planting may increase the risk of injury from some herbi- cides. Accurate rate selection for soil type is especially essential for Lorox, Lexone, and Sencor. Do not apply Lorox, Lexone, Sencor, or Modown after soybeans have begun to emerge. FoUow label instructions as to rates, timing, incorporation, and restrictions. For registered combinations see Table 3. Preplant Herbicides Incorporation is required for Basalin, Treflan, and Vemam. Incorporation is optional for Amiben, Dual, Lasso, Modown, and Prowl when used alone and in some combinations. Dyanap, Lorox, and Surflan should not be incorporated. Incorporation can improve performance if rainfall is limited and may increase the effectiveness of Dual or Lasso in controlling nutsedge. Incorporation should distribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early applica- tion of the herbicide can cause significant reductions in weed control. For more information see section entitled "Herbicide Incorporation." Table 3. — Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Soybeans Amiben Sencor or Lexone Amiben + Sencor or Lexone Lorox PPI only Basalin 1 Treflan 1 PPI or Pre Dual 1,2 Lasso 1,2 Prowl 1,2 Surflan* 2 1 =: Preplant incorporated; 2 == — = Not registered. * Not for preplant incorporation. 1,2 1.2 1,2 2 1,2 1,2 1,2 2 preemergence. Dinitroanillne herbicides registered for weed control in soybeans are Basalin, Treflan, Prowl, and Surflan. Basalin and Treflan should be incorporated because of their low solubility and because of surface loss through vaporization and photodecomposition. Incorporation is optional with Prowl, but variable weed control and soy- bean injury may result from preemergence applications. Do not incorporate Surflan (see preemergence section). Incorporation should distribute the herbicide evenly in the top 2 to 3 inches of soil (see label for implement set- tings) . A deeper incorporation may improve shattercane and johnsongrass seedling control. Basalin, Prowl, or Treflan may be used for rhizome johnsongrass suppres- sion (see section on specific weed problems) . The dinitroaniHne herbicides control annual grasses, pigweed, and lambsquarters and may provide some con- trol of smartweed and annual momingglory. Prowl and Surflan may also partially control velvetleaf. However, acceptable control of most other broadleaf weeds requires combinations or sequential treatments with other herbi- cides. The dinitroanillne herbicides provide similar weed control, soybean tolerance, and persistence when recom- mended rates are used. Soybeans are sometimes injured by dinitroaniline herbi- cides. Plants that have been injured by incorporated treatments are stunted and develop swollen hypocotyls and shortened lateral roots. Such injuries are not usually serious. Plants injured by preemergence applications de- velop stem callouses at the soil surface, which can cause lodging and yield loss. Corn, sorghum, or small grains may be injured if they are grown subsequent to a soybean crop that has been treated with a dinitroaniline herbicide. The symptoms are poor germination and stunted, purple plants with poor root systems. To avoid carryover use no more than the recommended rates. Also, be sure that application and incorp>oration are uniform. The likelihood of carry- over increases with double cropping or late application and after a cool, dry season. Disking or chisel plowing provides for minimal dilution of herbicide residues. Treflan (trifluralin) can be applied alone anytime in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks prior to planting, while combinations with Amiben, Furloe, or Modown should be applied within a few days prior to planting. Incorpo- rate as soon as possible, but do not delay incorporation more than 24 hours (8 hours if soil is warm and moist). The rate is 1 to 2 pints of Treflan 4E or 10 to 20 pounds of Treflan 5G per acre. Basalin (fluchloralin) can be apphed anytime during the 8 weeks (alone) or 1 to 2 weeks (with Sencor or Lexone) prior to planting. Incorporate within 8 hours of application. The rate is 1 to 3 pints Basalin 4E per acre. Basalin can be combined with Sencor or Lexone to im- prove broadleaf weed control. Prowl (pendimethalin) can be applied within 60 days (alone) or 7 days (with Sencor or Lexone) prior to planting soybeans or applied after planting (see pre- emergence). Preplant treatments should be incorporated within 7 days of application. Mechanical incorporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, although rates for combinations widi Sencor or Lexone are lower than when the herbicide is used alone. Sencor or Lexone (metribuzin) plus Basalin, Prowl, or Treflan can be tank mixed and applied within 7 to 14 days of planting. Incorporate uniformly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is Vi to 1 pound of 50W, V2 to 1 pint of 4L or V3 to % pound of 75DF. L'se the normal rate, or slightly less, of the dinitroaniUne herbicide (see labels). The application of Sencor or Lexone can also be split, one part being incorporated and the other part applied before emergence. This method requires two applications but can give better broadleaf control and less injury than incorporating the same total amount of Sencor or Lexone in a single application. Amiben (chloramben) can be incorporated with Basa- lin, Treflan, or Pro\vl. The rate is 4 to 6 quarts of Amiben 25 per acre. Amiben can also be applied at the rate of 3 to 6 quarts per acre and incorporated with dinitroaniline plus Sencor or Lexone as a three-way combination. Vemam (vemolate) controls annual grasses and pig- weed. It sometimes provides fair control of annual morn- ingglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vemam can be applied within 10 days prior to planting and should be incorpo- rated immediately. The broadcast rate is 2'/3 to 3^2 pints of Vemam 7E or 20 to 30 pounds of Vemam lOG per acre. Vemam plus Treflan is labeled at the rate of 1 pint of Treflan plus 2'/3 to 3 pints of Vernam 7E per acre. The combination will reduce the risk of soybean injury, but it may also decrease control of velvetleaf and yellow nutsedge. Other labeled combinations inckide Vemam plus Amiben, Basalin, Lasso, or Furloe. Preplant or Preemergence Herbicides Lasso (alachlor) or Dual (metolachlor) can be ap- plied to soybeans preplant incorporated or during the preemergence stage. If applied prior to planting, apply Dual anytime within the 2 weeks prior to planting and Lasso within 1 week of planting. If rainfall is limited, incorporation can improve performance and increase yellow nutsedge control. Soybeans are quite tolerant of Lasso or Dual. The first to second trifoliate leaves often appear crinkled with a drawstring effect on the middle leaiflet, but these symptoms should not cause concern. Lasso or Dual controls annual grasses plus pigweed and can help control nutsedge and black nightshade. These herbicides can be combined with Lexone, Sencor, or Amiben (incorporated or preemergence) and with Lorox or Dyanap (preemergence only) to improve broadleaf weed control. The rate for Lasso is 2 to 4 quarts Lasso 4E or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is 114 to 3 pints per acre. Use the higher amount for the soil when incorporating or ^vhen black nightshade or yellow nutsedge are to be controlled. The rate for combi- nations is slightly less than that for the herbicide used alone (see labels) . Amiben (chloramben) can control annual grasses plus many broadleaf weeds in soybeans \s-hen used at the full rate. Do not expect control of cocklebur or annual mom- ingglor}'. Control of velvetleaf and jimsomveed is often erratic. Amiben occasionally injures soybeans, but dam- age does not usually affect yield. Injured plants may be stunted and have abnormal, shortened roots. If rain does not occur within 3 to 5 days of an Amiben preemergence application, you should rotary hoe. Amiben is best suited to soils with over 2.5 percent organic matter. Amiben can be applied alone or with Dual, Lasso, or Prowl as a preplant-incorporated or preemergence treat- ment. Amiben plus Sencor can also be mixed with Lasso, Dual, or Prowl as a preplant or preemergence treat- ment. Amiben can be applied as a preemergence treat- ment with Lorox, Lexone, or Sencor. The .\miben broadcast rate alone is 20 to 30 pwDunds of lOG, 4 to 6 quarts of 2S, or 2.4 to 3.6 pounds of 75DS per acre. The .Amiben rate in combinations is 3 to 6 quarts of 2S (1.8 to 3.6 pounds of 75DS) per acre. Use the higher rate where black nightshade, velvedeaf, or common ragweed is a problem weed. Sencor or Lexone (metribuzin) can be applied any- time during the 1 to 2 weeks prior to planting and in- corporated with Basalin, Dual, Lasso, Prowl, or Treflan. Incorporation should distribute the herbicide evenly in the top 2 inches of soil. It can be applied preemergence by itself or with Amiben, Dual, Lasso, Prowl, Surflan or Dyanap. Sencor or Lexone can control many annual broadleaf weeds except annual momingglory. Control of giant rag- weed, jimsonweed, and cocklebur is marginal at the re- duced rates necessary to minimize soybean injury. One S)Tnptom of soybean injury is yellowing (chlorosis) of the lower leaves at about the first trifoliate stage or later ; it may be f ollo\ved by browning of leaves and death of plants depending upon the severity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with pH over 7.5. Accurate, uni- form application and incorporation are essential. Adjust rates accurately according to soil conditions. Do not apply to very sandy soil. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is V2 to 1 pound of 50VV, V2 to 1 pint of 4L, or Vs to % pound of 75DF. You can use higher amounts as a split preplant and pre- emergence application. The higher amounts can improve broadleaf control but also increase the risk of soybean injury. Modown (bifenox) can control pigweed, lambsquar- ters, and smart^veed and provide some control of velvet- leaf. Modown 4F rates are 254 to 4 pints per acre. 10 Combinations with Treflan or Lasso will improve grass control. For preplant incorporation, the application should be made within 2 to 3 days of planting, and in- corporation should place the herbicides evenly into the top 1 to 2 inches of soil. Do not apply Modown after soy- beans begin to emerge. Soybeans may show stunting from Modown, especially from preemergence use followed by cold, wet soil condi- tions during early growth stages. Injury symptoms are cupping and crinkling of the first few leaves. Soybean injury is usually not reflected in yield. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan, BasaUn, or Vernam ; or it can be applied preemergence by itself or with Lasso to im- prove smartweed control. Preplant application should be done within a few days of planting soybeans, and incor- poration should distribute the herbicide uniformly in the top 1 to 2 inches of soil. The rate in sequential or tank mix combinations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preemergence Herbicides Lorox (linuron) is best suited to silt loam soils that contain 1 to 3 percent organic matter. Do not apply to very sandy soils. Lorox controls broadleaf weeds better than grass weeds. It does not control annual morning- glory, and control of cocklebur and jtmsonweed is vari- able. Accurate and uniform application, and proper rate selection are necessary to minimize the risk of crop injur)'. Tank-mix combinations allow the use of a reduced rate of Lorox to decrease the risk of soybean injury, but may also decrease the degree of weed control. Lorox is registered in tank-mix combinations witli Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of Lorox in these combinations is 1 to 1% pounds of Lorox 50W or 1 to 1% pints of Lorox 4L on silt loam soils with less than 3 percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if there is adequate rainfall. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after application. Surflan can be used for early preplant application for no- till soybeans. Do not use on soils of more than 5 percent organic matter. The rate is 1 to 2 pounds per acre of Surflan 75 W {Vi to I'/a quarts 4L) used alone or % to 1% pounds of Surflan 75W in combinations. Surflan can be tank mixed with Amiben, Lorox, Lexone, Sencor, or Dya- nap to improve broadleaf weed control. Surflan may cause stem callousing, which can lead to soybean lodging. Do not allow Surflan to contact the soybean seed. Prowl can be applied preemergence in combination with Amiben, Lorox, Lexone, or Sencor. When applied to the soil surface, Prowl may cause stem callousing, which can lead to soybean lodging. (See preplant section for more information.) Dyanap (dinoseb plus naptalam) can be applied to soybeans from the time they are planted until the imi- foliate leaves of the seedling unfold and expose the growing point. A tank mix of Dyanap plus Lasso, Dual, or Surflan is registered to improve grass control. Dyanap can also be tank mixed with Lasso plus Sencor. The Dyanap rate is 4 to 6 quarts per acre for preemergence application. Postemergence Herbicides Research suggests that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after planting. Postemergence herbicides are most effec- tive when their use is part of a planned program, and when they are applied while the ^veeds are young and tender. They should not be considered simply an emer- gency treatment. It is especially important to use timely treatments when using postemergence herbicides in nar- row-row soybeans. Postemergence herbicides are often the best choice for controlling certain problem weeds such as cocklebur, annual morningglor)', and volunteer corn. Registered combinations are shown in Table 4. For more information on conditions aff"ecting application, see the section entitled "Postemergence Herbicide Principles." Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf. It is weak on pigweed, lambsquarters, and annual morning- glory. It can be used for control of yellow nutsedge and Canada thistle but does not control annual grasses. The suggested rate for Basagran is % to 1 quart per acre, depending on weed size and species. Application should be done when weeds are small (2-3 inches) and actively growing. These conditions usually exist when the soybeans are in the unifoliate to second trifoliate stage. Spraying during warm sunny weather can also improve performance. Do not spray if rain is expected within 8 hours. Use a minimum of 20 gallons of water per acre in order to get complete weed coverage. Adding a crop-oil concentrate to Basagran may increase performance on most weeds but may cause some soybean injury. Morning- glory up to 10 inches long can be controlled with the ad- dition of 2 fluid ounces of 2,4-DB with Basagran. Do not add crop oil when mixing with 2,4-DB. Blazer (acifluorfen) should be applied when broad- leaf weeds are in the 2- to 4-inch stage and actively grow- ing. Weeds controlled include annual morningglory, pig- weed, jimsonweed, and black nightshade. Cocklebur and morningglory control can be improved with the addition Table 4. — Registered Herbicide Combinations for Postemergence Use in Soybeans Amiben Alanap X Amiben Basagran — Blazer X Dyanap — X := Registered. — =; Not registered. ♦ 2,4-DB. Blazer Butoxone* Butyrac* X X X X X X X X X 11 of 2 fluid ounces of 2,4-DB. Apply the mixture when cocklebur and morningglory measure no more tlian 10 to 12 inches and soybeans have at least five trifoliate leaves. The rate is 2 pints of Blazer 2S or 2L per acre. The Blazer 2L formulation does not include surfactant and requires the addition of a nonionic surfactant at a mini- mum of 1 pint per acre when used alone. The rate may be increased to 2 to 4 pints per acre to improve control of small escaped grasses. Surfactant addition is not rec- ommended when combining Blazer and 2,4-DB. Blazer is a contact herbicide, so leaf burn often occurs, but the crop usually recovers within 2 to 3 weeks. For ground application, use 20 to 40 gallons of water per acre applied with a minimum spray pressure of 40 psi. Do not spray if rain is expected within 6 hours. The herbicide Tackle is similar to Blazer 2L and may receive clearance in 1984. Dyanap (dinoseb plus naptalam) can be applied to soybeans after the first trifoliate leaf opens until beans become 20 inches tall. The rate is l'/2 to 2 quarts for the first and second trifoliate stages and 2 to 4 quarts per acre after that. Dyanap controls cocklebur, jimsonweed, smartweed, and annual morningglory. A split applica- tion of 2 quarts at the second trifoliate stage followed by 2 quarts 10 to 14 days later is recommended for severe weed infestations. Best results are obtained by using high pressure (40 to 60 pounds per square inch) and 8 to 10 gallons of water per acre. Use 5 gallons of water for aerial applica- tion. Although leaf bum can occur, the crop usually re- covers within 2 to 3 weeks with Uttle or no yield loss. Do not apply Dyanap to wet soybean foliage or if r£iin is expected within 6 hours. Do not add a surfactant. Amiben (chloramben) can be used for postemergence application on soybeans in the cracking to fourth tri- foliate stage, but only within 33 days after planting. Weeds controlled or suppressed include smartweed, velvetleaf, common ragweed, and pigweed. The weeds should be 1 to 4 inches tall. They may not die, but they will stop growing or become stunted so that they don't compete. The rate of Amiben 2S alone is 6 quarts; it is 5 to 6 quarts per acre in combination with either 2 to 3 fluid ounces of Butyrac 200, 2 to 3 quarts of Alanap, or VA to 2 pints of Blazer per acre. Crop oil concentrate should be used at 1 quart per acre with the Amiben alone or tank-mixed with Alanap. Do not add crop oil when tank-mixing with Butyrac. The Amiben plus Ala- nap or 2,4-DB should be applied when soybeans are in the third to sixth trifoliate stage. Apply the Amiben tank-mixed with Blazer at the appropriate rate for the weed size indicated on the Blazer label. Rescue (naptalam plus 2,4-DB) can be used for emergency postemergence control of cocklebur, giant rag- weed, and wild sunflower; it may also suppress annual morningglory. Apply 2 to 3 quarts per acre when soy- beans are about 14 inches tall and before midbloom. Use the lower rate when weeds are less than 12 inches tall. Water volume per acre is 10 to 25 gallons for ground or a minimum of 5 gallons for aerial application. Activity may not be noticeable until 10 to 14 days after applica- tion; maximum activity should occur 20 to 30 days after application. Some crop injury such as leaf twisting and terminal droop may occur. To avoid possible yield losses, do not apply Rescue to soybeans under stress from drought, disease, or injury from another herbicide. Do not apply Rescue within 60 days of harvest. Hoelon (diclof op-methyl) can control small annual grasses in the 1- to 4-leaf stage and volunteer corn. Let all of the volunteer corn emerge, but apply Hoelon before the corn that emerged first is too large to obtain adequate spray coverage. For ground application, use a minimum of 20 gallons of water per acre and 40 psi spray pressure. For aerial application, use a minimum of 5 gallons of water per acre. The Hoelon rate for annual grasses is 2 to 3'/3 pints and for volunteer com 2% to SVs pints per acre. Crop oil concentrate can be added at 1 to 2 pints per acre. Do not tank-mix Hoelon with other postemer- gence herbicides. Hoelon is a restricted-use herbicide. Poast (sethoxydim) can be used for postemergence control of annual and perennial grasses in soybeans. Use 1 pint per acre to control foxtails or panicums that are 3 to 8 inches tall or volunteer com or shattercane that is 6 to 18 inches tall. One pint per acre can also control wirestem muhly when it is 6 inches tall. Johnsongrass and quackgrass require higher rates and may also need re- treatment. See the section entitled "Specific Weed Prob- lems." Use 10 to 20 gallons of spray volume per acre for ground application and a minimum of 5 gallons per acre for aerial application. Always add crop oil concentrate at 2 pints per acre. Poast can be tank-mixed with Basa- gran, provided the Poast rate is increased by 50 percent. Sequential applications at least 24 hours apart may be more economical and practical, depending upon the weeds to be controlled and their size. Fusilade (fluazif op- butyl) can be used at V2 pint per acre when giant foxtail is 4 to 6 inches tall and other annual grasses are 2 to 4 inches tall. Use V4 pint per acre when volunteer corn is 12 to 24 inches tall or shattercane is 6 to 12 inches tall. Johnsongrass and quackgrass con- trol are discussed in the section entitled "Specific Weed Problems." Spray volume should be a minimum of 10 gallons per acre for ground application and 5 gallons per acre for aerial application. Add either crop oil concentrate at 1 percent by volume (1 gallon per 100 gallons of spray) or a nonionic surfactant at 14 percent of spray volume. Do not tank-mix Fusilade with postemergence herbicides intended for control of broadleaf weeds. Vistar (mefluldide) may be used for postemergence control of johnsongrass in soybeans south of Highway 1-70 in IlUnois. Vistar 2S is used at the rate of 1 pint per acre after the second trifoliate stage of soybeans, and when johnsongrass is less than 15 inches tall. A second application may be necessary 3 to 4 weeks after the first 12 application but no later than 60 days prior to harvest. A nonionic surfactant should be used at the rate of 1 to 2 pints per 100 gallons of spray solution. Roundup (glyphosate) can be applied through several types of selective applicators — recirculating sprayers, wipers, or rop>e wicks. This application is particularly useful for control of volunteer com, shattercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be a minimum of 6 inches above the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soy- beans. For calibration of equipment, refer to Round- up label. For recirculating sprayers and wipers, use the rates given on the label. For rope-wick applicators, mix 1 gallon of Roundup in 2 gallons of water. Paraquat Harvest Aid Paraquat and Gramoxone are registered for drying weeds in soybeans just before harvest. For indeterminate varieties (most Illinois varieties), apply when 65 percent of the seed pods have reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when at least one-half of the leaves have dropped and the rest of the leaves are turning yellow. The rate is V2 to 1 pint of Paraquat or Gramoxone per acre. The higher rate is for cocklebur. The total spray volume p>er acre is 2 to 5 gallons for aerial application or 20 to 40 gallons for ground application. Add 1 quart of nonionic surfactant per 100 gallons of spray. Do not pasture livestock within 15 days of treatment, and remove livestock from treated fields at least 30 days before slaughter. Herbicides for Sorghum Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Ap- plication may be made preemergence or postemergence. Plant seed at least 1 inch deep. Do not use preplant or preemergence on soils with less than 1 percent organic matter. Incorporated treatments may show injury if rain- fall occurs prior to or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemer- gence is 2 to 3 pounds of atrazine SOW per acre. The postemergence rate is 2'/2 to 3% pounds 80W per acre. For the 4L or 90 percent dry flowable formulations, rates are approximately equivalent to these on an active in- gredient basis. Rotational crop recommendations and weed control are the same as for atrazine used in corn. Failure to control fall panicum has been a major problem. Milogard (propazlne) has better sorghum tolerance than atrazine, but grass control is not as good. Only com or sorghum may be planted in rotation within 12 months after treatment. Ramrod (propachlor) may be used alone or in com- bination with atrazine, Milogard, Bladex, or Modown for sorghum. Ramrod will improve grass control, but rates must not be skimpy, especially on soils relatively low in organic matter. For specific rates, consult the label. Lasso (aJachlor) may be used preplant incorporated or preemergence for grain sorghum if seed is satisfactorily treated with the seed protectant Screen (flurazole). This use also applies to certain other products containing alachlor. Dual (metolachlor) or Dual plus atrazine (Bicep) can be used on sorghum seed that has had the Concep- seed treatment. These herbicides will control grasses bet- ter than does atrazine applied alone. 2,4-D may be applied postemergence for broadleaf control in 4- to 12-inch tall sorghum. Use drop nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in com (see section on com herbicides) . Banvel can be applied postemergence until sorghum is 15 inches tall or 25 days after emergence. The rate is V2 pint per acre. Do not graze or feed treated forage or silage prior to the mature grain stage. Sorghum may be injured by Banvel. Prowl (pendimethalin) may be applied to grain sorghum from the 4-inch growth stage to as late as the last cultivation primarily for control of late-season an- nual grass weeds. See the section entitled "Herbicides for Corn," subsection on postemergence soil-applied herbi- cides, for more information. Specific Weed Problems Yellow Nutsedge Yellow nutsedge is a perennial sedge with a triangular stem. It reproduces mainly by tubers. Regardless of the soil depth at which the tuber germinates, a basal bulb develops 1 to 2 inches under the soil surface. A complex system of rhizomes (underground stems) and tubers de- velops from this basal bulb. Yellow nutsedge tubers begin sprouting about May 1 in central Illinois. For the most effective control, soil-applied herbicides should be incor- porated into the same soil layer in which this basal bulb is developing. For soybeans, a delay in planting until late May al- lows time for two or three tillage operations to destroy many nutsedge sprouts. Tillage helps deplete food re- serves in nutsedge tubers. Row cultivation is helpful. Pre- plant applications of Lasso, Dual, or Vemam will also help. Lasso (alachlor) applied preplant incorporated at relatively high rates can often give good control of nut- sedge. Dual (metolachlor) can be applied at 2 to 3 pints of 8E per acre to control nutsedge. Preplant treatment is preferred to treatment at the preemergence stage. Vemam 7E (vernolate) appHed preplant at 3V^ pints per acre is also effective against yellow nutsedge. Imme- diate incorporation is necessary with Vemam. 13 Basagran (bentazon) is a postemergence treatment that can also help control nutsedge in soybeans. When nutsedge is 6 to 8 inches tall, % to 1 quart per acre can be applied. If needed, a second application can be made 7 to 10 days later. Addition of a crop-oil concentrate to Basagran may improve performance. For corn, preplant tillage before nutsedge sprouts is of little help in control. Timely cultivation gives some con- trol, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane Extra at 2% to 4 quarts or Sutan+ or Genate Plus at 4% to 7'/3 pints per acre are effective for control of yellow nutsedge in com. They must be incorporated immedi- ately. Lasso or Dual applied in com as for soybeans can also be quite effective. The combinations of Lasso, Dual, Sutan+, Genate Plus or Eradicane incorporated with atrazine may im- prove control of nutsedge while also controlling broad- leaf weeds. Atrazine or Bladex (cyanazine) is used as a postemer- gence spray to control emerged yellow nutsedge when it is small. Split applications of atrazine plus oil have been more effective than single applications. Basagran can be used in com in a manner similar to that for soy- beans. Lorox (linuron) directed postemergence spray has also given some control. Johnsongrass Johnsongrass can reproduce both from seeds and by rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the johnson- grass head begins to appear. Mowing, grazing, or culti- vating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, making them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or suppressed using certain herbicides in various cropping programs. Several preplant-incorporated herbicides can provide control of johnsongrass seedlings in soybeans or com (see the table at the end of this publication) . Treflan (trifluralin), Prowl (pendimethalin), or Basa- Hn (fluchloralin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnson- grass. They are used at VA to 2 times the normal rate each year for 2 years, and then either at the normal rate, or another suitable herbicide is used the third year before resuming a regular cropping sequence. Thorough pre- plant tillage and incorporation are necessary for satis- factory control. Be certain not to plant such crops as corn or sorghum the year following application of these herbi- cides at the higher rates. Fusilade (fluazif op-butyl) can control johnsongrass in soybeans. Apply V2 pint per acre when the weed is 12 to 18 inches tall. If regrowth occurs, apply % pint when johnsongrass is 6 to 12 inches. Always add crop oil con- centrate at 1 percent of volume. Poast (sethoxydim) can control johnsongrass in soy- beans. Apply IV2 pints plus 1 quart crop oil concentrate per acre when the johnsongrass is 15 to 20 inches tall. If regrowth occurs, apply 1 pint per acre when the john- songrass is 6 to 10 inches. Eradicane Extra can help to control rhizome johnson- grass in corn when used at a rate of 4 quarts per acre with a tillage program. Dalapwn can be used to treat emerged johnsongrass before planting com or soybeans. Apply 5 to 7 pounds per acre after the grass is 8 to 12 inches tall. Plow or disk after 3 days and then delay planting corn or soybeans at least 1 week. See the label for specific intervals. Dalapon can also be used to control johnsongrass after wheat that is not double cropped or undersowTi with a legume. A combination of mowing, timely dalapon ap- plication, and tillage has provided quite effective control. Roundup (glyphosate) can be used as a spot treat- ment to control johnsongrass in com, soybeans, or sor- ghum. Apply a 1 percent solution when johnsongrass has reached the boot to head stage and is actively growing. Use of Roundup in wick or recovery-type sprayers is effective for control of johnsongrass in soybeans. (See section on postemergence herbicides for soybeans.) Roundup may be applied in small grain stubble when johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass Quackgrass is a perennial grass with shallow rhizomes. Most preemergence herbicides will not control it. Atrazine is quite effective when used as a split appli- cation in com. Apply 2V2 pounds of atrazine 80W per acre in the fall or spring and plow 1 to 3 weeks later. Another 214 pounds per acre should be applied as a pre- plant or preemergence treatment. Postemergence appli- cation is usually less effective. A single treatment with 3% to 5 pounds per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. If more than 3 pounds of atrazine is applied per acre, plant no crops other than com or sorghum the next year. Eradicane Extra can be used to suppress quackgrass in corn where more flexibility in cropping sequence is desired. A rate of 2% quarts per acre of Eradicane Extra can be used on light infestations, while 4 quarts per acre is suggested for heavier infestations. There is some risk of com injur)', especially at the higher rate. A tank mix with atrazine should improve control. Fusilade (fluazif op-butyl) may be used for quackgrass control in soybeans at V2 pint per acre. Apply when quackgrass has 3 to 5 leaves and before it is 10 inches 14 tall. A second application of Vi pint per acre 2 to 3 weeks later may be necessary. Always add crop oil concentrate or nonionic surfactant to Fusilade. Poast (sethoxydim) can be applied in soybeans at the rate of 2 '72 pints plus 1 quart of crop oil concentrate per acre when quackgrass is 6 to 8 inches tall. If regrowth occurs, apply Wi pints per acre when the quackgrass is 6 to 8 inches high. Dalapon can be applied to quackgrass 4 to 6 inches tall in the spring at a rate of 8 pounds per acre. Plow after 4 days and delay planting com for 4 to 5 weeks. Up to 15 pounds of dalapon per acre may be used in the fall. Roundup (glyphosate) can be used for controlling quackgrass before planting either com or soybeans. Apply 2 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). Delay tillage for 3 or more days after application. Canada Thistle Canada thistle is a perennial weed that has large food reserves in its root system. There are several varieties of Canada thistle. They differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in com. Banvel (dicamba) often is a little more effective than 2,4-D and may be used alone or in combination with 2,4-D. Banvel can be used as an after-harvest treatment in wheat, corn, or soybean fields or in fallow fields. Rates vary from 1 to 2 quarts of Banvel alone or in tank-mix combinations with 2,4-D or Roundup. Fall treatments should be applied before killing frosts. For best results thistles should be fully emerged and actively growing. Fields treated in the fall with Banvel should not be planted to crops other than corn, sorghum, or wheat the next season. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in com. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Can- ada thistle in soybeans or corn when the thistles are 8 to 12 inches tall. Apply % to 1 quart per acre in a single application, or for better control make two applications of Vi to 1 quart per acre each, 7 to 10 days apart. Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow 3 or more days after application before tillage. Black Nightshade Black nightshade is an annual weed that has become an increasing problem for Illinois soybean growers. The principal problem is caused by the berries, which are about the same size as soybeans at harvest. They contain a sticky juice that can gum up a combine. Black nightshade does not present much of a problem in com but should be controlled nonetheless to help re- duce production of the weed's seed. Herbicides such as atrazine, Bladex, Banvel, Lasso, and Dual are helpful for controlling this weed in com. It can be helpful to plant suspect fields to com rather than soybeans. If soybeans must be planted, plant suspect fields last. This makes the full strength of the herbicide last longer to help control the midseason flush. Preemer- gence applications usually maintain control longer than those that are preplant incorporated. For control in soybeans. Lasso, Dual, Amiben, or Lorox at full rates or a combination of Amiben or Lorox with Lasso or Dual is helpful. Suspect fields should be monitored and a postemergence application of Blazer considered. Blazer 2L at 2 pints per acre can control nightshade when treated at the 2- to 4-leaf stage. The addition of a surfactant or crop oil to Blazer 2L is recom- mended when nightshade is beyond the 3-leaf stage. Harvest-aid sprays generally do not solve the problem because they do not make the berries fall before the soy- beans are harvested. Additional Information Not all herbicides and herbicide combinations avail- able are mentioned in this publication. Some are rela- tively new and are still being tested. Some are not con- sidered to be very well adapted to Illinois or are not used very extensively. For further information on field crop weed control, consult your county Extension adviser or write to the Department of Agronomy, N-305 Turner Hall, 1102 S. Goodwin Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. Prepared by M. D. McGlamery, professor of Weed Science, Ellery Knoke, Professor of Weed Science, Dave Pike, Associate Agronomist, Loren Bode, Pro- fessor of Agricultural Engineering, John Siemens, Professor of Agricultural Engineering, and F. W. Siife, Professor of Agronomy, all at the University of Illinois; with the assistance of George Kapusta, Professor of Plant and Soil Science, Southern Illinois University, Carbondale, and Gordon Roskamp, Associate Professor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist, USDA, and Professor of Weed Science, and E. W. Stoller, Plant Physiologist, USDA, and Professor of Agronomy, both at the University of Illinois. Issued in furtherance of Cooperative Extension V/ork, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbana-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. 15 Relative Effectiveness of Herbicides on Major Weeds This chart gives a general comparative rating. Under unfavorable conditions, some herbicides rated good or fair may give erratic or poor re- sults. Under very favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when se- lecting herbicides. Rate of herbicide used also will influence results. G = good, F = fair or variable, and P = j)oor. Grasses Broadleaf Weeds a o X o bo u a n u ei bo a u o c « b ■ u u a o c <3 w fl t- bo ^ O E 73 O o V u (a bo V c 3 C bO , c 3 O 3 O g^ O o > > < i 1 u c .^ o u o 6 U >— > V a 3 M H n! aT T3 CO JS en X bO c o s e o u V -o ill «; V t: ri E -a 1 ? o cc c 3 t3 > SOYBEANS Preplant Treflan, Prowl, Basal in F-G Sencor, Lexone + F-P P-F dinitroaniline F G G G G G F P F F F-G G P G G F G F F-G Vemam F G G G G G F-P F F-P P P F P G P P P P F Preplant or Preemergence Amiben F-G G F-G F-G F-G F P P P P P-F G F-G G F-G F F-G P F Lasso, Dual G G G G G P-F P F-G P P P F F-G G P-F P P-F P P Lasso or Dual + Sencor or Lexone F G G G G P P F P F F-G G F G F F G F F-G Lasso or Dual + Lorox' F G G G G P P P-F P F F G F-G G G F G F F-G Lorox^ F F F F F P P P P F F G F G G F G F F-G Sencor, Lexone F F F F F P P P-F P F F-G G P G G F G F F-G Postemergence Basagran F-G P P P P P P F P-F G G F-P P P F F G G F-G Blazer F P-F P P-F P P P P F-G F G F-P F-G G F G G F P Dyanap F P P P P P P P F-G G G F-G P-F F-G F F F F P 2,4-DB P-F P P P P P P P F-G G P-F F P F F F P F P Hoelon G G G F-P F P G P P P P P P P P P P P P Poast, Fusilade G G G G G G G P P P P P P P P P P P P CORN Preplant Sutan+, Eradicane F-G G G G G F-G F-G P P P P-F F G P P P P F Sutan+ or Eradicane + atrazine, Bladex F-G G G G G F-G F-G F-G F-G G G G G G F G F-G F-G Princep + atrazine G F-G F-G F F P-F P F-G F-G G G G G G G G G F Preplant or Preemergence Atrazine G F-G F P P P F G F-G G G G G G G G G F-G Bladex F-G F-G F-G F-G G P P F F-G G G G F G F-G G F F Bladex + atrazine F-G F-G F F F-G P P F-G F-G G G G G G F-G G F-G F-G Lasso, Dual F-G G G G G P-F F-G P P P F F G P-F P P-F P P Lasso or Dual + atrazine or Bladex F-G G G G G P F-G F-G F G G G G G F G F-G F Prowl + atrazine or Bladex' F G G G G F P F-G F G G G G G F G F-G F-G Ramrod' G G F F-G F P P-F P P P F P G P P P P P Postemergence Atrazine + oil F-G F-G G P P P Banvel F-G P P P P P Basagran G P P P P P Bladex F-G G G F F-G P Buctril, Brominal F-G P P P P P 2,4-D F P P P P P F P F F P P G G P-F G F F-G F G G G G G G G F G F-P F G G G P G F F G P F-G F G G F G G G G F F F G G G G F P-F G G F F G F F-G F-G F F-G ' Do not use for preplant incorporation. 18M— 10-83— 5785a-sar 1^ G':< lyoD Row Crop Weed Control Guidi THE LIBRARY OF THE !0J RSITY OF ILLINOIS URBANA-CHAMPAIGN Precautions 1 Cultural and Mechanical Control 1 Herbicide Incorp)oration 2 Chemical Weed Control 2 Names of Some Herbicides 3 Herbicide Combinations 3 Herbicide Rates 4 Postemergence Herbicide Principles 4 Conservation Tillage and Weed Control 4 No-Till and Double-Crop 5 Herbicides for Com 5 Herbicides for Soybeans 9 Herbicides for Sorghum 14 Specific Weed Problems 15 Additional Information 16 This guide is based on the results of research con- ducted by the University of Illinois Agricultural Experi- ment Station, other experiment stations, and the U.S. Department of Agriculture. Consideration has been given to the soils, crops, and weed problems of Illinois. The effectiveness of herbicides is influenced by rainfall, soil factors, weed spectrum, method of application, and formulation. Under certain conditions some herbicides may damage the crops to which they are applied. In some cases, herbicide residues in the soil may damage crops that are grown later. Precautions When selecting a herbicide, consider both the risk in- volved in using the herbicide and the yield losses caused by weeds. You can reduce risks by taking the following precautions : • Apply herbicides only to those crops for which use has been approved. • Clean tanks thoroughly when changing herbicides, especially when using a postemergence herbicide. • Correctly calibrate the sprayer and check the nozzle output and adjustment before adding herbicide to a tank. • Use recommended rates. Applying too much herbi- cide is costly and in addition may damage crops and cause illegal residues. Using too little herbicide can result in poor weed control. •Apply herbicides only at times specified on the label. Observe the recommended intervals between treatment and pasturing or harvesting of crops. • Wear goggles, rubber gloves, and other protective clothing as suggested by the label. • Guard against drift injury to nearby susceptible plants, such as soybeans, grapes, and tomatoes. Mist or vapors from 2,4-D and dicamba sprays may drift several hundred yards. When possible, operate sprayers at low pressure with tips that deliver large droplets. Spray only on calm days or make sure that wind is not moving toward susceptible crop plants and ornamentals. • Apply herbicides only when all animals and persons not directly involved in the application have been re- moved from the area. Avoid unnecessary exposure. • Check the label for the proper method of container disposal. Triple rinse, puncture, and haul metal con- tainers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or bum them in an ap- proved manner. • Return unused herbicides to a safe storage place promptly. Store them in the original containers away from unauthorized persons, particularly children. • Since formulations and labels are sometimes changed and government regulations modified, always refer to the most recent product label. This guide has been developed to help you use herbi- cides as effectively and safely as possible. However, since no guide can remove all the risk involved, the University of Illinois and its employees assume no responsibility for the results of using herbicides, even if they have been used according to the suggestions, recommendations, or directions of the manufacturer or any governmental agency. Cultural and Mechanical Control Most weed control programs combine good cultural practices, mechanical weed control, and herbicide appli- cations. Good cultural practices that aid in weed control include adequate seedbed preparation, adequate fertiliza- tion, crop rotation, planting on the proper date, use of the optimum row width, and seeding at the rate required for optimum stands. Planting in relatively warm soils helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both corn and soybeans. If weed control is adequate during that period, corn and soybeans will usually compete quite well with most of the weeds that begin growing later. Narrow rows will shade the centers faster and help the crop compete better with the weeds. However, if herbi- cides alone cannot give adequate weed control, then keep rows wide enough to allow for cultivation. Some of the newer herbicides are improving the chances of achieving adequate control without cultivation. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Use the rotary hoe after weed seeds have germinated but before most weeds have emerged. Operate it at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small weeds. Cultivate shallow to prevent injury to crop roots. Herbicides can provide a convenient and economical means of early weed control and allow for delayed and faster cultivation. Furthermore, unless the soil is crusted, it is usually not necessary to cultivate at all when herbi- cides are controlling weeds adequately. Herbicide Incorporation Soil-applied herbicides are incorporated to minimize surface loss, reduce dependence upon rainfall, and pro- vide appropriate placement of the herbicide. Sutan+ and Eradicane are incorporated soon after application to minimize surface loss from volatilization. Dinitroaniline herbicides such as Treflan are incorporated within a few hours to minimize loss due to photodecomposition and volatilization. Triazine herbicides such as atrazine and Bladex and acetamide herbicides such as Lasso and Dual may be incorporated to minimize dependence upon timely rainfall, but since these herbicides are not lost as quickly from the soil surface, the time of incorporation is less critical. Incorporation should place the herbicide uniformly in the top 1 or 2 inches of soil for best control of small- seeded annual weeds that germinate from shallow depths. Slightly deeper placement may improve the control of certain weeds from deep-germinating seed under rela- tively dry conditions. The field cultivator and tandem disk place most of the herbicide at about one-half the depth of operation. Thus for most herbicides the sug- gested depth of operation is 3 to 4 inches. Thorough incorporation with ground-drive implements may require two passes. Single-pass incorporation may result in streaked weed control, especially in wet soils. Single-pass incorporation may be adequate with some equipment, especially if rotary hoeing, cultivation, or sub- sequent herbicide treatments are used to improve weed control. If the herbicide is sufficiently covered to prevent surface loss with the first pass, the second pass can be delayed until immediately before planting. The depth and thoroughness of incorporation depend upon the type of equipment used, the depth and speed of the operation, soil texture, and soil moisture. Field cultivators and tandem disks are commonly used for in- corporation. However, disk-chisels and other combination tools are being used in some areas. Field Cultivators Field cultivators are frequently used for herbicide in- corporation. They should have three or more rows of shanks with an effective shank spacing of no more than 8 to 9 inches (a spacing of 24 to 27 inches on each of three rows) . The shanks can be equipped with points or sweeps. Sweeps usually give better incorporation, espe- cially when soil conditions are a little too wet or dry for optimal soil flow and mixing. Sweeps for "C" shank culti- vators should be at least as wide as the effective shank spacing. The recommended operating depth for the field culti- vator is 3 to 4 inches. It is usually necessary to operate it only deep enough to remove tractor tire depressions. The ground speed should be at least 6 miles per hour. The field cultivator must be operated in a level position so that the back shanks are not operating in untreated soil, which would result in streaked weed control. Two passes are recommended to obtain uniform weed control. If single-pass incorporation is preferred, the use of wider sweeps or narrower spacing with a 3- to 5-bar harrow or rolling baskets pulled behind will increase the probability of obtaining adequate weed control. Tandem Disks Tandem disk harrows invert the soil and usually place the herbicide deeper in the soil than most other incorpo- ration tools. Tandem disks used for herbicide incorpora- tion should have disk blade diameters of 20 inches or less and blade spacings of 7 to 9 inches. Larger disks are con- sidered primary tillage tools and should not be used for incorporating herbicides. Spherical disk blades give better herbicide mixing than conical disk blades. Tandem disks usually place most of the herbicide in the top 50 to 60 percent of the operating depth. For most herbicides, the suggested operating depth is from 3 to 4 inches. Two passes are recommended to obtain uni- form mixing with a double disk. A leveling device (har- row or rolling baskets) should be used behind the disk to obtain proper mixing. Recommended ground speeds are usually between 4 and 6 miles per hour. The speed should be sufficient to move the soil the full width of the blade spacing. Lower speeds can result in herbicide streaking. Combination Tools Several new tillage tools combine disk gangs, field cultivator shanks, and leveling devices. Many of these combination tools can handle large amounts of surface residue without clogging and yet leave considerable crop residue on the soil surface for erosion control. Results indicate that these combination tools may provide more uniform one-pass incorporation than does a disk or field cultivator, but one pass with them is generally no better than two passes with the disk or field cultivator. Chemical Weed Control Plan your weed-control program to fit your soils, tillage program, crops, weed problems, and farming oper- ations. Herbicide performance depends on the weather and on wise selection and application. Your decisions on herbicide use should be based on the nature and serious- ness of your weed problems. The herbicide selectivity table at the end of this guide indicates the susceptibility of our most common weed species to herbicides. Com or soybeans may occasionally be injured by some of the herbicides registered for use on those crops. To reduce crop injury, apply the herbicide at the time speci- fied on the label and at the correct rate (see section en- titled "Herbicide Rates"). Crop tolerance ratings for various herbicides are also given in the table at the end of this guide. Unfavorable conditions such as cool, wet weather, delayed crop emergence, deep planting, seedling diseases, poor soil physical conditions, and poor-quality seed may contribute to crop stress and herbicide injury. Hybrids and varieties also vary in their tolerance to herbicides and environmental stress factors. Once injured by a herbicide, plants are prone to disease. Crop planting intentions for the next season must also be considered. Where atrazine or simazine are used, you should not plant spring-seeded small grains, small-seeded legumes and grasses, or vegetables the following year. Be sure that the application of Treflan or similar herbicides for soybeans is uniform and sufficiently early to reduce the risk of injury to wheat or com following soybeans. Refer to the herbicide label for information on cropping sequence. Names of Some Herbicides Trade Common (generic) AAtrex, Atrazine atrazine Alanap naptalam Amiben chloramben Banvel dicamba Basagran bentazon Bicep metolachlor -f atrazine Bladex cyanazine Blazer acifluorfen Bronco alachlor + glyphosate Buctril, Brominal bromoxynil Butoxone, Butyrac 2,4-DB Dowpon M dalapon Dual metolachlor Dyanap naptalam plus dinoseb Eradicane EPTC plus safener Eradicane Extra EPTC plus safener and extender Evik ametryn Extrazine cyanazine plus atrazine Furloe Chloro IPC chlorprophzun Fusilade fluazif op-butyl Hoelon diclof op-methyl Laddok bentazon + atrazine Lasso alachlor Lorox, Linex linuron Milogard propazine Modown bif enox Paraquat Plus, Gramoxone paraquat Poast sethoxydim Princep, Simazine, Caliber 90 simazine Prowl pendimethalin Ramrod propachlor Rescue naptalam plus 2,4-DB Reward vernolate plus extender Roundup glyphosate Sencor, Lexone metribuzin (several ) 2,4-D Sonalan ethalfluralin Surflan oryzalin Sutan-f, Genate Plus butylate plus safener Sutazine butylate plus safener plus atrazine Treflan trifluralin Vemam vemolate Some herbicides have different formulations and con- centrations under the same trade name. No endorsement of any trade name is implied, nor is discrimination against similar products intended. Herbicide Combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package mix," while others are tank mixed. Tank mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifiable concentrate (EC) formulations with wettable powder (WP), water dispersible liquid (WDL), or water dis- persible granule (WDG) formulations. These problems can sometimes be prevented by using proper mixing pro- cedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides that are sus- pended. If using liquid fertilizers, check compatibility in a small lot before mixing a tankful. The addition of compatibility agents may be necessary. Wettable pow- ders, WDGs, or WDLs should be added to the tank be- fore ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to prevent accumulation of ma- terial on the sides and the bottom of the tank. The user can apply two treatments of the same herbi- cide (split application), or he can use two different ones, provided such uses are registered. The use of one herbi- cide after another is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant application might be followed by a preemergence application, or a soil-applied treatment might be followed by a postemergence treat- ment. One herbicide may be broadcast while the other is banded or directed. 3 Herbicide Rates Herbicide rates vary according to the time of applica- tion, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence application than for pre- plant incorporated application. Postemergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary depending on the size and species of the weeds and on whether an adjuvant is specified. Rates for combinations are usually lower than rates for herbicides used alone. The rates for soil -applied herbicides usually vary with the texture of the soil and the amount of organic matter it contains. For instance, light-colored, medium-textured soils with little organic matter require relatively lower rates of most herbicides than do dark-colored, fine- textured soils with medium to high organic matter. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemergence rather than soil-applied herbicide," depending on the herbicide and its adaptation and on crop tolerance. The rates given in this publication are, unless other- wise specified, broadcast rates for the amount of formu- lated product. If you plan to band or direct herbicides, adjust the amount per crop acre according to the per- centage of the area actually treated. Many herbicides have several formulations with different concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formulations. Postemergence Herbicide Principles Postemergence herbicides applied to growing weeds generally have foliar rather than soil action; however, some may have both. The rates and timing of applica- tions are based on weed size and climatic conditions. Weeds can usually be controlled with a lower application rate when they are small and tender. Larger weeds often require a higher herbicide rate or the addition of a spray additive, especially if the weeds have developed under drouth conditions. Herbicide penetration and action are usually greater when the temperature and relative hu- midity are high. Rainfall occurring too soon after appli- cation (1 to 8 hours, depending on the herbicide) can cause poor weed control. Translocated (hormone) herbicides can be effective with partial foliar coverage, whereas contact herbicides require more complete coverage. Foliar coverage in- creases as water volume and spray pressure are increased. Spray nozzles that produce small droplets also improve coverage. For contact herbicides, 20 to 40 gallons of water per acre are often recommended for ground appli- cation and a minimum of 5 gallons per acre for aerial application. Spray pressures of 30 to 50 psi are often suggested wdth flat-fan or hollow-cone nozzles to produce small droplets and improve canopy penetration. These small droplets are quite subject to drift. The use of a surfactant or crop oil concentrate may be recommended to improve spray coverage. These spray additives will usually improve weed control but may increase crop injury. Spray additives may be needed only under drouth conditions or on larger weeds. Crop size limitations may be specified on the label to minimize crop injury and maximize weed control. If weeds are smaller than the crop, basal-directed sprays may minimize crop injury because they place more herbi- cide on the weeds than on the crop. If the weeds are taller than the crop, rope-wick applicators or recirculating sprayers can be used to place the herbicides on the top of the weeds and minimize contact with the crop. Follow the label directions and precautions for each herbicide. Conservation Tillage and Weed Control Conservation tillage refers to tillage methods that provide eflScient crop production along with adequate control of soil erosion caused by wind and water. Erosion is controlled by protecting the soil surface with plant residue. The amount of tillage is less than that used in conventional moldboard plowing. Chisel plowing, ridge tilling, or no tillage can be used; several other systems are also available. With reduced tillage systems, there is often a greater reliance on herbicides for weed control. With these sys- tems, herbicides cannot be incorporated without covering much of the residue that is necessary for effective erosion control. The early application of preplant, preemergence, and postemergence herbicides is an alternative to incor- poration. Early preplant herbicides may be applied several weeks before planting. Early application may reduce the need for a contact herbicide at planting. However, early pre- plant application may require additional herbicides (pre- emergence or postemergence) or cultivation for satisfac- tory weed control. Table 1. — Registered No-Till Herbicide Combinatioiis Alone Combination Dual Lasso Surflan Prowl Soybeans Lorox ... PBR PR PBR PR P Lexone .... ... PBR PR PBR PR P Sencor .... . . . PBR PR PBR PR P Corn Atrazine • . . ... PBR PR PBR — — Bladex ... PBR P PBR — — Princep .... ...BR PR PBR — — Atrazine + Bladex . . ... B P PB — — . Atrazine -f- Princep . . ... PBR PR PBR — — Bicep ...PR — — — — Knockdown herbiddei: P = Paraquat, Gramoxone (paraqtiat). R = Roundup (^lyphosate) B = Bronco = Roundup + Lasso. — = Not repstered. Compared with preplant incorporated herbicides, preemergence herbicides require less tillage, but their per- formance is more dependent upon timely rainfall. How- ever, they have performed better than herbicides that are poorly incorporated. With conservation tillage, a higher application rate of surface-applied herbicides may be re- quired for satisfactory weed control, especially in fields with considerable weed infestation or crop residue. Do not, however, use a higher rate than that stated on the label. Use great care when selecting herbicides and choosing application rates. The use of effective postemergence herbicides, which depend upon foliar rather than soil action, may be a logical choice with some conservation tillage systems. No-Till and Double-Crop Com and soybeans are sometimes planted without seedbed preparation, either in last year's crop residue (no-till) or as a second crop after a small grain harvest or forage removal (double-crop). Because it conserves soil, soil moisture, and time, no-till planting has greatly improved the probability of success with double-cropping. No-till herbicides must control both existing vegetation and new weed seedlings. Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop, or weeds. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor if herbicides are applied before there is sufficient regrowth. Labeled applications of 2,4-D, Banvel, or pos- sibly Roundup can improve control of broadleaf peren- nials when used for registered crops, such as com, soy- beans, or sorghum. Several precautions should be observed in no-till crop- ping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact with herbicide sprays. (Several herbicide labels give the planting depths that are necessary to avoid possible injury.) Preemergence applications may give better weed control than preplant applications because the planting process may expose untreated soil that contains viable weed seed. The total reliance on chemical weed control and the large amounts of crop residue present under no- till cropping systems may require that the higher labeled herbicide rates be used to obtain acceptable weed control. Early preplant application of herbicides may reduce the need for a foliar knockdown herbicide. A greater re- liance on postemergence herbicides may be needed. Paraquat Plus or Grzunoxone (1 or 2 pints per acre) plus a nonionic surfactant at V2 pint per 100 gallons of diluted spray is generally used to "knock down" existing foliage before crop emergence. Smartweed, giant rag- weed, and fall panicum may not be controlled if they are over 4 to 6 inches high. A minimum of 40 gallons or more of spray per acre is suggested to ensure adequate coverage of the foliage. Paraquat and Gramoxone are re- stricted-use pesticides. Roundup (3 to 8 pints per acre) is another alternative for control of existing vegetation prior to crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can translocate to the roots to give better control of perennials. Use 10 to 40 gallons of spray volume per acre. Bronco is a for- mulated mixture of glyphosate (Roundup) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Bronco may be applied in 10 to 30 gallons of water or in 10 to 50 gallons of 28 percent or 32 percent liquid nitrogen solutions. Application with a nitrogen solution should only be made for control of annual weeds that are less than 6 inches tall. Roundup, paraquat, and Bronco are registered for use in combination with the preemergence herbicides indi- cated in Table 1 . See the sections entitled "Herbicides for Corn" and "Herbicides for Soybeans" for more informa- tion on these products. Herbicides for Corn All herbicides mentioned in this section are registered for use on field corn and also on silage corn unless other- wise specified. See Table 2 for registered combinations. Herbicide suggestions for sweet com and popcorn may be found in Circular 907, 1985 Weed Management Guide for Commercial Vegetable Growers. Growers pro- ducing hybrid seed com should check with the contract- ing company or inbred-seed producer about tolerance of the parent lines. Early Preplar)f (EPP) Interest in early preplant application is increasing, especially with the trend toward reduced tillage. With the postemergence as well as residual activity of herbi- cides such as atrazine and Bladex, early weeds such as smartweed can be controlled while they are small, and emergence of others can be curtailed. The earlier applications are made before planting, the shorter the length of control after planting. To strengthen and lengthen control, an additional application of the same or another herbicide can be considered. With AAtrex, Dual, or Bicep, preplant surface appli- cation may be made using a % rate up to 45 days before planting, followed by a Vs rate at planting. A single ap- plication can be made within 30 days before planting. Bladex may be applied early preplant at labeled rates, but if applied earlier than 15 days before planting, a split application or use of another herbicide at or after plant- ing is suggested. Banvel is approved for preplant use for com, and 2,4-D is approved in some combinations for com. Prephnf Incorporaiion Some herbicides may be applied prior to planting and incorporated. The time of application will depend on the label directions and field conditions. Herbicides with sufficient residual activity, such as AAtrex, Bicep, and Dual, may be applied early preplant up to 45 days before planting. However, if applied too early, weed control may not last as long as desired after planting. Incorporation should distribute the herbicide uniformly in about the top 2 inches of soil. Do not apply herbicides too early or in- corporate them too deeply. Sutan+, Genate Plus (butylate), Eradicane, and Eradicane Extra (EPTC) contain crop safening agents. Crop injury is unlikely, but may occur when growing conditions are unfavorable or when certain hybrids are used. Eradicane Extra also contains an extender to lengthen weed control. These herbicides control annual grass weed and can control or suppress shattercane and johnsongrass at higher rates. The rate for Sutan+ and Genate Plus is 4% to 1% pints per acre. The rate for Eradicane 6.7E is 3% to Th pints per acre. The rate for Eradicane Extra 6E is 2% to 4 quarts per acre. Use the higher rates for heavy infestations of shattercane and yellow nutsedge and for johnsongrass. These herbicides should be incorporated into the soil soon after application. Although some labels allow appli- cation up to 4 weeks prior to planting, application close to planting time is generally preferable. Some of these and other herbicides can also be mixed with dry bulk fertilizer. Sutan4- and Eradicane Extra can be injected into the soil with anhydrous ammonia. Injection should be 4 to 5 inches deep with shanks spaced no wider than 8 to 10 inches. This type of application is affected by soil moisture and physical conditions of the soil. Refer to labels for more information on fertilizer- herbicide combinations. Table 2. — Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Com A» • Tji J T, • - Atrazine Atrazine Atrazine Bladex Pnncep ^ gj^^^^ + p^j^^^p PPI only Eradicane, Eradicane Extra 1 1 1 1 — Genate Plus . . 1 1 — 1 — SutanH- 1 1 1 1 — PPI or Pre Used alone. . . 1,2,3 1,2,3 1,2 1,2,3 1,2 Dual 1,2,3 1,2 1,2 1,2 1,2 Lasso 1,2,3 1,2 2 1,2 — 1 = Preplant incorporated; 2 = preemergence; 3 = early postetnergence. — = Not registered. Sutan+, Genate Plus, or Eradicane can be tank-mixed with atrazine or Bladex to improve broadleaf control. Sutan4- or Eradicane can be tank-mixed with Princep. The atrazine rate is 2 to 3 pints of 4L or equivalent amounts of SOW or 90WDG per acre. The Bladex rate is 3 to 4 pints of 4L or 2 to 2 '/a pounds of SOW per acre. Combinations with both atrazine and Bladex are also registered. Suta2inc4- 6L is a 4:1 mixture of Sutan+ and atra- zine. The application rate is 5V4 to 10'/^ pints per acre. Sutan-f plus atrazine, as well as Sutan+, are available as granular formulations. Preplant or Preemergence Herbicides Incorporation of the following herbicides is optional, depending upon the weeds to be controlled and the likeli- hood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 weeks prior to planting or soon after planting. If rainfall is limited, in- corporation may aid performance. Com tolerance of atrazine and simazine is good, but carryover to sub- sequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble and more persistent than atrazine. Thus, Princep is usually applied preplant. Princep plus atrazine can be used in 1:1 or 2:1 combinations ; the total rate is the same as for atrazine used alone. The rate for atrazine used alone is 2¥i to 3% pounds of atrazine SOW, 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex 90WDG. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank mix combinations to improve broadleaf weed control. The rate for atrazine in combi- nations is V/2 to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to l.S pounds of AAtrex 90WDG. These rates may not provide adequate control of cockle- bur, momingglory, and velvetleaf but can reduce the risk of carryover. You can minimize carryover injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil to dilute the herbi- cide. The risk of carryover is greater after a cool, dry season and on soils with a pH over 7.3. If you use atrazine at more than 3 pounds of active ingredient per acre or if you apply after June 10, plant only com or sorghum the next year. If you use atrazine in the spring and must replant, then plant only corn or sorghum that year. Do not plant small grains, small seeded legumes, or vegetables in the fall or the following spring. Soybeans planted the year after an application of atrazine can also be affected from carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not persist in the soil as long as atrazine, but atrazine does have the advantage of better corn tolerance. Bladex provides better control than atrazine of fall panicum, giant foxtail, and some other grass weeds, but not all broadleaf weeds. Bladex can be combined with atrazine at 3:1, 2:1, or 1:1 ratios of Bladex to atrazine (see label for rates) . The higher ratios will provide better grass control, while the 1 : 1 ratio will provide better broadleaf weed control. Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of com injury. Bladex rates are I'/a to 6 pounds of SOW or 1 Vi to 4% quarts of 4L. You can lessen the risk of corn injury by using reduced rates of Bladex in combinations. Extrazine 4L is a 2:1 combination of cyanazine and atrazine. It may be applied preplant to the surface, in- corporated, or used preemergence. It is approved for use in combination with Lasso 4EC, Dual 8E, Sutan+ 6.7E, or Eradicane 6.7E. Bladex can be tank-mixed with Lasso, Dual, Ramrod, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately before planting or after planting. Do not incorporate the Prowl or Ram- rod combinations. Three-way combinations of Bladex plus atrazine plus Lasso, Dual, Sutan+, or Eradicane are registered. The addition of a limited amount of atrazine should improve broadleaf control without increasing concern about carry- over. Lasso (alachlor) or Dual (metolachlor) can be pre- plant incorporated or applied at the preemergence stage. Preplant incorporation can improve control of yellow nutsedge and can lessen dependence upon rainfall. In- corporation should distribute the herbicide evenly in the top 2 inches of soil. Lasso and Dual control annual grasses and help con- trol yellow nutsedge. You can improve broadleaf weed control by using atrazine or Bladex or both in preplant combinations or by using atrazine, Bladex, or both in preemergence combinations. Lasso can be applied anytime during the week before planting com and shallowly incorporated, or it can be used after planting but before the crop and weeds emerge and within 5 days after the last tillage operation. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate for the soil if you plan to incorporate Lasso. Dual can be applied anytime during the 2 weeks prior to planting com and shallowly incorporated, or it can be used soon after planting. The rates are VA to 4 pints of Dual 8E or 6 to 16 pounds of Dual 25G per acre. Lasso or Dual plus atrazine can be preplant incorpo- rated or applied after planting until com is 5 inches tall and grass weeds have not passed the two-leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is l'/2 to 4 quarts of Lasso or VA to 2'/2 pints of Dual 8E plus l'/2 to 2'/^ pounds of atrazine BOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds of AAtrex 90WDG. Dual is also cleared in a combina- tion with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atrazine. Bleep contains 2'/2 pounds of metolachlor (Dual) and 2 pounds of atrazine per gallon. The rate is 2 to 4 quarts per acre. Lasso/atrazine (flowable) con- tains 2'/2 pounds of alachlor (Lasso) and l'/2 pounds of atrazine per gallon. The rate is 3'/2 to 4'/^ quarts per acre. Dual or Lasso plus Bladex can be applied prior to planting and incorporated, or they can be applied during the preemergence stage after planting. The rate is 2 to 4 quarts of Lasso 4E or 114 to 2'/2 pints of Dual BE plus 1 to 3% pounds of Bladex BOW or 1 to 3 quarts of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Preemergence Herbicides Ramrod (propachlor) can be applied alone or with atrazine after the com is planted but before grasses reach the two-leaf stage. Granular formulations should be ap- plied before crop or weeds emerge. Ramrod performs well on soils with over 3 percent organic matter. Ramrod is irritating to the skin and eyes, so observe label precautions. Corn tolerance is good. It controls annual grasses and pigweed. The rate is 4 to 6 quarts of Ramrod 4L or 20 to 30 pounds of 20G per acre. Banvel (dicamba) can be applied after planting until corn is no more than 5 inches tall. The addition of Banvel in approved combinations can improve control of broad- leaf weeds without creating a risk of carryover injury the next year. Banvel may injure corn, especially if recom- mended rates are exceeded, applications are not accurate and uniform, or if com is planted too shallow (less than 1 Vz inches ) . Do not use this treatment on coarse-textured soils or soils that are low in organic matter. The rate on fine-textured soils with over 2'/2 percent organic matter is 1 pint of Banvel. Banvel is approved for use in combinations with Lasso, Dual, atrazine, Bladex, or Princep. Prowl (pendimethalin) is registered for use only on corn after planting. Incorporation of Prowl may result in serious corn injury. Use only where it is possible to cover seed adequately with soil. Prowl can control annual grasses and pigweed and provides some control of smart- weed and velvetleaf. You can improve broadleaf weed control by combining Prowl with atrazine, Bladex, or Banvel. Prowl plus atrazine or Bladex may be applied in the early postemergence period before grasses are in the two-leaf stage. These combinations may also help reduce the competition from wild proso millet. However, avoid postemergence application when com is under stress from cool, wet weather; otherwise, com injury may result. The rate for such combinations is 1 to 1 V2 quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than 1 V2 percent organic matter. Postemergence Herbicides Lasso, Dual, Ramrod, or Prowl plus atrazine, or Lasso or Dual plus Banvel can be used on corn between the preemergence and very early postemergence stages (see preemergence section). To obtain satisfactory control, apply before grasses reach the two-leaf stage. For more information on postemergence principles, see section en- titled "Postemergence Herbicide Principles." Atrazine can be applied before grass weeds are more than H4 inches high. Many annual broadleaf seedlings are more susceptible than grass weeds and may be treated until they are up to 4 inches tall. For control of some broadleaf weeds, 1.2 pounds active ingredient of atrazine may be sufficient. This rate will generally need to be in- creased to 2 pounds for control of annual grass weeds. The addition of oil-surfactant mixes or surfactants has generally increased the effectiveness of postemergence atrazine. Crop oil concentrates (80 percent oil and 20 percent surfactant) are used at the rate of 1 quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or at a rate of about 1 pint per acre. Results with the oil-surfactant mixes have generally been better than those with surfactants. Applications of atrazine and oil sometimes damage com that has been under stress from prolonged cold, wet weather or other factors. Do not use more than 2'/2 pounds of atrazine SOW, 2 quarts of atrazine 4L, or 2.2 pounds AAtrex Nine-O per acre if you mix with oil or oil concentrate. Do not add 2,4-D to the atrazine-oil treatment or severe injury may result. Mix the atrazine with water first and add the oil last. If atrazine is applied after June 10, do not plant any crop except corn or sorghum the next year, Bladex (cyanazine) can be applied through the four- leaf stage of corn growth but before weeds exceed Wz inches in height. The rate is VA to 2'/2 pounds of Bladex SOW per acre. Do not use Bladex 4L because it contains oil and can increase the potential for injury. Injury to corn may occur under cold, adverse growing conditions. The injury may only be temporary yellowing but can be more severe. Under drouthy conditions certain agricul- tural surfactants or vegetable oils may be added to Bladex SOW to improve weed control. Do not use petroleum crop oils or apply with liquid fertilizers for postemergence application. Do not apply Bladex post- emergence on corn that is under severe stress. One may combine Bladex SOW with atrazine SOW, substituting atrazine for 30 percent of the Bladex. A Bladex plus Banvel combination is also registered that allows for the addition of V2 to % pint per acre of Banvel ; no surfactant or any type of oil should be added with this combination. Banvel or Banvel II (dicamba) can be applied from emergence until corn is 36 inches tall or 15 days before tassel emergence, whichever comes first. Best results can be expected when using V2 to 1 pint of Banvel per acre when the corn is in the spike to 5-inch stage. Application at this time can offer several weeks of soil (residual) activity when the 1-pint rate is used. With this timing, crop tolerance is better than with preemergence treat- ments of Banvel. In addition, application rates can be higher than in the later postemergence treatment, and the likelihood of injury to nearby soybeans is diminished. For applications of Banvel II on corn from 5 to 36 inches tall, the preferred rate is 1 pint per acre. Banvel is labeled as an overlay (sequential) treatment following Sutan4-, Eradicane, Lasso, Dual, Bicep, Ramrod, atrazine, Bladex, Princep, Roundup, Bronco, or paraquat. Banvel is also labeled for postemergence use as a tank mix with atrazine, Bladex SOW, or 2,4-D. The post- emergence rate for Banvel is V2 pint (V4 pound active ingredient per acre) after corn is 5 inches tall. The label allows for the addition of Va to V4 pound of 2,4-D acid equivalent per treated acre. With Banvel or Banvel plus 2,4-D, drop pipes should be used on the nozzles if com is taller than S inches to help keep the spray off the com leaves and out of the whorl. For best results, use Banvel or Banvel II before June 20 with a spray volume of 20 gallons per acre and a spray pressure of no more than 20 psi to help reduce the risk to plants outside the target area. To aid in the control of hemp dogbane, Banvel is ap- proved for use at V2 pint with 1 pound acid equivalent per acre of 2,4-D LV ester or amine after corn is in the brown silk stage but at least 7 days before harvest. 2,4-D is effective in controlling many broadleaf weeds in corn. Use drop nozzles if corn is more than S inches high to decrease the possibility of injury. If you direct the nozzles toward the row, adjust the spray concentra- tion so that excessive amounts are not applied to the com. Do not apply 2,4-D to corn from the tasseling to dough stage. After the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-Ds by air or high clearance equipment to control some broadleaf weeds that may interfere with harvest or to suppress certain perennial weeds. The suggested broadcast rate of acid equivalent per acre is Ve to 14 pound of ester formulations or V2 pound of amine. This would be '/s to V2 pint of ester or 1 pint of amine for formulations with 4 pounds of 2,4-D acid equivalent per gallon. The ester forms of 2,4-D can vaporize and injure near- by susceptible plants. This vapor movement is more likely with high-volatile than with low-volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Corn is often brittle for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other symptoms of 2,4-D in- jury are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. High temperature and high humidity can increase the potential for 2,4-D injury, especially if corn is growing rapidly. If it is necessary to spray under these conditions, it may be wise to reduce the rate by about 25 percent. Com hybrids differ in their sensitivity, and the proba- bility of injury increases when corn is under stress. Buctril or Brominal (bromoxynil) may be used to control broadleaf weeds in field and silage com. It is im- portant to treat when the weeds are small. For ground applications, use 20 gallons of water per acre, a spray pressure of 40 psi, and flat fan nozzles. Bromoxynil may cause some burning of corn leaves, but the effects are usually temporary. Buctril 2E (at the rate of 1 to VA pints per acre) or Brominal 4E (at Vi to 1 pint per acre) should be applied when corn is in the 2-leaf to 14-inch stage and before weeds are 4 to 6 inches tall. Use the higher rate on larger corn and weeds. Weeds controlled include cocklebur, lambsquarters, smartweeds, jimsonweeds, common and giant ragweed, tall and ivyleaf morningglory, and black nightshade. Pigweed and velvetleaf may require the higher rate if they are near the maximum labeled stage of growth. Bromoxynil may also help control small wild or bur cucumber. Bromoxynil is less likely than 2,4-D to cause drift injury or com injury but offers less flexibility in time of application. Bromoxynil is approved for use in combination with atrazine or 2,4-D. Rates are in the range of Vi to 1.2 pounds active ingredient per acre of atrazine or 14 to '/2 pound active ingredient per acre of 2,4-D. Refer to Buctril and Brominal labels for specific rates with each product. Do not add surfactant or crop oil. Do not add Bladex to bromoxynil. Basagran (bentazon) is registered for postemergence use in corn in a manner similar to that for soybeans (see soybean section) . Since com is quite tolerant of Basagran, the addition of a crop oil concentrate is considered rela- tively safe. Basagran is also cleared at the rate of 1 to Wi pints in combination with atrazine at 0.6 to 0.9 pound of SOW, 0.6 to 0.8 pound of 90WDG, or 1 to l'/2 pints of 4L per acre. Laddok is a formulated mixture of Basa- gran plus atrazine. The rate is 2.4 to 3.6 pints per acre. Oil concentrate is added at 1 quart per acre for control of annual broadleaf weeds only. The combination is more economical than Basagran alone and will create less risk of carryover than atrazine alone. ?o%\emQT2er\CQ Soil-Applied Herbicides Prowl, Treflan, or Lasso can be applied to the soil as a postemergence treatment. It may be necessary to use drop nozzles to avoid interference from com leaves and ensure uniform application to the soil. Prowl (pendimethalin) or Treflan (trifluralin) maybe applied to the soil and incorporated after field com is 4 inches high (for Prowl) or 8 inches high (for Treflan) and up to the time of the last cultivation. The field should be cultivated to control existing weeds and cover the roots at the base of the com before application. The herbicide should then be thoroughly and uniformly in- corporated into the top inch of the soil. Prowl may not need incorporation if irrigation or rainfall occurs soon after application. Prowl can be combined with atrazine. These treatments may help control late-emerging grasses such as shattercane, wild proso millet, or fall panicum. Lasso (alachlor) may be used alone or with atrazine as a soil-applied postemergence treatment to help control midseason annual grass weeds in com that is grown for seed. Application should preferably be made after culti- vation before weeds emerge and before the crop is 40 inches tall. Directed Postemergence Herbicides Directed sprays are sometimes needed for emergency situations, especially when grass weeds become too tall to be controlled by cultivation. However, weeds are often too large for directed sprays to be effective. Directed sprays cannot be used on small corn because a height difference between corn and weeds is needed to keep the spray off the corn. Corn leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox or Linex (Hnuron) may be applied as a directed spray after corn is at least 15 inches tall (free standing) but before weeds are 8 inches tall (preferably no more than 5 inches). Linuron controls broadleaf and grass weeds. The broadcast rate is 114 to 3 pounds of Lorox 50 W or 1!4 to 3 pints of 4L per acre, depending on weed size and soil type. Add Surfactant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the corn as much as possible. Con- sider this an emergency treatment. Evik SOW (ametryn) is registered for directed use when corn is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 2'/2 pounds Evik 80 W per acre (broadcast) plus 2 quarts of surfactant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Bladex SOW (cyanazine) or Bladex SOW plus atrazine may be used as a directed spray for lay-by treatment for corn seed production fields at least 60 days before har- vest. Seed com should be at least 10 inches tall and there should be a sufficient height difference between the com and the weeds to allow the spray to cover the weeds but not touch the corn leaves. This treatment can control weeds that are up to l'/2 inches tall and suppress weeds that are a little taller. The use of nitrogen solutions as carriers and/or the addition of crop oil or surfactant can enhance control. Do not apply over the top of corn. Herbicides for Soybeans Consider the kinds of weeds expected when you select a herbicide program for soybeans, especially when grow- ing soybeans in narrow rows. The herbicide selectivity table (see last page of this guide) lists herbicides and their relative weed control ratings for various weeds. Soybeans may be injured by some herbicides. However, they usually outgrow early injury with little or no effect on yield if stands have not been significantly reduced. Significant yield decreases can result when injury occurs during the bloom to pod fill stages. Excessively shallow planting may increase the risk of injury from some herbi- cides. Accurate rate selection for soil type is especially essential for Lorox, Lexone, and Sencor. Do not apply Lorox, Lexone, Sencor, or Modown after soybeans have begun to emerge. Follow label instructions as to rates, timing, incorporation, and restrictions. For registered combinations, see Table 3. Preplant Herbicides Incorporation is required for Treflan, Sonalan, Ver- nam, and Reward. Incorporation is optional for Amiben, Dual, Lasso, Modown, and Prowl when used alone and in some combinations. Dyanap, Lorox, and Surflan should not be incorporated. Herbicides such as Dual and Surflan may be applied to the soil surface early preplant, but little if any post- emergence activity on existing vegetation should be ex- pected. Herbicides such as linuron and metribuzin can have some postemergence as well as residual activity, but the degree of postemergence activity can vary with factors such as temperature and humidity. Incorporation can improve performance if rainfall is limited and may increase the effectiveness of Dual or Lasso in controlling nutsedge. Incorporation should distribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early application of the herbicide can cause sig- nificant reductions in weed control. For more informa- tion, see the section entitled "Herbicide Incorporation." Table 3. — Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Soybeans Amiben Sencor or Lexone Amiben -|- Sencor or Lexone Lorox 1,2 1,2 1,2 PPI only Sonalan 1 1 Treflan 1 1 PPI or Pre Dual 1,2 1,2 Lasso 1,2 1,2 Prowl 1,2 1,2 Surflan* 2 2 1 = Preplant incorporated; 2 ^ preemergence. — = Not registered. • Not for preplant incorporation. Dinitroaniline herbicides registered for weed control in soybeans are Treflan, Prowl, Sonalan, and Surflan. Treflan and Sonalan should be incorporated because they have low solubility and are subject to loss by vapor- ization and photodecomposition. Incorporation is optional with Prowl, but variable weed control and soybean injury may result if Prowl is not incorporated. Incorpora- tion should distribute the herbicide uniformly in the top 2 to 3 inches of soil (see label for implement settings). Do not incorporate Surflan (see preemergence section). The dinitroaniline herbicides control annual grasses, pigweed, and lambsquarters and may provide some con- trol of smartweed and annual morningglory. Prowl and Surflan may also partially control velvetleaf. However, acceptable control of most other broadleaf weeds requires combinations or sequential treatments with other herbi- cides. Soybeans are sometimes injured by dinitroaniline herbi- cides. Plants that have been injured by incorporated treatments may be stunted and have swollen hypocotyls and shortened lateral roots. Such injuries are not usually serious. Plants injured by preemergence applications may have stem calluses at the soil surface, which can cause lodging and yield loss. Com, sorghum, and small grains may be injured if they are grown after a soybean crop that has been treated with a dinitroaniline herbicide. The symptoms are poor germination and stunted, purple plants with poor root systems. To avoid carryover, use no more than the recommended rates and be sure that application and incorporation are uniform. The likelihood of carryover increases with double cropping or late application and after a cool, dry season. Adequate tillage may help dilute herbicide residue to help alleviate a carr^'over problem. Treflan (trifluralin) can be applied alone anytime in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks prior to planting, and combinations with Amiben, Furloe, or Modown should be applied within a few days prior to planting. Incorpo- rate as soon as possible, but do not delay incorporation more than 24 hours (8 hours if soil is warm and moist). The rate is 1 to 2 pints of Treflan 4E or 10 to 20 pounds of Treflan 5G per acre. Treflan MTF is a multitempera- ture formulation that can be used to avoid problems associated with freezing in storage. Sonalan (ethalfluralin) may be applied up to 3 weeks prior to planting and should be incorporated within 2 days after application. The rate for general weed control ranges from V/z to 3 pints per acre, depending on soil texture. Sonalan may provide some control of nightshade at rates of 3 to 4'/2 pints per acre, but for this purpose it should be used in conjunction with Amiben, Dual, or Lasso or followed with Blazer. Sonalan is less likely to injure com following soybeans than is Treflan. Sonalan may be tank-mixed with Ambien, Lasso, Dual, metri- buzin, or Vemam. Prowl (pendimethalin) can be applied within 60 days (alone) or 7 days (with Sencor or Lexone) prior to planting soybeans or applied after planting (see pre- emergence section). Preplant treatments should be in- corporated within 7 days of application. Mechanical in- corporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, al- though rates for combinations with Sencor or Lexone are lower than when the herbicide is used alone. Sencor or Lexone (metribuzin) plus Treflan, Sonalan, or Prowl can be tank-mixed and applied within 7 to 14 days of planting. Incorporate uniformly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is VS to 1 pint of 4L or Vi to % pound of 75DF. Use the normal rate, or slightly less, of the dinitro- aniline herbicide (see labels). The application of Sencor or Lexone can also be split, one part being incorporated and the other part applied to the surface preemergence. This method requires two applications but can give better broadleaf control and less injury than incorporating the same total amount of Sen- cor or Lexone in a single application. 10 Amiben (chloramben) can be incorporated with Treflan, Sonalan, or Prowl. The rate is 4 to 6 quarts of Amiben 2S per acre. Amiben can also be applied and in- corporated with Treflan or Prowl plus Sencor or Lexone as a three-way combination. Vernam (vernolate) and Reward 6E (vernolate plus an extender) control annual grasses and pigweed. They sometimes provide fair control of annual morningglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vernam can be applied within 10 days prior to planting and should be incorporated im- mediately. The broadcast rate is IVi to Vh pints of Vernam 7E or 20 to 30 pounds of Vernam lOG per acre. Ver- nam plus Treflan is labeled at the rate of 1 pint of Treflan plus 2'/3 to 3 pints of Vernam 7E per acre. The combination may reduce the risk of soybean injury, but it may also decrease control of velvetleaf and yellow nut- sedge. Other labeled combinations include Vernam plus Amiben, Sonalan, Lasso, or Furloe. Preplant or Preemergence Herbicides Lasso (alachlor) or Dual (metolachlor) can be ap- plied to soybeans and preplant incorporated or applied during the preemergence stage. Lasso may be applied within 1 week of planting. Dual may be applied to the soil surface early preplant up to 30 days before planting as a single treatment. Or a % rate can be used within 45 days of planting along with a '/s rate at planting. If rainfall is limited, incorporation can improve per- formance and increase yellow nutsedge control. Soybeans are quite tolerant of Lasso or Dual. The first to second trifoliate leaves often appear crinkled and have a draw- string effect on the middle leaflet, but these symptoms should not cause concern. Lasso or Dual controls annual grasses and pigweed and can help control nutsedge and black nightshade. These herbicides can be combined with Lexone, Sencor, or Amiben (incorporated or preemergence) and with Lorox or Dyanap (preemergence only) to improve broadleaf weed control. The rate for Lasso is 2 to 4 quarts Lasso 4E or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is VA to 3 pints per acre, and the rate for Dual 25G is 6 to 12 pounds per acre. Use the higher amount for the soil when incorporating or when black nightshade or yellow nutsedge are to be controlled. The rate for combi- nations is slightly less than that for the herbicide used alone (see labels). Lasso may be applied after soybean emergence but before soybeans pass the unifoliate stage. Amiben (chloramben) can control annual grasses and many broadleaf weeds in soybeans when used at the full rate. Do not expect control of cocklebur or annual morn- ingglory. Control of velvetleaf and jimsonweed is often erratic. Amiben occasionally injures soybeans, but dam- age does not usually affect yield. Injured plants may be stunted and have abnormal, shortened roots. If rain does not occur within 3 to 5 days of an Amiben preemergence application, you should rotary hoe. Amiben is best suited to soils that have over 2.5 percent organic matter. Amiben can be applied alone or with Dual, Lasso, or Prowl as a preplant-incorporated or preemergence treat- ment. Amiben plus Sencor can also be mixed with Lasso, Dual, or Prowl as a preplant or preemergence treat- ment. Amiben can be applied as a preemergence treat- ment with Lorox, Lexone, or Sencor. The Amiben broadcast rate alone is 20 to 30 pounds of lOG, 4 to 6 quarts of 2S, or 2.4 to 3.6 pounds of 75DS per acre. The Amiben rate in combinations is 3 to 6 quarts of 2S (1.8 to 3.6 pounds of 75DS) per acre. Use the higher rate where black nightshade, velvetleaf, or common ragweed is a problem weed. Sencor or Lexone (metribuzin) can be applied any- time during the 1 to 2 weeks prior to planting and in- corporated with Dual, Lasso, Prowl, or Treflan. Incorpo- ration should distribute the herbicide evenly in the top 2 inches of soil. It can be applied preemergence by itself or with Amiben, Dual, Lasso, Prowl, Surflan, or Dyanap. Sencor or Lexone can control many annual broadleaf weeds but cannot control annual morningglory. Control of giant ragweed, jimsonweed, and cocklebur is marginal at the reduced rates necessary to minimize soybean injury. One symptom of soybean injury is yellowing (chlorosis) of the lower leaves at about the first trifoliate stage or later; it may be followed by browning of leaves and death of plants, depending upon the severity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with a pH over 7.5. Accurate, uniform application and incorporation are essential. Some soybean varieties are more sensitive than others. Injury has sometimes occurred when organophosphate insecticides such as Thimet, Counter, Dyfonate, Lorsban, or Mocap were left in applicators used for com planting and were applied to soybeans that were then being treated with metribuzin. Adjust rates accurately according to soil conditions. Do not apply to very sandy soil. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is Vi to 1 pint of 4L, or Vs to % pound of 75DF, You can use higher amounts as a split preplant and preemergence applica- tion. The higher amounts can improve broadleaf control but also increase the risk of soybean injury. Modown (bifenox) can control pigweed, lambsquar- ters, and smartweed and can provide some control of velvetleaf. Modown 4F rates are 2'/2 to 4 pints per acre. Combinations with Dual, Lasso, or Surflan, or an over- lay after Treflan can improve grass control. For preplant incorporation, the application should be made within 2 to 3 days of planting, and incorporation should distribute the herbicides uniformly in the top 1 inch of soil. Do not apply Modown after soybeans begin to emerge. Soybeans may show stunting from Modown, especially from preemergence use followed by cold, wet soil condi- 11 tions during eariy growth stages. Injury symptoms are cupping and crinkling of the first few leaves. Soybean injury is usually not reflected in yield. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan or Vernam; or it can be ap- plied preemergence by itself or with Lasso to improve smartweed control. Preplant application should be done within a few days of planting soybeans, and incorpora- tion should distribute the herbicide uniformly in the top 1 to 2 inches of soil. The rate in sequential or tank mix combinations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preemergence Herbicides Lorox or Linex (Unuron) is best suited to silt loam soils that contain 1 to 3 percent organic matter. Do not apply to very sandy soils. Linuron controls broadleaf weeds better than grass weeds. It does not control annual momingglory, and control of cocklebur and jimsonweed is variable. Accurate and uniform application and proper rate selection are necessary to minimize the risk of crop injury. Tank mix combinations allow the use of a reduced rate of linuron to decrease the risk of soybean injury, but may also decrease the degree of weed control. Linuron is registered in tank mix combinations with Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of linuron in these combinations is 1 to 1% pounds of linuron 50W or 1 to 1% pints of linuron 4L on silt loam soils that have less than 3 percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if there is adequate rainfall. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after application. Surflan can be used for early preplant application for no- till soybeans. Do not use on soils that have more than 5 percent organic matter. The rate is 1 to 2 pounds per acre of Surflan 75 W (% to V/2 quarts AS [aqueous sus- pension]) used alone or % to 1% pounds of Surflan 75 W in combinations. Surflan can be tank-mixed with Amiben, Lorox, Lexone, Sencor, or Dyanap to improve broadleaf weed control. Surflan may cause stem callusing, which can lead to soybean lodging. Do not allow Surflan to con- tact the soybean seed. For no-till soybeans, Surflan can be applied in fall or early spring over undisturbed stubble from the previous crop. Prowl can be applied preemergence in combination with Amiben, Lorox, Lexone, or Sencor. When applied to the soil surface, Prowl may cause stem callusing, which can lead to soybean lodging. (See preplant section for more information.) Dyanap (dinoseb plus naptalam) can be applied to soybeans from the time they are planted until the time the unifoliate leaves of the seedling unfold and expose the growing point. Tank mixes of Dyanap plus Lasso, Dual, or Surflan are registered to improve grass control. Dyanap can also be tank-mixed with Lasso 4E plus Sencor. The Dyanap rate is 4 to 6 quarts per acre for preemergence application. Posfemergence Herbicides Research suggests that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after planting. Postemergence herbicides are most effec- tive when their use is part of a planned program and when they are applied while the weeds are young and tender. They should not be considered simply as emer- gency treatments. It is especially important to use timely treatments when using postemergence herbicides in nar- row-row soybeans. Postemergence herbicides are often the best choice for controlling problem weeds such as cocklebur, annual morningglory, and volunteer corn. Registered combinations are shown in Table 4. For more information on conditions affecting application, see the section entitled "Postemergence Herbicide Principles." Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf. It is weak on pigweed, lambsquarters, and annual moming- glory. It can be used for control of yellow nutsedge and Canada thistle but does not control annual grasses. The suggested rate for Basagran is V* to 1 quart per acre, depending on the weed size and species. Application should be made when weeds are small (2-3 inches) and actively growing. These conditions usually exist when the soybeans are in the unifoliate to second trifoliate stage. Spraying during warm sunny weather can also improve performance. Do not spray if rain is expected within 8 hours. Use a minimum of 20 gallons of water per acre to get complete weed coverage. Adding a crop oil concen- trate to Basagran may increase performance on most weeds but may cause some soybean injury. Morningglory that is up to 10 inches long can be controlled with the addition of 2 fluid ounces of 2,4-DB with Basagran. Do not add crop oil when mixing with 2,4-DB. Blazer ( aclfluorf en ) should be appHed when broad- leaf weeds are in the 2- to 4-inch stage and actively grow- ing. Weeds controlled include annual morningglory, pig- weed, jimsonweed, and black nightshade. Cocklebur and morningglory control can be improved with the addition of 2 fluid ounces of 2,4-DB. Apply the mixture when cocklebur and momingglory measure no more than 10 to 12 inches and soybeans have at least 5 trifoliate leaves. The rate is 2 pints of Blazer 2L per acre. The Blazer 2L formulation does not include surfactant and requires the addition of a nonionic surfactant at a minimum of 1 pint per acre when used alone. The rate of surfactant may be increased to 2 to 4 pints per acre to improve con- trol of small escaped grasses. Surfactant addition is not recommended when combining Blazer and 2,4-DB. Since Blazer is a contact herbicide, leaf bum often occurs; however, the crop usually recovers within 2 to 3 weeks. For ground application, use 20 to 40 gallons of 12 Table 4. — Registered Postemergence Herbicide Combination for Broadleaf Weed Control in Soybeans Amiben Blazer Butoxone* Butyrac* Alanap Amiben Basagran Blazer Dyanap . X .' X X X X X X X X X X X X = Registered. — =: Not registered. • 2,4-DB. water per acre applied with a minimum spray pressure of 40 psi. Do not spray if rain is expected within 6 hours. The herbicide Tackle is similar in active ingredient to Blazer 2L, and label clearance is pending. A Basagran plus Blazer combination provides a means of broadening the spectrum of control. The rate is 1 to 2 pints of each product in the combination. Crop oil con- centrate may be added. Refer to individual product labels for specifics. Dyanap (dinoseb plus naptalam) at 2 quarts per acre can be applied to soybeans after the first trifoliate leaf is fully expanded until the soybeans become 20 inches tall. After 2 trifoliates are fully expanded, 3 quarts per acre may be used, Dyanap controls cocklebur, jimsonweed, and annual morningglory. A split application of 2 quarts at the first to second trifoliate stage, followed by 2 quarts 10 to 14 days later, is suggested for severe weed infestations. The addition of 2 fluid ounces per acre of 2,4-DB can improve control of some of the larger and more difficult weeds, especially if they are over 6 inches tall. Best results are obtained by using high pressure (40 to 60 psi) and 8 to 10 gallons of water per acre. Use 5 gallons of water for aerial application. Although leaf burn can occur, the crop usually recovers within 2 to 3 weeks with little or no yield loss. Do not apply Dyanap to wet soybean foliage or if rain is expected within 6 hours. Do not add a surfactant or crop oil. Amiben (chloramben) can be used for postemergence application on soybeans in the cracking to fourth tri- foliate stage, but only within 33 days after planting. This treatment can be especially helpful in controlling velvet- leaf, but smartweed, common ragweed, and pigweed may also be controlled or suppressed. Velvetleaf may be 1 to 8 inches tall and smartweed may be 1 to 3 inches tall. For ground applications, 10 to 20 gallons of water per acre, a spray pressure of 30 psi, and flat fan nozzle tips are suggested. The rate of Amiben 2S alone is 6 quarts; it is 5 to 6 quarts per acre in combination with either 2 to 3 fluid ounces of Butyrac 200, 2 to 3 quarts of Alanap, or 1 V^ to 2 pints of Blazer per acre. Crop oil con- centrate should be used at 1 quart per acre with the Amiben alone or tank-mixed with Alanap. Do not add crop oil when tank-mixing with Butyrac. The Amiben plus Alanap or 2j4-DB should be applied when soybeans are in the third to sixth trifoliate stage. Apply the Ami- ben tank-mixed with Blazer at the appropriate rate for the weed size indicated on the Blazer label but within 33 days after planting. If Amiben is also soil-applied, do not use more than a total of 12 quarts per season. Rescue (naptalam plus 2,4-DB) can be used for late-season postemergence control of cocklebur, giant rag- weed, and wild sunflower; it may also suppress annual morningglory. Apply 2 to 3 quarts per acre after soybeans are about 18 inches tall or after first bloom. Use the lower rate when weeds are less than 12 inches tall. The addition of a crop oil concentrate or surfactant can im- prove control. Application before the weeds flower is suggested for best control. The water volume per acre is 10 to 25 gallons for ground application and a minimum of 5 gallons for aerial application. If rain occurs within 6 hours, effectiveness may be reduced. Activity may not be very noticeable until 10 to 14 days after application; maximum activity should occur 20 to 30 days after appli- cation. Crop injury such as leaf twisting and terminal droop may occur. To avoid possible yield losses, do not apply Rescue to soybeans under stress from drought, disease, or injury from another herbicide. Do not apply Rescue within 60 days of harvest. Hoelon (diclof op-methyl) can control small annual grasses in the 1- to 4-leaf stage and volunteer corn. Let all the volunteer com emerge, but apply Hoelon before the corn that emerged first is too large to obtain adequate spray coverage. For ground application, use a minimum of 20 gallons of water per acre and 40 psi spray pressure. For aerial application, use a minimum of 5 gallons of water per acre. The Hoelon rate for annual grasses, in- cluding volunteer corn, is 2 to S'/s pints. Crop oil con- centrate can be added at 1 to 2 pints per acre. Do not tank-mix Hoelon with other postemergence herbicides. Hoelon is a restricted-use herbicide. Poast (sethoxydim) can be used for postemergence control of annual and perennial grasses in soybeans. The rate is 1 pint per acre to control foxtails or panicums that are 3 to 8 inches tall or volunteer corn or shattercane that is 6 to 18 inches tall. One pint per acre can also control wirestem muhly when it is 6 inches tall. Johnson- grass and quackgrass require higher rates and may also need retreatment. Use 10 to 20 gallons of spray volume per acre for ground application and a minimum of 5 gallons per acre for aerial application. Add crop oil concentrate at 2 pints per acre. Poast can be tank-mixed with Basagran, pro- vided the Poast rate is increased by 50 percent. Sequen- tial applications at least 24 hours apart may be more economical and practical, depending upon the weeds to be controlled and their size. Fusilade (fluazif op-butyl) can be used for control of annual and perennial grass weeds in soybeans. The rate is V2 pint per acre when giant foxtail is 4 to 6 inches tall and other annual grasses are 2 to 4 inches tall. Use V4 pint per acre when volunteer com is 12 to 18 inches tall or shattercane is 6 to 12 inches tall. Fusilade can also control wirestem muhly, johnsongrass, and quackgrass. 13 The spray volume should be a minimum of 10 gallons per acre for ground application and 5 gallons per acre for aerial application. Add either crop oil concentrate at 1 percent by volume ( I gallon per 100 gallons of spray) or a nonionic surfactant at Vi percent of spray volume. Apply before soybeans bloom. Do not tank-mix Fusilade with other postemergence herbicides intended for control of broadleaf weeds except as specified. A tank mix of Fusilade 4E and Blazer 2L is labeled for use without an increase in the Fusilade rate. Roundup (glyphosate) can be applied through several types of selective applicators — recirculating sprayers, wipers, or rope wicks. This application is particularly useful for control of volunteer corn, shattercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be at least 6 inches above the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soy- beans. For equipment calibration, refer to the Roundup label. For recirculating sprayers and wipers, use the rates given on the label. For rope-wick applicators, mix 1 gallon of Roundup in 2 gallons of water. A spot treat- ment with Roundup is also a good option in many fields. Paraquat Harvest Aid Paraquat and Gramoxone are registered for drying weeds in soybeans just before harvest. For indeterminate varieties (most Illinois varieties), apply when 65 percent of the seed pods have reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when at least one-half of the leaves have dropped and the rest of the leaves are turning yellow. The rate is Vz to 1 pint of Paraquat or Gramoxone per acre. The higher rate is for cocklebur. The total spray volume per acre is 2 to 5 gallons for aerial application and 20 to 40 gallons for ground application. Add 1 quart of nonionic surfactant per 100 gallons of spray. Do not pasture livestock within 15 days of treatment, and remove livestock from treated fields at least 30 days before slaughter. Herbicides for Sorghum Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Ap- plication may be made preemergence or postemergence. A preplant surface application may be made using a single application within 30 days of planting or a % plus V3 split application within 45 days of planting. Plant seed at least 1 inch deep. Do not use preplant or preemergence on soils with less than 1 percent organic matter. Incorpo- rated treatments may cause injury if rainfall occurs prior to or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemer- gence is 2 to 3 pounds of atrazine SOW per acre. The postemergence rate is 2'/2 to 3% pounds SOW per acre without crop oil or 1 .5 pounds SOW with crop oil or crop oil concentrate. For the 4L or 90 percent dry flowable formulations, rates are approximately equivalent to these on an active ingredient basis. Rotational crop recom- mendations and weed control are the same as for atrazine used in corn. Failure to control fall panicum has been a major problem. Milogard (propazine) is better tolerated by sorghum than is atrazine, but grass control is not as good. Only corn or sorghum may be planted in rotation within 12 months after treatment. Ramrod (propachlor) may be used alone or in com- bination with atrazine, Milogard, Bladex, or Modown for sorghum. Ramrod can improve grass control, but rates must not be skimpy, especially on soils that are relatively low in organic matter. For specific rates, con- sult the label. Lasso (alachlor) may be preplant incorporated or used preemergence for grain sorghum if seed is satisfac- torily treated with the seed protectant Screen (flurazole) . This use also applies to certain other products containing alachlor. Dual (metolachlor) or Dual plus atrazine (Bleep) can be used for sorghum if seed has had the Concep- seed treatment. These herbicides will control grasses bet- ter than will atrazine applied alone. An early preplant treatment of Dual or Bleep may be used in a similar manner as for com, but Concep-treated seed should still be used. 2,4-D may be applied postemergence for broadleaf control in 4- to 24-inch-tall sorghum. Use drop pines on nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in corn (see section on com herbicides) . Banvel can be applied preplant to emerged and ac- tively growing weeds up to 15 days before planting. It may be applied postemergence to sorghum that is be- tween the 3-leaf and 15-inch stage. The 3- to 5-leaf stage is preferred. The rate is V2 pint per acre. Do not graze or feed treated forage or silage prior to the mature grain stage. Sorghum may be injured by Banvel. Brominal (bromoxynil) is registered for control of broadleaf weeds in grain sorghum that is up to 14 inches tall and before weeds are 4 inches tall. It is generally safer than 2,4-D on grain sorghum. Prowl (pendimethalin) may be applied to grain sorghum from the 4-inch growth stage to as late as the last cultivation primarily for control of late-season an- nual grass weeds. See the section entitled "Herbicides for Corn," subsection on postemergence soil-applied herbi- cides, for more information. Bronco (glyphosate plus alachlor) may be used alone or with atrazine where grain sorghum is to be planted directly into a cover crop or in previous crop residue. It can control emerged annual weeds and suppress many 14 emerged perennial weeds, as well as give preemergence control. As with Lasso, grain sorghum seed must be treated with Screen. Paraquat may be used for control of annual weeds where grain sorghum is to be planted into previous crop residues. Specific Weed Problems Yellow Nutsedge Yellow nutsedge is a perennial sedge with a triangular stem. It reproduces mainly by tubers. Regardless of the soil depth at which the tuber germinates, a basal bulb develops 1 to 2 inches under the soil surface. A complex system of rhizomes (underground stems) and tubers de- velops from this basal bulb. Yellow nutsedge tubers begin sprouting about May 1 in central Illinois. For the most effective control, soil-applied herbicides should be incor- porated into the same soil layer in which this basal bulb is developing. For soybeans, a delay in planting until late May al- lows time for two or three tillage operations to destroy many nutsedge sprouts. These operations help deplete food reserves in nutsedge tubers. Row cultivation is help- ful. Preplant applications of Lasso, Dual, Vemam, or Reward will also help. Lasso (alachlor) preplant incorporated at relatively high rates can often give good control of nutsedge. Dual (metolachlor) can be applied at 2 to 3 pints of 8E per acre to control nutsedge. Preplant incorporated treatment is preferred to treatment at the preemergence stage. Vemam 7E (vemolate) applied preplant at 3V^ pints per acre is also effective against yellow nutsedge. Reward 6E is an alternative to Vemam. Immediate incorporation is necessary with Vemam or Reward. Basagran (bentazon) applied postemergence can also help control nutsedge in soybeans. When nutsedge is 6 to 8 inches tall, % to 1 quart per acre can be applied. If needed, a second application can be made 7 to 10 days later. The addition of a crop oil concentrate to Basagran may improve performance. For corn that is planted relatively early, preplant tillage before nutsedge sprouts is of little help in control. Timely cultivation gives some control, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane Extra at 2% to 4 quarts or Sutan+ or Genate Plus at 4% to 7V3 pints per acre are effective for control of yellow nutsedge in com. They must be incorporated immedi- ately. Lasso or Dual applied in corn as for soybeans can also be quite effective. The combinations of Lasso, Dual, Sutan+, Genate Plus or Eradicane incorporated with atrazine may im- prove control of nutsedge while also controlling broad- leaf weeds. Atrazine or Bladex (cyanazine) is used as a postemer- gence spray to control emerged yellow nutsedge when it is small. Split applications of atrazine plus oil have been more effective than single applications. Basagran can be used in corn in a manner similar to that for soy- beans. Lorox (Hnuron) directed postemergence spray has also given some control. Johnsongrass Johnsongrass can reproduce both from seeds and by rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the johnson- grass head begins to appear. Mowing, grazing, or culti- vating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, making them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or suppressed with the use of certain herbicides in various cropping programs. Several preplant-incorporated herbicides can provide control of johnsongrass seedlings in soybeans or corn (see the table at the end of this publication) . Treflan (trifiuralin) or Prowl (pendimethalin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnsongrass. They are used at 1 V2 to 2 times the normal rate each year for 2 years ; in the third year, either they are used at the normal rate, or an- other suitable herbicide is used before a regular cropping sequence is resumed. Thorough preplant tillage and in- corporation are necessary for satisfactory control. Be certain not to plant crops such as corn or sorghum the year following application of these herbicides at the higher rates. Fusilade (fluazif op-butyl) can control johnsongrass in soybeans. Apply V2 pint per acre when the weed is 12 to 18 inches tall. If regrowth occurs, apply % pint when johnsongrass is 6 to 12 inches. Always add crop oil con- centrate at 1 percent of volume or nonionic surfactant at 0.25 percent of volume. Poast (sethoxydim) can control johnsongrass in soy- beans. Apply I'/a pints plus 1 quart crop oil concentrate per acre when the johnsongrass is 15 to 20 inches tall. If regrowth occurs, apply 1 pint per acre when the john- songrass is 6 to 10 inches. Eradicane Extra can help control rhizome johnson- grass in corn when used at a rate of 4 quarts per acre with a tillage program; or Eradicane 6.7E can be used at 7'/3 pints per acre. Roundup (glyphosate) can be used as a spot treat- ment to control johnsongrass in corn, soybeans, or sor- ghum. Apply a 1 percent solution when johnsongrass has reached the boot to head stage and is actively growing. Use of Roundup in wick or recovery-type sprayers is effective for control of johnsongrass in soybeans. (See section on postemergence herbicides for soybeans. ) 15 Roundup may be applied in small grain stubble when johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass Quackgrass is a perennial grass with shallow rhizomes. It is found primarily in the northern part of Illinois. Atrazine is quite effective when used as a split appli- cation in corn. Apply 2'/2 pounds of atrazine SOW per acre in the fall or spring and plow 1 to 3 weeks later. Another 2'/2 pounds per acre should be applied as a pre- plan! or preemergence treatment. Postemergence appli- cation is usually less effective. A single treatment with 3% to 5 pounds per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. If more than 3 pounds of atrazine is applied per acre, plant no crops other than corn or sorghum the next year. Eradicane Extra can be used to suppress quackgrass in com where more flexibility in cropping sequence is desired. A rate of 2% quarts per acre of Eradicane Extra can be used on light infestations, while 4 quarts per acre is suggested for heavier infestations. There is some risk of corn injury, especially at the higher rate. A tank mix with atrazine should improve control. If Eradicane 6.7E is used, the rate should range from 4% to 7Vi pints per acre. Fusilade (fluazlf op-butyl) may be used for quackgrass control in soybeans at V2 pint per acre. Apply when quackgrass has 3 to 5 leaves and before it is 10 inches tall. If regrowth occurs, a second application of V2 pint per acre may be made. Always add crop oil concentrate or nonionic surfactant to Fusilade. Poast (sethoxydim) can be applied in soybeans at the rate of 2'/2 pints plus 1 quart of crop oil concentrate per acre when quackgrass is 6 to 8 inches tall. If regrowth occurs, apply l'/2 pints per acre when the quackgrass is 6 to 8 inches high. Roundup (glyphosate) can be used for controlling quackgrass before planting either corn or soybeans. Apply 1 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). Delay tillage for 3 or more days after application. Canada Thistle Canada thistle is a perennial weed that has large food reserves in its root system. There are several varieties of Canada thistle. They differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in corn. Banvel (dicamba) often is a little more effective than 2,4-D and may be used alone or in combination with 2,4-D. Banvel can be used as an after-harvest treatment in wheat, corn, or soybean fields or in fallow fields. Rates vary from 1 to 2 quarts of Banvel alone or in tank-mix combinations with 2,4-D or Roundup. Fall treatments should be applied before killing frosts. For best results thistles should be fully emerged and actively growing. Fields treated in the fall with Banvel may be planted to corn, sorghum, or wheat the next season. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in com. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Can- ada thistle in soybeans or com when the thistles are 8 to 12 inches tall. Apply % to 1 quart per acre in a single application, or for better control make two applications of % to 1 quart per acre each, 7 to 10 days apart. Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow 3 or more days after application before tillage. Black Nightshade Black nightshade is an annual weed that has become an increasing problem for Illinois soybean growers. The principal problem is caused by the berries, which are about the same size as soybeans at harvest. They contain a sticky juice that can gum up a combine. Black nightshade does not present much of a problem in com but should be controlled nonetheless to help re- duce production of the weed's seed. Herbicides such as atrazine, Bladex, Banvel, Lasso, and Dual are helpful for controlling this weed in com. It can be helpful to plant suspect fields to com rather than to soybeans. If soybeans must be planted, plant suspect fields last. This strategy helps control the mid- season flush by making the full strength of the herbicide last longer. Preemergence applications usually maintain control longer than those that are preplant incorporated. For control in soybeans. Lasso, Dual, Amiben, or linuron at full rates or a combination of Amiben or linuron with Lasso or Dual is helpful. Suspect fields should be monitored and a postemergence application of Blazer considered. Blazer 2L at 2 pints per acre can con- trol nightshade when applied at the 2- to 4-leaf stage. The addition of a surfactant or crop oil to Blazer 2L is recommended when nightshade is beyond the 3-leaf stage. Harvest-aid sprays generally do not solve the problem because they do not make the berries fall before the soy- beans are harvested. Additional Information Not all herbicides and herbicide combinations avail- able are mentioned in this publication. Some are rela- tively new and are still being tested. Some are not con- sidered to be well adapted to Illinois or are not used very extensively. For further information on field crop weed control, consult your county extension adviser or write to the Department of Agronomy, N-305 Tumer Hall, 1102 S. Goodwin Avenue, University of Illinois at Ur- bana-Champaign, Urbana, Illinois 61801. 16 Relative Effectiveness of Herbicides on Major Weeds This chart gives a general comparative rating. Under unfavorable conditions, some herbicides rated good or fair may give erratic or poor re- sults. Under very favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when se- lecting herbicides. Rate of herbicide used also will influence results. G = good, F = fair or variable, and P «= poor. Grasses Broadleaf Weeds a o u U bo e n hi u c ti S°s o s u u fc,"*" ki (3 c c:SS ih Si « 4-* J3 o 3 2 ^ tlO T3 u 3 C o bo •S 3 O < C 3 3 o u •O u c o 3 cr & d 1-4 4-» bO K ob M bO (« ca X) u s u o en c 3 > SOYBEANS Preplan! Treflan, Sonalan F-G G G G G G F P P-F P P G P-F G P P P-F P P Sencor, Lexone + dinitroaniline F G G G G G F P F F F-G G P G G F G F F-G Vemam, Reward F G G G G G P-F F P-F P P F P G P P P P F Preplant or Preemergence Amiben F-G G F-G F-G F-G F P P P P P-F G F-G G F-G F F-G P F Lasso, Dual G G G G G P-F P F-G P P P F F-G G P-F P P-F P P Lasso or Dual + Sencor or Lexone F G G G G P P F P F F-G G F-G G F F G F F-G Lasso or Dual + Lorox,' Linex* F G G G G P P P-F P F F G F-G G G F G F F-G Lorox,' Linex* F F F F F P P P P F F G F G G F G F F-G Sencor, Lexone F F F F F P P P P F F-G G P G G F G F F-G Surflan,' Prowl F-G G G G G G F P P-F P P G P G P P P-F P P-F Postemergenca Basagran F-G P P P P P P F P-F G G F-P P P F F G G F-G Blazer F P-F P P-F P P P P F-G F G F-P F-G G F G G F P Dyanap F P P P P P P P F-G G G F P-F F F F P-F F P 2,4-DB P-F P P P P P P P F-G G P-F F P F F F P F P Hoelon G G G P-F F P G P P P P P P P P P P P P Poast, Fusilade G G G G G G G P P P P P P P P P P P P Rescue F-G P P P P P P P F G F P-F P F-G P G P G P CORN Preplant Butylate, EPTG F-G G G G G F-G F-G P P P P-F F G P P P P F Butylate, EPTG + atrazine, Bladex F-G G G G G F-G F-G F-G F-G G G G G G F G F-G F-G Princep + atrazine G F-G F-G F F P-F P F-G F-G G G G G G G G G F Preplant or Preemergence Atrazine G F-G F P P P F G F-G G G G G G G G G F-G Bladex F-G F-G F-G F-G G P P F F-G G G G F G F-G G F-G F-G Bladex + atrazine F-G F-G F F F-G P P F-G F-G G G G G G F-G G F-G F-G Lasso, Dual F-G G G G G P-F F-G P P P F F-G G P-F P P-F P P Lasso or Dual + atrazine or Bladex F-G G G G G P F-G F-G F G G G G G F G F-G F Prowl + atrazine or Bladex' F G G G G F P F-G F G G G G G F G F-G F-G Ramrod' G G F F-G F P P-F P P P F P G P P P P P Postemergence Atrazine + oil F-G F-G G P P P F G G G G G G G F G G G Bjinvel F-G P P P P P P G G G G G G G G G G F Basagran G P P P P P F P-F G G F-P P P F F G G F-G Bladex F-G G G F F-G P F F F-G G F G F-G G F G F F-G Buctril, Brominal F-G P P P P P P G G G G G F G F G F-G F 2,4-D F P P P P P P G G F G F G G G P-F G F-G * Do not use for preplant incorporation. Prepared by ElleryL. Knake, Professor of Weed Science, M. D. McGlamer/, Professor of Weed Science, Dave R. Pike. Associate Agronomist, ond Michael S. Orfanedes. Assistant Agronomist, ail at the University of Illinois; with the assistance of Fred W. Slife, Professor of Agronomy at the Uni- versity of Illinois, George Kapusta, Professor of Plant and Soil Science, Southern Illinois University. Carbondole. and Gordon Roskamp. Associate Pro essor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist USDA and Professor of Weed Science, and E. W. Stoller, Plant Physiologist, USDA, and Professor of Agronomy, both at the University of Illinois. The assistance Of industry representatives is also gratefully ocknowledged. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30 1914 m cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois ai Urbana-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. 18M— 10-84 — 60302— sz 32.954 77 ?86 rt GX THE LfBRARY OF THE ivoo Row Crop Weed Control Guide FEb 1 2 UNIVERSITY OF ILLINOIS ■'R3ANA^CHAMPAIGN Precautions 1 Cultural and Mechanical Control 1 Herbicide Incorporation 2 Chemical Weed Control 2 Names of Some Herbicides 3 Herbicide Combinations 3 Herbicide Rates 3 This guide is based on the results of research con- ducted by the University of Illinois Agricultural Experi- ment Station, other experiment stations, and the U.S. Department of Agriculture. Consideration has been given to the soils, crops, and weed problems of Illinois. The effectiveness of herbicides is influenced by rainfall, soil factors, weed spectrum, method of application, and formulation. Under certain conditions some herbicides may damage the crops to which they are applied. In some cases, herbicide residues in the soil may damage crops that are grown later. Precautions When selecting a herbicide, consider both the risk in- volved in using the herbicide and the yield losses caused by weeds. You can reduce risks by taking the following precautions : • Apply herbicides only to those crops for which use has been approved. • Clean tanks thoroughly when changing herbicides, especially when using a postemergence herbicide. Use a 1 percent ammonia wash to clean out traces of 2,4-D or dicamba from the tank before spraying soybeans. • Correctly calibrate the sprayer and check the nozzle output and adjustment before adding herbicide to a tank. • Use recommended rates. Applying too much herbi- cide is costly and in addition may damage crops and cause illegal residues. Using too Uttle herbicide can result in poor weed control. •Apply herbicides only at times specified on the label. Observe the recommended intervals between treatment and pasturing or harvesting of crops. • Wear goggles, rubber gloves, and other protective clothing as suggested by the label. • Guard against drift injury to nearby susceptible plants, such as soybeans, grapes, and tomatoes. Mist or vapors from 2,4-D and dicamba sprays may drift several hundred yards. When possible, operate sprayers at low pressure with tips that deliver large droplets. Spray only on calm days or make sure that wind is not moving toward susceptible crop plants and ornamentals. Postemergence Herbicide Principles 4 Conservation Tillage and Weed Control 4 Herbicides for Com 5 Herbicides for Sorghum 10 Herbicides for Soybeans 10 Specific Weed Problems 16 Additional Information 18 • Apply herbicides only when all animals and persons not directly involved in the application have been re- moved from the area. Avoid unnecessary exposure. • Check the label for the proper method of container disposal. Triple rinse, puncture, and haul metal con- tainers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or bum them in an ap- proved manner. • Return unused herbicides to a safe storage place promptly. Store them in the original containers away from unauthorized persons, particularly children. • Since formulations and labels are sometimes changed and government regulations modified, always refer to the most recent product label. This guide has been developed to help you use herbi- cides as effectively and safely as possible. However, since no guide can remove all the risk involved, the University of Illinois and its employees assume no responsibility for the results of using herbicides, even if they have been used according to the suggestions, recommendations, or directions of the manufacturer or any governmental agency. Culfural and Mechanical Control Good cultural practices that aid in weed control in- clude adequate seedbed preparation, adequate fertiliza- tion, crop rotation, planting on the proper date, use of the optimum row width, and seeding at the rate required for optimum stands. Planting in relatively warm soils helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both com and soybeans. If weed control is adequate during that period, com and soybeans will usually compete quite well with most of the weeds that begin growing later. Narrow rows will shade tlie centers faster and help the crop compete better with the weeds. However, if herbi- cides alone cannot give adequate weed control, then keep rows wide enough to allow for cultivation. Some of the newer herbicides are improving the chances of achieving adequate control without cultivation. If a preemergence or preplant herbicide does not ap- pear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Use the rotary hoe after weed seeds have germinated but before most weeds have emerged. Operate it at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small weeds. Cultivate shallow to prevent injury to crop roots. Herbicides can provide a convenient and economical means of early weed control and allow for delayed and faster cultivation. Furthermore, unless the soil is crusted, it is usually not necessary to cultivate at all when herbi- cides are controlling weeds adequately. Herbicide Incorporation Soil-applied herbicides are incorporated to minimize surface loss, reduce dependence upon rainfall, and pro- vide appropriate placement of the herbicide. Sutan + and Eradicane are incorporated soon after application to minimize surface loss from volatilization. Treflan and Sonolan are incorporated within a few hours to minimize loss due to photodecomposition and volatilization. Tri- azine herbicides such as atrazine and Bladex and acet- amide herbicides such as Lasso and Dual may be incorpo- rated to minimize dependence upon timely rainfall, but since these herbicides are not lost as quickly from the soil surface, the time of incorporation is less critical. Incorporation should place the herbicide uniformly in the top 1 or 2 inches of soil for best control of small- seeded annual weeds that germinate from shallow depths. Slightly deeper placement may improve the control of certain weeds from deep-germinating seed under rela- tively dry conditions. The field cultivator and tandem disk place most of the herbicide at about one-half the depth of operation. Thus for most herbicides the sug- gested depth of operation is 3 to 4 inches. Thorough incorporation with ground-drive implements may require two passes. Single-pass incorporation may result in streaked weed control, especially in wet soils. Single-pass incorporation may be adequate with some equipment, especially if rotary hoeing, cultivation, or sub- sequent herbicide treatments are used to improve weed control. If the herbicide is sufficiently covered to prevent surface loss with the first pass, the second pass can be delayed until immediately before planting. The depth and thoroughness of incorporation depend upon the type of equipment used, the depth and speed of the operation, soil texture, and soil moisture. Field cultivators and tandem disks are commonly used for in- corporation. However, disk-chisels and other combination tools are being used in some areas. Field Cultivafors Field cultivators are frequently used for herbicide in- corporation. They should have three or more rows of shanks -with, an effective shank spacing of no more than 8 to 9 inches (a spacing of 24 to 27 inches on each of three rows) . The shanks can be equipped with points or sweeps. Sweeps usually give better incorporation, espe- cially when soil conditions are a little too wet or dry for optimal soil flow and mixing. Sweeps for "C" shank culti- vators should be at least as wide as the effective shank spacing. The recommended operating depth for the field culti- vator is 3 to 4 inches. It is usually necessary to operate it only deep enough to remove tractor tire depressions. The ground speed should be at least 6 miles per hour. The field cultivator must be operated in a level position so that the back shanks are not operating in untreated soil, which would result in streaked weed control. Two passes are recommended to obtain uniform weed control. If single-pass incorporation is preferred, the use of wider sweeps or narrower spacing with a 3- to 5 -bar harrow or rolling baskets pulled behind will increase the probability of obtaining adequate weed control. Tandem Disks Tandem disk harrows invert the soil and usually place the herbicide deeper in the soil than most other incorpo- ration tools. Tandem disks used for herbicide incorpora- tion should have disk blade diameters of 20 inches or less and blade spacings of 7 to 9 inches. Larger disks are con- sidered primary tillage tools and should not be used for incorporating herbicides. Spherical disk blades give better herbicide mixing than conical disk blades. Tandem disks usually place most of the herbicide in the top 50 to 60 percent of the operating depth. For most herbicides, the suggested operating depth is from 3 to 4 inches. Two passes are recommended to obtain uni- form mixing with a double disk. A leveling device (har- row or rolling baskets) should be used behind the disk to obtain projjer mixing. Recommended ground speeds are usually between 4 and 6 miles per hour. The speed should be sufficient to move the soil the full width of the blade spacing. Lower speeds can result in herbicide streaking. Combination Toots Several new tillage tools combine disk gangs, field cultivator shanks, and leveling devices. Many of these combination tools can handle large amounts of surface residue without clogging and yet leave considerable crop residue on the soil surface for erosion control. Results indicate that these combination tools may provide more uniform one-pass incorporation than does a disk or field cultivator, but one pass with them is generally no better than two passes v^th the disk or field cultivator. Chemical Weed Control Plan your weed-control program to fit your soils, tillage program, crops, weed problems, and fanning oper- ations. Herbicide performance depends on the weather and on wise selection and application. Your decisions on herbicide use should be based on the natiu-e and serious- ness of your weed problems. The herbicide selectivity table at the end of this guide indicates the susceptibility of our most common weed species to herbicides. Com or soybeans may occasionally be injured by some of the herbicides registered for use on those crops. To reduce crop injury, apply the herbicide at the time speci- fied on the label and at the correct rate (see section en- titled "Herbicide Rates"). Crop tolerance ratings for various herbicides are also given in the table at the end of this guide. Unfavorable conditions such as cool, wet weather, delayed crop emergence, deep planting, seedling diseases, poor soil physical conditions, and poor-quality seed may contribute to crop stress and herbicide injury. Hybrids and varieties also vary in their tolerance to herbicides and environmental stress factors. Once injured by a herbicide, plants are prone to disease. Crop planting intentions for the next season must also be considered. Where atrazine or simazine are used, you should not plant spring-seeded small grains, small-seeded legumes and grasses, or vegetables the following year. Be sure that the application of Treflan or similar herbicides for soybeans is uniform and sufficiently early to reduce the risk of injury to wheat or com following soybeans. Refer to the herbicide label for information on cropping sequence. Names of Some Herbicides Trade Common (generic) AAtrex, Atrazine atrazine Amiben chloramben Banvel dicamba Basagran bentazon Bleep metolachlor + atrazine Bladex cyanazine Blazer acifluorf en Bronco alachlor + glyphosate Buctril, Brominal bromoxynil Butoxone, Butyrac 2,4-DB Dowpon M dalapon Dual metolachlor Dyanap, Kleen Krop, Premerge Plus naptalam plus dinoseb Eradicane EPTG plus saf ener Eradicane Extra EPTC plus saf ener and extender Evik ametryn Furloe Chloro IPC chlorpropham Fusilade 2000 fluazifop Hoelon diclofop Lasso alachlor Lorox, Linex linuron Marksman dicamba plus atrazine Modown bif enox Paraquat Plus, Gramoxone paraquat Poast sethoxydim Princep, Simazine, Caliber 90 simazine Prowl pendimethalin Ramrod propachlor Rescue naptalam plus 2,4-DB Reward vemolate plus extender Roundup glyphosate Sencor, Lexone metribuzin (several) 2,4-D Sonalan ethalfluralin Surflan oryzalin Sutan+, Genate Plus butylate plus saf ener Sutazine butylate plus saf ener plus atrazine Treflan trifluralin Vemam vemolate Some herbicides have different formulations and con- centrations under the same trade name. No endorsement of any trade name is implied, nor is discrimination against similar products intended. Herbicide Combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package mix," while others are tank mixed. Tank mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifiable concentrate (EC) formulations with wettable powder (WP), water dispersible liquid (WDL), or water dis- persible granule (WDG) formulations. These problems can sometimes be prevented by using proper mixing pro- cedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides that are sus- pended. If using liquid fertilizers, check compatibility in a small lot before mixing a tankful. The addition of compatibility agents may be necessary. Wettable pow- ders, WDGs, or WDLs should be added to the tank be- fore ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to prevent accumulation of ma- terial on the sides and the bottom of the tank. The user can apply two treatments of the same herbi- cide (split application), or he can use two different ones, provided such uses are registered. The use of one herbi- cide after another is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant application might be followed by a preemergence application, or a soil-applied treatment nriight be followed by a postemergence treat- ment. One herbicide may be broadcast while the other is banded or directed. Herbicide Rates Herbicide rates vary according to the time of applica- tion, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence application than for pre- plant incorporated application. Postemergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary depending on the size and species of the weeds and on whether an adjuvant is specified. Rates for combinations are usually lower than rates for herbicides used alone. The rates for soil-applied herbicides usually \ary with the texture of the soil and the amount of orsranic matter it contains. For instance, light-colored, medium-textured soils with little organic matter require relatively lower rates of most herbicides than do dark-colored, fine- textured soils with medium to high organic matter. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemergence rather than soil-applied herbicide," depending on the herbicide and its adaptation and on crop tolerance. The rates given in this publication are, unless other- wise specified, broadcast rates for the amount of formu- lated product. If you plan to band or direct herbicides, adjust the amount per crop acre according to the per- centage of the area actually treated. Many herbicides have several formulations with different concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formulations. Postemergence Herbicide Principles Postemergence herbicides applied to growing weeds generally have foliar rather than soil action; however, some may have both. The rates and timing of applica- tions are based on weed size and climatic conditions. Weeds can usually be controlled with a lower application rate when they are small and tender. Larger weeds often require a higher herbicide rate or the addition of a spray additive, especially if the weeds have de\-eloped under drouth conditions. Herbicide penetration and action are usually greater when the temperature and relati\-e hu- midity are high. Rainfall occurring too soon after appli- cation (1 to 8 hours, depending on the herbicide) can cause poor weed control. Translocated (hormone) herbicides can be effective with partial foliar coverage, whereas contact herbicides require more complete coverage. Foliar coverage in- creases as water volume and spray pressure are increased. Spray nozzles that produce small droplets also improve coverage. For contact herbicides, 20 to 40 gallons of water per acre are often recommended for ground appli- cation and a minimum of 5 gallons per acre for aerial application. Spray pressures of 30 to 50 psi are often suggested with flat-fan or hollow-cone nozzles to produce small droplets and impro\'e canopy penetration. These small droplets are quite subject to drift. The use of a surfactant or crop oil concentrate may be recommended to improve spray coverage. These spray additives will usually improve weed control but may increase crop injury. Spray additives may be needed only under drouth conditions or on larger weeds. Crop size limitations may be specified on the label to minunize crop injury and maximize weed control. If weeds are smaller than the crop, basal-directed sprays may minimize crop injur)' because they place more herbi- cide on the weeds than on the crop. If the weeds are taller than the crop, rope-wick applicators or recirculating sprayers can be used to place the herbicides on the top of the weeds and minimize contact with the crop. Follow the label directions and precautions for each herbicide. Conservation Tillage and Weed Control Conservation tillage refers to tillage methods that provide efficient crop production along with adequate control of soil erosion caused by wind and water. Erosion is controlled by protecting the soil surface with plant residue. The amount of tillage is less than that used in conventional moldboard plowing. Chisel plowing, ridge tilling, or no tillage can be used; several other systems are also available. ^Vith reduced tillage systems, there is often a greater reliance on herbicides for weed control. \Vith these sys- tems, herbicides cannot be incorporated without covering much of the residue that is necessary for effective erosion control. The early application of preplant, preemergence, and postemergence herbicides is an alternative to incor- poration. Early preplant herbicides may be applied several weeks before planting. Early application may reduce the need for a contact herbicide at planting. However, early pre- plant application may require additional herbicides (pre- emergence or postemergence) or cultivation for satisfac- tory weed control. Compared with preplant incorporated herbicides, preemergence herbicides require less tillage, but their per- formance is more dependent upon timely rainfall. How- e\'er, they haxe performed better than herbicides that are poorly incorporated. \Vith consen^ation tillage, a higher application rate of surface-applied herbicides may be re- quired for satisfactory weed control, especially in fields with considerable weed infestation or crop residue. Do not, however, use a higher rate than that stated on the label. Use great care when selecting herbicides and choosing application rates. The use of effective postemergence herbicides, which depend upon foliar rather than soil action, may be a logical choice with some conser\-ation tillage systems. No-Till and Double-Crop Com, sorghum, and soybeans can be planted without seedbed preparation, either in last year's crop residue (no-till) or as a second crop after a small grain harvest or forage removal (double-crop). Because it conserx'es soil, soil moisture, and time, no-till planting has greatly improved the probability of success with double-cropping. Several precautions should be obser\-ed in no-till crop- ping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact with herbicide sprays. (Several herbicide labels give the planting depths that are necessary to avoid possible injury.) Preemergence applications may give better weed control than preplant applications because the planting process may expose untreated soil that contains viable weed seed. The total reliance on chemical weed control and the large amounts of crop residue present under no- till cropping systems may require that the higher labeled herbicide rates be used to obtain acceptable weed control. Existing Vegetation Control in Reduced Tillage Program Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop, or weeds. Perennial legume sods can often be controlled prior to planting corn or sorghum by preplant applications of 2,4-D or Banvel. Perennial grass sods can sometimes be controlled with preplant applications of Roundup. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor if herbicides are applied before there is sufficient regrowth. Existing vegetation which consists of small annual weeds less than 2 inches may not require the necessity of utilizing paraquat or Roundup as knockdown herbicides. Residual herbicides which also have postemergence ac- tivity may often control existing vegetation. Bladex, atra- zine, Sencor or Lexone, and Lorox or Linex have both preemergence and postemergence activity. Postemergence herbicides can also often be used to control existing vege- tation. Poast is labeled to control existing grass weeds prior to planting soybeans. Early preplant application of labeled residual herbi- cides can often prevent existing vegetation from being a problem before planting. The earlier applications are made before planting, the shorter the length of control after planting. To strengthen or lengthen control, an additional application of the same or another herbicide can be considered. Paraquat Plus or Gramoxone (1 or 2 pints per acre) plus a nonionic surfactant at V2 pint per 100 gallons of diluted spray can be used to "knock down" existing foliage before crop emergence. Smartweed, giant rag- weed, and fall panicum may not be controlled if they are over 4 to 6 inches high. A minimum of 40 gallons or more of spray per acre is suggested to ensure adequate coverage of the foliage. Paraquat can be applied with certain liquid fertilizers. Do not apply with suspension or high phos- phate liquid fertilizers. Paraquat and Gramoxone are re- stricted-use pesticides. Roundup (3 to 8 pints per acre) is another alternative for control of existing vegetation prior to crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can translocate to the roots to give better control of perennials. Use 10 to 40 gallons of spray volume per acre. Roundup + 2,4-D can be used in some situations to improve broadleaf control. Bronco is a formulated mixture of glyphosate (Roundup) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Bronco may be applied in 10 to 30 gallons of water or in 10 to 50 gallons of 28 percent or 32 percent liquid nitrogen solutions. Application with a nitrogen solution should only be made for control of annual weeds that are less than 6 inches tall. Roundup, paraquat, and Bronco are registered for use in combination with the preemergence herbicides indi- cated in Table 1. See the sections entitled "Herbicides for Com" and "Herbicides for Soybeans" for more informa- tion on these products. Herbicides for Corn All herbicides mentioned in this section are registered for use on field corn and also on silage com unless other- wise specified. See Table 2 for registered combinations. Herbicide suggestions for sweet corn and popcorn may be found in Circular 907, 1986 Weed Management Guide for Commercial Vegetable Growers. Growers pro- ducing hybrid seed corn should check with the contract- ing company or inbred-seed producer about tolerance of the parent lines. Preplant Not Incorporated Interest in early preplant application is increasing, especially with the trend toward reduced tillage. Bladex and atrazine have postemergence as well as residual ac- tivity. Early weeds such as smartweed can be controlled while they are small, and emergence of others can be curtailed. With AAtrex, Dual, or Bicep, preplant surface appli- cation may be made using a % rate up to 45 days before planting, followed by a V3 rate at planting. A single ap- plication can be made within 30 days before planting. Bladex may be applied early preplant at labeled rates, but if applied earlier than 15 days before planting, a split application or use of another herbicide at or after plant- ing is suggested. Banvel or 2,4-D are labeled in mixture with Bladex, Bladex plus atrazine, and Bicep for mini- mum or no-till corn. Table 1. — Registered No-Till Herbicide Combinations Alone Soybeans Amiben PR Lorox PBR L«one PBR Sencor PBR Com Atrazine PBR Bladex PBR Princep BR Atrazine + Bladex B Atrazine + Princep PBR Bicep PR — Knockdown herbicide*: P ^ Paraquat, Gramoxone (paraquat) R =: Roundup (glyphosate) . B = Bronco ^ Roundup -\- Lasso. — = Not registered. Combination Dual Lasso Surflan Prowl PR PR PR PR PR PBR PR P PR PBR PR P PR PBR PR P PR PBR P PBR PR PBR — — P PB — — PR PBR Table 2. — Registered Herbicide Combinations for Preplan! Incorporated ( PPI ) , Preemergence ( Pre ) , or Early Postemergence (EPoE) Application in Com Atrazine Bladex n . Atrazine Atrazine Pnncep ^ gj^^^^ ^ Princep PPI only Eradicane, Eradicane Extra 1 1 1 I — Genate Plus.. 1 1 — J — Sutan+ 1 1 1 » — PPI or Pre or EPoE Used alone... 1,2,3 1,2,3 1,2 1,2,3 1,2 Dual 1,2,3 1,2 1,2 1,2 1,2 Lasso 1,2,3 1,2 2 1.2 — 1 = Prrplant incorrjorated ; 2 = preemergence; 3 = early portemergence. — = Not registered. Banvel (dicamba) can be used as a preplant herbicide prior to planting com or sorghum. The rate is 1 to 2 pints per acre. It is suggested that you delay planting com 1 week and sorghum 1 to 2 weeks after application. Roundup can be used preplant to com or sorghum at '/4 to 1 pint (12 to 16 fluid ounces) per acre to control small annual weeds. Use 5 to 10 gallons of water per acre plus a surfactant. Roundup may be mixed with Banvel or 2,4-D. Prephnf Incorporation Some herbicides may be applied prior to planting and incorporated. The time of application will depend on the label directions and field conditions. Herbicides with sufficient residual activity, such as AAtrex, Bicep, and Dual, m.ay be applied eariy preplant up to 45 days before planting. However, if applied too early, weed control may not last as long as desired after planting. Incorporation should distribute the herbicide uniformly in about the top 2 inches of soil. Do not apply herbicides too early or in- corporate them too deeply. Sutan+, Genate Plus (butylate), Eradicane, and Eradicane Extra (EPTC) contain crop safening agents. Crop injury is unlikely, but may occur when growing conditions are unfavorable or when certain hybrids are used. Eradicane Extra also contains an extender to lengthen weed control. These herbicides control annual grass weeds and can control or suppress shattercane and johnsongrass at higher rates. The rate for Sutan+ and Genate Plus is 4% to VA pints per acre. The rate for Eradicane 6.7E is 4% to 7Vi pints per acre. The rate for Eradicane Extra 6E is SVs to 8 pints per acre. Use the higher rates for heavy infestations of shattercane and yellow nutsedge and for johnsongrass. These herbicides should be incorporated into the soil soon after application. Although some labels allow appli- cation up to 4 weeks prior to planting, application close to planting time is generally preferable. Sutan+, Genate Plus, Eradicane, or Eradicane Extra can be tank-mixed with atrazine or Bladex to improve broadleaf control. Sutan4- or Eradicane can be tank- mixed with Princep. The atrazine rate is 2 to 3 pints of 4L or equivalent amounts of SOW or 90WDG per acre. The Bladex rate is 3 to 4 pints of 4L or 2 to 2V2 pounds of SOW per acre. Three-way combinations with atrazine plus Bladex are also registered. Sutazine4- 6-ME is a 4:1 mixture of Sutan+ and atra- zine. The application rate is 5V4 to 10'/2 pints per acre. Sutazine-f- and Sutan4- are available as granular formulations. Preplant or Preemergence Herbicides Incorporation of the following herbicides is optional, depending upon the weeds to be controlled and the likeli- hood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 weeks prior to planting or soon after planting. If rainfall is limited, in- corporation may aid performance. Com tolerance of atrazine and simazine is good, but carryover to sub- sequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble and more persistent than atrazine. Thus, Princep is usuallv applied preplant. Princep plus atrazine can be used in 1:1 or 2:1 combinations ; the total rate is the same as for atra/ine used alone. The rate for atrazine used alone is 2Vi to 3'4 pounds of atrazine ROW. 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex 90WDG. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank mix combinations to improve broadleaf weed control. The rate for atrazine in combi- nations is IV^ to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to 1.8 pounds of AAtrex 90WDG. These rates may not provide adequate control of cockle- bur, momingglory, and velvetleaf but can reduce the risk of carryover. You can minimize carryover injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil to dilute the herbi- cide. The risk of carryover is greater after a cool, dry season and on soils with a pH over 7.3. If you use atrazine at more than 3 poimds of active ingredient per acre or if you apply after June 10, plant only com or sorghum the next year. If you use atrazine in the spring and must replant, then plant only com or sorghum that year. Do not plant small grains, small seeded legumes, or vegetables in the fall or the following spring. Soybeans planted the year after an application of atrazine can also be affected from carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not jDersist in the soil as long as atrazine, but atrazine does have the advantage of better com tolerance. Bladex provides better control than atrazine of fall panicum, giant foxtail, and some other grass weeds, but not all broadleaf weeds. Bladex can be combined with atrazine at 3:1, 2:1, or 1:1 ratios of Bladex to atrazine (see label for rates) . The higher ratios will provide better grass control, while the 1 : 1 ratio will provide better broadleaf weed control. Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of com injury. Bladex rates are 1 Vi to 6 pounds of SOW, 1.35 to 5.3 pounds of Bladex 90DF, or VA to 4% quarts of 4L. You can lessen the risk of com injury by using reduced rates of Bladex in combinations. Bladex can be tank-mixed with Lasso, Dual, Ramrod, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately before planting or after planting. Do not incorporate the Prowl or Ram- rod combinations. Three-way combinations of Bladex plus atrazine plus Lasso, Dual, Sutan+, or Eradicane are registered. The addition of a limited amount of atrazine should improve broadleaf control without increasing concern about carry- over. Lasso (alachlor) or Dual (metolachlor) can be pre- plant incorporated or applied at the preemergence stage. Preplant incorporation can improve control of yellow nutsedge and can lessen dependence upon rainfall. In- corporation should distribute the herbicide evenly in the top 2 inches of soil. Lasso and Dual control annual grasses and help con- trol yellow nutsedge. You can improve broadleaf weed control by using atrazine or Bladex or both in either a preplant or in a preemergence combination. Lasso can be applied anytime during the week before planting com and shallowly incorporated, or it can be used after planting but before the crop and weeds emerge and within 5 days after the last tillage operation. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate for the soil if you plan to incorporate Lasso. Dual can be applied anytime during the 2 weeks prior to planting corn and shallowly incorporated, or it can be used soon after planting. The rates are Vh to 4 pints of Dual 8E or 6 to 16 pounds of Dual 25G per acre. Lasso or Dual plus atrazine can be preplant incorpo- rated or applied after planting until corn is 5 inches tall and grass weeds have not passed the two-leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is VA to 4 quarts of Lasso or 114 to 2'/2 pints of Dual 8E plus l'/2 to 2V2 pounds of atrazine SOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds of AAtrex 90WDG. Dual is also cleared in a combination with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atrazine. Bleep contains a 5:4 ratio of metolachlor (Dual) : atrazine per gallon. The rate is 2 to 4 quarts of Bleep 4.5L or l'/2 to 3 quarts of Bleep 6L per acre. Lasso/atrazine (flowable) contains 2'/2 pounds of ala- chlor (Lasso) and VA pounds of atrazine per gallon. The rate is 3'/2 to 4'/2 quarts per acre. Dual or Lasso plus Bladex can be applied prior to planting and incorporated, or they can be applied during the preemergence stage after planting. The rate is 2 to 4 quarts of Lasso 4E or VA to 2'/2 pints of Dual 8E plus 1 to 3% pounds of Bladex SOW or 1 to 3 quarts of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Preemergence Herbicides Ramrod (propachlor) can be applied alone or with atrazine after the com is planted but before grasses reach the two-leaf stage. Granular formulations should be ap- plied before crop or weeds emerge. Ramrod performs well on soils with over 3 percent organic matter. Ramrod is irritating to the skin and eyes, so observe label precautions. Com tolerance is good. It controls annual grasses and pigweed. The rate is 4 to 6 quarts of Ramrod 4L or 20 to 30 pounds of 20G per acre. Banvel (dicamba) can be applied alone after planting until corn is no more than 5 inches tall. Banvel is ap- proved for use in combinations with Lasso, Dual, atrazine, or Bladex. Banvel may injure corn, especially if recom- mended rates are exceeded, applications are not accurate and uniform, or if corn is planted too shallow (less than l'/2 inches). Do not use this treatment on coarse-textured soils or soils that are low in organic matter. The rate on fine-textured soils with over 2'/2 percent organic matter is 1 pint of Banvel. Prowl (pendimethalin) is registered for use only on com after planting. Incorporation of Prowl may result in serious com injury. Use only where it is possible to cover seed adequately with soil. Prowl can control annual grasses and pigweed and provides some control of smart- weed and velvetleaf. You can improve broadleaf weed control by combining Prowl with atrazine, Bladex, or Banvel. Prowl plus atrazine or Bladex may be applied In the early postemergence period before grasses are in the two-leaf stage. These combinations may also help reduce the competition from wild proso millet. However, avoid postemergence application when com is under stress from cool, wet weather; otherwise, corn injury may result. The rate for such combinations is 1 to l'/2 quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than 1 Vz percent organic matter. Postemergence Herbicides Lasso, Dual, Ramrod, or Prowl plus atrazine, or Lasso or Dual plus Banvel can be used on com between the preemergence and very early postemergence stages (see preemergence section). To obtain satisfactory control, apply before grasses reach the two-leaf stage. For more information on postemergence principles, see section en- titled "Postemergence Herbicide Principles." Atrazine can be applied before grass weeds are more than IV^ inches high. Many aimual broadleaf seedlings axe more susceptible than grass weeds and may be treated until they are up to 4 inches tall. For control of some broadleaf weeds, 1.2 pounds active ingredient of atrazine may be sufficient. This rate will generally need to be in- creased to 2 pounds for control of annual grass weeds. The addition of oil-surfactant mixes or surfactants has generally increased the effectiveness of postemergence atrazine. Crop oil concentrates (80 percent oil and 20 percent surfactant) are used at the rate of 1 quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or at a rate of about 1 pint per acre. Results with the oil-surfactant mixes have generally been better than those with surfactants. Applications of atrazine and oil sometimes damage com that has been under stress from prolonged cold, wet weather or other factors. Do not use more than 2¥i pounds of atrazine SOW, 2 quarts of atrazine 4L, or 2.2 pounds AAtrex Nine-O per acre if you mix with oil or oil concentrate. Do not add 2,4-D to the atrazine-oil treatment or severe injury may result. Mix the atrazine with water first and add the oil last. If atrazine is applied after June 10, do not plant any crop except corn or sorghum the next year. Bladex (cyanazine) can be applied through the four- leaf stage of com growth but before weeds exceed IV2 inches in height. The Bladex rate is VA to 2'/2 pounds of SOW or 1.1 to 2.2 pounds of 90DF per acre. Do not use Bladex 4L because it contains oil and can increase the potential for injury. Injury to corn may occur under cold, adverse growing conditions. The injury may only be temporary yellowing but can be more severe. Under drouthy conditions certain agricultural surfactants or vegetable oils may be added to Bladex SOW to improve weed control. Do not use petroleum crop oils or apply with liquid fertilizers for postemergence application. Do not apply Bladex postemergence on corn that is under severe stress. One may combine Bladex SOW with atrazine SOW, substituting atrazine for 30 percent of the Bladex. A Bladex plus Banvel combination is also registered that allows for the addition of V2 to % pint per acre of Banvel ; no surfactant or any type of oil should be added with this combination. Banvel (dicamba) can be applied from emergence until corn is 36 inches tall or 15 days before tassel emer- gence, whichever comes first. Best results can be ex- pected when using V2 to 1 pint of Banvel per acre when the com is in the spike to 5-inch stage. Application at this time can offer several weeks of soil (residual) activity when the 1-pint rate is used. With this timing, crop toler- ance is better than with preemergence treatments of Banvel. In addition, application rates can be higher than in the later postemergence treatment, and the likelihood of injury to nearby soybeans is diminished. For applica- tions on com from 5 to 36 inches tall, the rate is V2 pint per acre. Banvel is labeled as an overlay (sequential) treatment following Sutan+, Eradicane, Lasso, Dual, Bicep, Ramrod, atrazine, Bladex, Princep, Roundup, Bronco, or paraquat. Banvel is also labeled for postemergence use as a tank mix with atrazine, Bladex SOW, or 2,4-D. The post- emergence rate for Banvel is V2 pint (V4 pound active ingredient per acre) after com is 5 inches tall. The label allows for the addition of Vs to V* pound of 2,4-D acid equivalent per treated acre. With Banvel or Banvel plus 2,4-D, drop pipes should be used on the nozzles if com is taller than S inches to help keep the spray off the com leaves and out of the whorl. For best results, use Banvel before June 20 with a spray volume of 20 gallons per acre and a spray pressure of no more than 20 psi to help reduce the risk to plants outside the target area. To aid in the control of hemp dogbane, Banvel is ap- proved for use at V2 pint with 1 pound acid equivalent per acre of 2,4-D LV ester or amine after com is in the brown silk stage but at least 7 days before harvest. Marksman (dicamba + atrazine) is a formulated mix- ture of 1.1 pound dicamba (active ingredient in Banvel) and 2.1 pounds of atrazine per gallon. The rate is 2 to 3.5 pints per acre depending on the soil texture and organic matter. On most Illinois soils, the rate is 3.5 pints per acre or 0.4S pound of dicamba and 0.92 pound of atrazine per acre. Marksman is cleared as a tank-mix and in sequential combinations with many other herbicides. Marksman may be applied to actively growing weeds prior to, during, or after planting but before com exceeds the 5-leaf stage. In most conventional tillage applications the recommended timing would be emergence to the 5- leaf stage of com. Most annual broadleaf weeds should be controlled, and some perennial broadleaf weeds should be suppressed. This formulated mixture will be targeted at the velvetleaf market in Illinois where Banvel has needed some help. 2,4-D is effective in controlling many broadleaf weeds in com. Use drop nozzles if com is more than 8 inches high to decrease the possibility of injury. If you direct the nozzles toward the row, adjust the spray concentra- tion so that excessive amounts are not applied to the com. Do not apply 2,4-D to com from the tasseling to dough stage. After the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-Ds by air or high clearance equipment to control some broadleaf weeds that may interfere with harvest or to suppress certain perennial weeds. Do not forage or feed fodder for 7 days after treatment. The suggested broadcast rate is Vs to V2 pint of ester or 1 pint of amine for formulations with 3.S pounds of 2,4-D acid equivalent per gallon. Use equivalent rates with other formulation concentrations. Use proportionately less when using directed nozzles. The ester forms of 2,4-D can vaporize and injure near- by susceptible plants. This vapor movement is more likely with high-volatile than with low-volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Com is often brittle for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other symptoms of 2,4-D in- jury are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. High temperature and high humidity can increase the potential for 2,4-D injury, especially if com is growing rapidly. If it is necessary to spray under these conditions, it may be wise to reduce the rate by about 25 percent. Com hybrids differ in their sensitivity, and the proba- bility of injury increases when corn is under stress. Buctril or Brominal (bromoxynil) may be used to control broadleaf weeds in field and silage com. It is im- portant to treat when the weeds are small. For ground applications, use 20 gallons of water per acre, a spray pressure of 30 psi, and flat fan nozzles. Buctril 2E rates are 1 to VA pints per acre when corn and weeds are in the 3- to 8-leaf stage. Brominal 4E rates are 14 to 1 pint per acre when corn is in the 2-leaf to 14-inch stage and before weeds are 4 to 6 inches tall. Use the higher rate on larger com and weeds. Most an- nual broadleaved weeds are controlled. Larger pigweed and velvetleaf may require the higher rate, or a combina- tion with atrazine. Atrazine 4L at 0.5 to 1.0 qviart (equivalent rates of 80 W or 90DF) can be combined with Buctril or Brominal. Do not add Bladex to bromoxynil. Bromoxynil will not volatilize and cause the drift injury associated with 2,4-D or Banvel. Bromoxynil, under some conditions, may cause some burning of corn leaf tips, but the effects are usually temporary. Do not add surfactant or crop oil to Buctril or Brominal. Basagran (bentazon) is registered for postemergence use in corn similar to that for soybeans (see soybean section). The rate is IV2 to 2 pints of Basagran 2S per acre. Crop oil concentrate can be added at one quart per acre. Basagran is also cleared at the rate of 1 to V/2 pints per acre in combination with atrazine at 0.6 to 1.0 pound of BOW, 0.6 to 0.9 pound of 90DF, or 1 to l'/2 pints of 4L per acre. Crop oil concentrate is added at 1 quart per acre. This combination controls only annual broadleaf weeds and not annual grasses. The combination provides better control of pigweed and lambsquarters than Basagran alone, and will create less risk of carry- over than atrazine alone. Roundup (glyphosate) may be applied as a spot treat- ment in com prior to silking. For applications made on a spray-to-wet basis use a 1 to 2 percent solution of Roundup in water. For motorized spot treatments where less than complete coverage of weeds may result, use a 5 percent solution. Avoid contact of spray with the corn. Add a dye for increased visibility. Postemergence Soil-Applied Herbicides Prowl, Treflan, or Lasso can be applied to the soil as a postemergence treatment. It may be necessary to use drop nozzles to avoid interference from com leaves and ensure uniform application to the soil. Prowl (pendimethalin) or Treflan (trifluralin) may be applied to the soil and incorporated after field corn is 4 inches high (for Prowl) or 8 inches high (for Treflan) and up to the time of the last cultivation. The field should be cultivated to control existing weeds and cover the roots at the base of the corn before application. The herbicide should then be thoroughly and uniformly in- corporated into the top inch of the soil with a sweep type or rolling cultivator. Prowl may not need incorporation if irrigation or rainfall occurs soon after application. Prowl can be combined with atrazine. These treatments may help control late-emerging grasses such as shattercane, wild proso millet, fall pani- cum, or woolly cupgrass. Lasso (alachlor) may be used alone or with atrazine as a soil-applied postemergence treatment to help control midseason annual grass weeds in com that is grown for seed. Application should preferably be made after culti- vation before weeds emerge and before the crop is 40 inches tall. Directed Postemergence Herbicides Directed sprays are sometimes needed for emergency situations, especially when grass weeds become too tall to be controlled by cultivation. However, weeds are often too large for directed sprays to be effective. Directed sprays cannot be used on small corn because a height difference between com and weeds is needed to keep the spray off the com. Com leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox or Linex (linuron) may be applied as a directed spray after corn is at least 15 inches tall (free standing) but before weeds are 8 inches tall (preferably no more than 5 inches). Linuron controls broadleaf and grass weeds. The broadcast rate is VA to 3 pounds of Lorox 50W (or 50DF) or VA to 3 pints of 4L per acre, depending on weed size and soil type. Add Surfactant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the corn as much as pos- sible. Consider this an emergency treatment. Evik 80W (ametryn) is registered for directed use when corn is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 2'/2 pounds Evik 80 W per acre (broadcast) plus 2 quarts of surfactant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Bladex SOW (cyanazine) or Bladex BOW plus atrazine may be used as a directed spray for lay-by treatment for corn seed production fields at least 60 days before har- vest. Seed com should be at least 10 inches tall and there should be a sufficient height difference between the com and the weeds to allow the spray to cover the weeds but not touch the com leaves. This treatment can control weeds that are up to IY2 inches tall and suppress weeds that are a little taller. The use of nitrogen solutions as carriers and/or the addition of crop oil or surfactant can enhance control. Do not apply over the top of corn. Herbicides for Sorghum Many herbicides used to control weeds in com can also be used in sorghum. Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Ap- plication may be made preemergence or postemergence. A preplant surface application may be made using a single application within 30 days of planting or a % plus \^ split application within 45 days of planting. Plant seed at least 1 inch deep. Do not use preplant or preemergence on soils with less than 1 percent organic matter. Incorpo- rated treatments may cause injury if rainfall occurs prior to or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemer- gence is 2 to 3 pounds of atrazine 80W per acre. The postemergence rate is 4 to 6 pints 4L per acre without crop oil or 2.4 pints 4L (broadleaf control only) with crop oil or crop oil concentrate. Use equivalent rates of atrazine 80W or AAtrex 90DF formulations. Rotational crop recommendations and weed control are the same as for atrazine used in corn. Failure to control fall panicum has been a major problem. Ramrod (propachlor) may be used alone or in com- bination with atrazine, Milogard, Bladex, or Modo\\Ti for sorghum. Ramrod can improve grass control, but rates must not be skimpy, especially on soils that are relatively low in organic matter. For specific rates, con- sult the label. Do not graze or feed forage to dairy animals. Lasso (alachlor) alone or plus atrazine may be pre- plant incorporated or used preemergence for grain sor- ghum if seed is treated with Screen (flurazole). This use also applies to Lasso/a trazine and Bronco (see below). Dual (metolaclilor) or Dual plus atrazine (Bleep) can be used for sorghum if seed has had the Concep- seed treatment. These herbicides will control grasses bet- ter than will atrazine applied alone. An early preplant treatment of Dual or Bleep may be used in a similar manner as for com, but Concep-treated seed should still be used. Basagran (bentazon) is registered for postemergence use in sorghum in a manner similar to that for corn (see corn section) . Since sorghum is quite tolerant of Basa- gran up to and including early boot stage, the addition of a crop oil concentrate is considered relatively safe. Do not apply to grain sorghum that is heading or blooming. Apply Basagran at the rate of 1 to IV2 pints in combina- tion with atrazine at 0.6 to 1.0 pound of SOW, 0.6 to 0.9 pound of 90WDG, or 1 to V/2 pints of 4L per acre. 2,4-D may be applied postemergence for broadleaf control in 4- to 24-inch-tall sorghum. Use drop pipes on nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in com (see section on com herbicides). Banvel can be applied preplant to emerged and ac- tively growing weeds up to 15 days before planting. It may be applied postemergence to sorghum that is be- tween the 3-leaf and 15-inch stage. The 3- to 5-leaf stage is preferred. The rate is V2 pint per acre. Do not graze or feed treated forage or silage prior to the mature grain stage. Sorghum may be injured by Banvel. Brominal or Buctril (bromoxynil) can control broad- leaf weeds in grain sorghum that is past the 3-leaf stage and up to 14 inches tall and before weeds are 4 to 6 inches tall. It is generally safer than 2,4-D on grain sorghum. Combination with atrazine is also registered to improve pigweed control and provide some residual con- trol of germinating seedlings. Prowl (pendimetlialin) may be applied to grain sorghum from the 4-inch growth stage to as late as the last cultivation primarily for control of late-season an- nual grass weeds. See the section entitled "Herbicides for Com," subsection on postemergence soil-applied herbi- cides, for more information. Roundup may be applied as a spot-treatment in sor- ghum (milo) prior to heading. For applications on a spray- to- wet basis use a 1 to 2 percent solution of Roundup in water. For motorized spot treatments where less complete coverage of %veeds may result, use a 5 percent solution. Avoid contact with tlie sorghum. Add a dye for increased visibility. Bronco (glyphosate plus alachlor) may be used alone or with atrazine where grain sorghum is to be planted directly into a cover crop or in previous crop residue. It can control emerged annual weeds and suppress many emerged perennial weeds, as well as give preemergence control. As with Lasso, grain sorghum seed must be treated with Screen, Paraquat may be used for control of annual weeds where grain sorghum is to be planted into previous crop residues. Herbicides for Soybeans Consider the kinds of weeds expected when you select a herbicide program for soybeans, especially when grow- ing soybeans in narrow rows. The herbicide selectivity table (see last page of this guide) lists herbicides and their relative weed control ratings for various weeds. Soybeans may be injured by some herbicides. However, they usually outgrow early injury with little or no effect on yield if stands have not been significantly reduced. Significant yield decreases can result when injury occurs during the bloom to pod fill stages. Excessively shallow planting may increase the risk of injury from some herbi- cides. Accurate rate selection for soil t)'pe is especially essential for Lorox, Linex, Lexone, and Sencor. Do not apply Lorox, Linex, Lexone, Sencor, or Modown after soybeans have begun to emerge. Follow label instructions as to rates, timing, incorporation, and restrictions. For registered combinations, see Table 3. 10 Table 3. — Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Soybeans Amiben Scncor or Lcxone Amiben Lorox + Sencor or or Lexone Linex 1,2 1.2 1.2 PPI only Sonalan 1 1 Treflan 1 1 PPI or Pre Dual 1,2 1,2 Lasso 1,2 1,2 Prowl 1,2 1,2 Surflan* 2 2 1 = Preplant incorporated; 2 = preemergence. — rr Not registered. • Not for preplant incorporation. Prephnf Nof Incorporated Early preplant application can be utilized in many conservation tillage programs such as no-till, ridge-till, or mulch-till to minimize existing vegetation problems at planting and thus reduce the need for knockdown herbi- cides. Lorox or Linex (linuron) and Sencor or Lexone (metribuzin) have both postemergence and residual activity but postemergence activity varies with climatic conditions. If weeds have emerged prior to preplant ap- plication, the use of a foliar knockdown herbicide such as paraquat or Roundup may be necessary. (See No-Till subsection.) Several preemergence herbicides are registered for application prior to planting soybeans. Surflan can be applied anytime prior to planting no-till soybeans. Sur- flan can be applied in fully-tillered wheat before heading, and soybeans can then be planted no-till into wheat before harvest or wheat stubble immediately after harvest. Sur- flan plus Lexone can be applied up to 30 days prior to planting. Prowl can be applied 15 to 30 days prior to planting. Dual can be applied up to 30 days prior to planting soybeans or as a split application using a % rate up to 45 days before planting, followed by a '/s rate at planting. Sencor can be applied with Dual or Lasso 15 to 30 days prior to planting soybeans when using a sequential (split) preemergence application: the first made early followed by the second at planting. Some foliar postemergence herbicides can also be used prior to planting soybeans. Roundup can also be used preplant in soybeans to control small annual weeds. The rate is 12 to 16 fluid ounces (% to 1 pint) per acre in 5 to 10 gallons of water with the addition of a surfactant. Poast may be applied prior to planting soybeans with no time interval restriction. 2,4-D is not registered prior to planting soybeans al- though a registration has been submitted to EPA. Prephnf Incorporation Incorporation is required for Treflan, Sonalan, Ver- nam, and Reward. Incorporation is optional for Amiben, Dual, Lasso, Modown, and Prowl when used alone and in some combinations. Dyanap, Lorox, and Surflan should not be incorporated. Incorporation can improve performance if rainfall is limited and may increase the effectiveness of Dual or Lasso in controlling nutsedge. Incorporation should dis- tribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early application of the herbicide can cause significant reductions in weed con- trol. For more information, see the section entitled "Herbicide Incorporation." Dlnitroaniline herbicides registered for weed control in soybeams are Treflan, Prowl, Sonalan, and Surflan. Treflan and Sonalan should be incorporated because they have low solubility and are subject to loss by vapor- ization and photodecomposition. Incorporation is optional with Prowl, but variable weed control and soybean injury may result if Prowl is not incorporated. Incorpora- tion should distribute the herbicide uniformly in the top 2 to 3 inches of soil (see label for implement settings). Do not incorporate Surflan (see preemergence section). The dlnitroaniline herbicides control annual grasses, pigweed, and lambsquarters and may provide some con- trol of smartweed and annual momingglory. Prowl and Surflan may also partially control velvetleaf. However, acceptable control of most other broadleaf weeds requires combinations or sequentiad treatments with other herbi- cides. Soybeans are sometimes injured by dlnitroaniline herbi- cides. Plants that have been injured by incorporated treatments may be stunted and have swollen hypocotyls and shortened lateral roots. Such injuries are not usually serious. Plants injured by preemergence applications may have stem calluses at the soil surface, which can cause lodging and yield loss. Com, sorghum, and small grains may be injured if they are grown after a soybean crop that has been treated with a dlnitroaniline herbicide. The symptoms are poor germination and stunted, purple plants with poor root systems. To avoid carryover, use no more than the recommended rates and be sure that application and incorporation are uniform. The likelihood of carryover increases with double cropping or late application and after a cool, dry season. Adequate tillage may help dilute herbicide residue to help alleviate a carryover problem. Treflan (trifluralln) can be applied alone anytime in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks prior to planting, and combinations with Amiben, Furloe, or Modown should be applied within a few days prior to planting. Incorpo- rate as soon as possible, but do not delay incorporation more than 24 hours (8 hours if soil is warm and moist). The rate is 1 to 2 pints of Treflan 4E or 5 to 10 pounds of Treflan lOG per acre. Treflan MTF is a multi temper- ature formulation that can be used to avoid problems associated with freezing in storage. Treflan Pro-5 con- tains 5 pounds trifluralln per gallon. 11 Sonalan (ethalfluralin) may be applied up to 3 weeks prior to planting and should be incorporated within 2 days after application. The rate for general weed control ranges from IV2 to 3 pints per acre, depending on soil texture. Sonalan may provide some control of nightshade at rates of 3 to 3Vz pints per acre, but for this purpose it should be used in conjunction with Amiben, Dual, or Lasso or followed with Blazer. Sonalan is less likely to injure com following soybeans than is Treflan. Sonalan may be tank-mixed with Amiben, Lasso, Dual, metri- buzin, or Vemam. Prowl (f>endimethalin) can be applied within 60 days (alone) or 7 days (with Sencor or Lexone) prior to planting soybeans or applied after planting (see pre- emergence section) . Preplant treatments should be in- corporated within 7 days of application. Mechanical in- corporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, al- though rates for combinations with Sencor or Lexone are lower than when the herbicide is used alone. Sencor or Lexone (metribuzin) plus Treflan, Sonalan, or Prowl can be tank-mixed and applied within 7 to 14 days of planting. Incorporate uniformly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is V2 to 1 pint of 4L or V3 to % pound of 75DF. Use the normal rate, or slightly less, of the dinitro- aniline herbicide (see labels) . The application of Sencor or Lexone can also be split, one part being incorporated and the other part applied to the surface preemergence. This method requires two applications but can give better broadleaf control and less injury than incorporating the same total amount of Sen- cor or Lexone in a single application. Amiben (chloramben) can be incorporated with Treflan, Sonalan, or Prowl. The rate is 4 to 6 quarts of Amiben 2S or 2.4 to 3.6 pounds of 75DS per acre. Ami- ben can also be applied and incorporated with Treflan or Prowl plus Sencor or Lexone as a three-way combination. Vemam (vemolate) and Reward 6E (vemolate plus extender) control annual grasses and pigweed. They sometimes provide fair control of annual morningglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vemolate or Reward can be applied within 10 days prior to planting and should be incorpo- rated immediately. The broadcast rate is 2'/3 to 3I/2 pints of Vemam 7E or 20 to 30 pounds of Vernam lOG or 2% to 4 pints Reward 6E per acre. Vernam or Reward plus Treflan is labeled at the rate of 1 pint of Treflan plus 2K3 to 3 pints of Vemam 7E or 2% to 4 pints Reward 6E per acre. The combination may reduce the risk of soy- bean injury. For yellow nutsedge and velvetleaf control use at least 3 pints Vernam 7E or SVz pints Reward 6E per acre. Other labeled combinations include Vernam or Reward plus Amiben, Sonalan, Prowl, Lasso, Furloe, or Treflan/Sencor or Lexone. Preplant or Preemergence Herbicides Lasso (alachlor) or Dual (metolachlor) can be ap- plied to soybeans as a preplant incorporated or pre- emergence treatment. Lasso may be applied within 1 week of planting. Dual may be applied to the soil sur- face early preplant up to 30 days before planting as a single treatment. Or a % rate can be used within 45 days of planting along with a V3 rate at planting. If rainfall is limited, incorporation can improve performance and increase yellow nutsedge control. Soybeans are quite tolerant of Lasso or Dual. The first to second trifoliate leaves often appear crinkled and have a drawstring ef- fect on the middle leaflet, but these symptoms should not cause concern. Lasso or Dual controls annual grasses and pigweed and can help control nutsedge and black nightshade. These herbicides can be combined with Lexone, Sencor, or Amiben (incorporated or preemergence) and with Lorox or Dyanap (preemergence only) to improve broadleaf weed control. The rate for Lasso is 2 to 4 quarts Lasso 4E or Micro- tech 4L or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is V/2 to 3 pints per acre, and the rate for Dual 25G is 6 to 12 pounds per acre. Use the higher amount for the soil when incorporating or when black nightshade or yellow nutsedge are to be controlled. The rate for combinations is slightly less than that for the herbicide used alone (see labels). Lasso may be applied after soybean emergence but before soybeans pass the unifoliate stage. Amiben (chloramben) can control annual grasses and many broadleaf weeds in soybeans when used at the full rate. Do not expect control of cocklebur or annual morn- ingglory. Control of velvedeaf and jimsonweed is often erratic. .Amiben occasionally injures soybeans, but dam- age does not usually affect yield. Injured plants may be stunted and have abnormal, shortened roots. If rain does not occur within 3 to 5 days of an Amiben preemergence application, you should rotary hoe. Amiben is best suited to soils that have over 2.5 percent organic matter. Amiben can be applied alone or with Dual, Lasso, or Prowl as a preplant-incorporated or preemergence treat- ment. Amiben plus Sencor can also be mixed with Lasso, Dual, or Prowl as a preplant or preemergence treat- ment. Amiben can be applied as a preemergence treat- ment with Lorox, Lexone, or Sencor. The Amiben broadcast rate alone is 20 to 30 pounds of lOG, 4 to 6 quarts of 2S, or 2.4 to 3.6 pounds of 75DS per acre. The Amiben rate in combinations is 3 to 6 quarts of 2S (1.8 to 3.6 pounds of 75DS) per acre. Use the higher rate where black nightshade, velvetleaf, or common ragweed is a problem weed. Sencor or Lexone (metribuzin) can be applied any- time during the 1 to 2 weeks prior to planting and in- corporated with Dual, Lasso, Prowl, Sonalan, or Treflan. Incorporation should distribute the herbicide evenly in the top 2 inches of soil. It can be applied preemergence 12 by itself or with Amiben, Dual, Lasso, Prowl, Surflan, or Dyanap. A three way combination of metribuzin plus linuron (Lorox or Linex) plus Lasso or Dual can be applied preemergence. Sencor or Lexone can control many annual broadleaf weeds but cannot control annual momingglory. Control of giant ragweed, jimsonweed, and cocklebur is marginal at the reduced rates necessary to minimize soybean injury. Adjust rates accurately according to soil conditions. Do not apply to very sandy soil. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is V2 to 1 pint of 4L, or V3 to % pound of 75DF. You can use higher amounts as a split preplant and preemergence applica- tion. The higher amounts can improve broadleaf control but also increase the risk of soybean injury. One symptom of soybean injury is yellowing (chlorosis) of the lower leaves at about the first trifoliate stage or later; it may be followed by browning of leaves and death of plants, depending upon the severity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with a pH over 7.5. Accurate, uniform application and incorporation are essential. Some soybean varieties are more sensitive than others. Injury has sometimes occurred when organophosphate insecticides such as Thimet, Counter, Dyfonate, Lorsban, or Mocap were left in applicators used for com planting and were applied to soybeans that were then being treated with metribuzin. Modown (bifenox) can control pigweed, lambsquar- ters, and smartweed and can provide some control of velvetleaf. Modown 4F rates are 2'/2 to 4 pints per acre. Combinations with Dual, Lasso, or Surflan, or an over- lay after Treflan can improve grass control. For preplant incorporation, the application should be made within 2 to 3 days of planting, and incorporation should distribute the herbicides uniformly in the top 1 inch of soil. Do not apply Modown after soybeans begin to emerge. Soybeans may show stunting from Modown, especially from preemergence use followed by cold, wet soil condi- tions during early growth stages. Injury symptoms are cupping and criakling of the first few leaves. Soybean injury is usually not reflected in yield. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan or Vemam; or it can be ap- plied preemergence by itself or with Lasso to improve smartweed control. Preplant application should be done within a few days of planting soybeans, and incorpora- tion should distribute the herbicide uniformly in the top 1 to 2 inches of soil. The rate in sequential or tank mix combinations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preemergence Herbicides Lorox or Linex (linuron) is best suited to silt loam soils that contain 1 to 3 percent organic matter. Do not apply to very sandy soils. Linuron controls broadleaf weeds better than grass weeds. It does not control annual momingglory, and control of cocklebur and jimsonweed is variable. Accurate and uniform application and proper rate selection are necessary to minimize the risk of crop injury. Tank mix combinations allow the use of a reduced rate of linuron to decrease the risk of soybean injury, but may also decrease the degree of weed control. Linuron is registered in tank mix combinations wdth Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of linuron in these combinations is 1 to 1% pounds of linuron 50W or 1 to 1% pints of linuron 4L on silt loam soils that have less than 3 percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if there is adequate rainfall. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after application. Surflan can be used for early preplant application for no- till soybeans. Do not use on soils that have more than 5 percent organic matter. The rate is 1 to 2 poimds per acre of Surflan 75 W (% to V/i quarts AS [aqueous sus- pension]) used alone or % to 1% pounds of Surflan 75W in combinations. Surflan can be tank-mixed with Amiben, Lorox, Lexone, Sencor, or Dyanap to improve broadleaf weed control. Surflan may cause stem callusing, which can lead to soybean lodging. Do not allow Surflan to con- tact the soybean seed. For no-till soybeans, Surflan can be applied in fall or early spring over undisturbed stubble from the previous crop. Prowl can be applied preemergence in combination with Amiben, Lorox, Lexone, or Sencor, When applied to the soil surface. Prowl may cause stem callusing, which can lead to soybean lodging. (See preplant section for more information.) Dyanap (dinoseb plus naptalam) can be applied to soybeans from the time they are planted until the time the unifoliate leaves of the seedling unfold and expose the growing point. Tank mixes of Dyanap plus Lasso, Dual, or Surflan are registered to improve grass control. Dyanap can also be tank-nuxed with Lasso 4E plus Sencor. The Dyanap rate is 4 to 6 quarts per acre for preemergence application. Posfemergence Herbicides Research suggests that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after planting. Postemergence herbicides are most effec- tive when their use is part of a planned program and when they are applied while the weeds are young and tender. They should not be considered simply as emer- gency treatments. It is especially important to use timely treatments when using postemergence herbicides in nar- row-row soybeans. Postemergence herbicides are often the best choice for controlling problem weeds such as cocklebur, annual momingglory, and volunteer corn. Registered combinations are shown in Table 4. For more 13 Table 4. — Registered Postemergence Herbicide Combinations for Broadleaf Weed Control in Soybeans Blazer Butoxone* Butyrac* X X X X X X X X X X Amibcn Alanap X Amiben Basagran — Blazer X Dyanap — X =r Registered. — = Not registered. • 2,4-DB. information on conditions affecting application, see the section entitled "Postemergence Herbicide Principles." Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf. It is weak on pigweed, lambsquarters, and annual morning- glory. It can be used for control of yellow nutsedge and Canada thisde but does not control annual grasses. The suggested rate for Basagran is % to 1 quart per acre, depending on the weed size and species. Application should be made when weeds are small (2-3 inches) and actively growing. These conditions usually exist when the soybeans are in the unifoliate to second trifoliate stage or within 2 to 3 weeks of planting. Spraying during warm sunny weather can also improve performance. Do not spray if rain is expected within 8 hours. Use a minimum of 20 gallons of water per acre and 40 psi spray pressure to get complete weed coverage. Adding a crop oil con- centrate to Basagran may increase performance on most weeds but may cause some soybean injur)'. Momingglory that is up to 10 inches long can be controlled with the addition of 2 fluid ounces of 2,4-DB with Basagran. Do not add crop oil when mixing with 2,4-DB. Do not mix or apply Basagran with other pesticides or liquid fertilizer except as specified on the product label. Basagran may be labeled in 1986 with a 28-0-0 liquid fertilizer adjuvant. Blazer (acliluorfen) should be applied when broad- leaf weeds are in the 2- to 4-inch stage and actively grow- ing. Weeds controlled include annual momingglory, pig- weed, jimsonweed, and black nightshade. Cocklebur and momingglory control can be improved with the addition of 2 fluid ounces of 2,4-DB. Apply the mixture when cocklebur and momingglory measure no more than 10 to 12 inches. The rate is 2 pints of Blazer 2L per acre. Blazer re- quires the addition of a nonionic surfactant at a mini- mum of 1 pint per 100 gallons of spray. The rate of surfactant may be increased to 2 to 4 pints per acre to improve control of small escaped grasses. Surfactant addition is recommended when combining Blazer and 2,4-DB. Since Blazer is a contact herbicide, leaf bum often occurs; however, the crop usually recovers within 2 to 3 weeks. For ground application, use 20 to 40 gallons of water per acre applied with a minimum spray pressure of 40 psi. Do not spray if rain is expected within 6 hours. Basagran plus Blazer provides a means of broadening the spectrum of control. The rate is 1 to 2 pints of each product in the combination. Crop oil concentrate may be added. To improve velvetleaf control with Blazer plus Basagran, 10-34-0 liquid fertilizer can be used at one quart per acre to replace the surfactant or crop oil con- centrate (COC). Do not add COC when using 10-34-0. A mixture of Blazer plus Basagran plus 2 fluid ounces of 2,4-DB can be used to control cocklebur and moming- glory under dry weather conditions. Refer to individual product labels for specifics. Dyanap (dinoseb plus naptalam) at 2 quarts per acre can be applied to soybeans after the first bifoliate leaf is fully expanded until the soybeans become 20 inches tall. After 2 trifoliates are fully expanded, 3 quarts per acre may be used. Dyanap controls cocklebur, jimsonweed, and annual momingglor)'. A split application of 2 quarts at the first to second trifoliate stage, followed by 2 quarts 10 to 14 days later, is suggested for severe weed infestations. The addition of 2 fluid ounces per acre of 2,4-DB can improve control of some of the larger and more difficult weeds, especially if they are over 6 inches tall. Best results are obtained by using high pressure (40 to 60 psi) and 8 to 10 gallons of water per acre. Use 5 gallons of water for aerial application. Although leaf bum can occur, the crop usually recovers within 2 to 3 weeks with little or no yield loss. Do not apply Dyanap to wet soybean foliage or if rain is expected within 6 hours. Do not add a surfactant or crop oil. Amiben (chloraraben) can be used for postemergence application on soybeans in the cracking to fourth tri- foliate stage, but only within 33 days after planting. This treatment can be especially helpful in controlling velvet- leaf, but smartweed, common ragweed, and pigweed may also be controlled or suppressed. Velvetleaf may be 1 to 8 inches tall and smartweed may be 1 to 3 inches tall. For ground applications, 10 to 20 gallons of water per acre, a spray pressure of 30 psi, and flat fan nozzle tips are suggested. The rate of Amiben 2S alone is 6 quarts; it is 5 to 6 quarts per acre in combination with either 2 to 3 fluid ounces of Butyrac 200, 2 to 3 quarts of Alanap, or 1 V2 to 2 pints of Blazer per acre. Crop oil con- centrate should be used at 1 quart per acre with the Amiben alone or tank-mixed with Alanap. Do not add crop oil when tank-mixing with Butyrac. The Amiben plus Alanap or 2,4-DB should be applied when soybeans are in the third to sixth trifoliate stage. Apply the Ami- ben tank-mixed with Blazer at the appropriate rate for the weed size indicated on the Blazer label but within 33 days after planting. If Amiben is also soil-applied, do not use more than a total of 1 2 quarts per season. Rescue (naptalam plus 2,4-DB) can be used for mid- to late-season postemergence control of cocklebur, giant ragweed, and wild sunflower; it may also suppress annual momingglory. Apply 3 quarts per acre after soybeans are about 14 inches tall or after first bloom. Use the lower rate when weeds are less than 12 inches tall. The addi- tion of a crop oil concentrate or surfactant can improve 14 control. Application before the weeds flower is suggested for best control. The water volume per acre is 10 to 25 gallons for ground application and a minimum of 5 gallons for aerial application. If rain occurs within 6 hours, effectiveness may be reduced. Activity may not be very noticeable until 10 to 14 days after application; maximum activity should occur 20 to 30 days after appli- cation. Crop injury such as leaf twisting and terminal droop may occur. To avoid possible yield losses, do not apply Rescue to soybeans under stress from drought, dis- ease, or injury from another herbicide. Do not apply Rescue within 60 days of harvest. Hoelon (diclofop) can control small annual grasses in the 1- to 4-Ieaf stage and volunteer com. Let all the volunteer com emerge, but apply Hoelon before the com that emerged first is too large to obtain adequate spray coverage. For ground application, use a minimum of 20 gallons of water per acre and 40 psi spray pressure. For aerial application, use a minimum of 5 gallons of water per acre. The Hoelon rate for annual grasses, in- cluding volunteer com, is 2 to 3Vi pints. Crop oil con- centrate can be added at 1 to 2 pints per acre. Do not tank-mix Hoelon with other postemergence herbicides. Hoelon is a restricted-use herbicide. Poast (sethoxydim) can be used for postemergence control of annual and perennial grasses in soybeans. The rate is 1 pint per acre to control foxtails or most other annual grasses that are 3 to 18 inches tall or volunteer com or shattercane that is 6 to 18 inches tall. Apply V2 pint per acre when wild proso millet is 4 to 10 inches tall. For control of volunteer cereals, apply IV2 pints per acre before tillering, up to 6 inches tall. Poast is not rec- ommended for spring control of volunteer cereals that emerged the previous fall. Wirestem muhly up to 6 inches tall can usually be controlled by a single applica- tion of VA pints per acre. Poast can also be used as a rescue treatment for controlling selected annual grasses. Apply Poast at a rate of IV2 pints per acre for control of actively growing foxtails or seedling johnsongrass (up to 16 inch height), fall panicum or bamyardgrass (up to 12 inch height) , and crabgrass or goosegrass (up to 8 inch height) . For control of actively growing wild proso millet up to 24 inch height, apply Poast at 1 pint per acre. Use 5 to 20 gallons of spray solution per acre for ground application and a minimum of 5 gallons per acre for aerizil application. Use only standard high pressure hollow cone or flat fan nozzles with pressure at the nozzle adjusted to a minimum of 40 psi and a maximum of 60 psi. Always add crop oil concentrate at 2 pints per acre. Do not cultivate 5 days prior to Poast application or within 7 days following application. Poast can be tank-mixed with Basagran, provided the Poast rate is increased by 50 percent to compensate for the reduced grass control that often occurs with this treatment. Sequential applications at least 24 hours apart may be more economical and practical, depending upon the weeds to be controlled and their size. Do not apply Poast if rainfall is expected within 1 hour. Do not apply Poast to grasses under stress from hot, dry weather or herbicide injury. Blazer may be tank mixed with Poast (Blazer label) for postemergence control of broadleaf and annual grasses in soybeans. The rate per acre is V/2 to 2 pints of Blazer plus 1 pint of Poast plus 2 pints of crop oil con- centrate for fall panicum and giant foxtail that are 3 to 8 inches tall. For other annual grasses on the Poast label increase the rate of Poast by 50 percent. Sequential applications should always be used in place of the tank mixtures for perennials and may be more economical for many annuals. Fusilade 2000 (fluazifop) can be used for postemer- gence control of annual and perennial grass weeds in soybeans. Apply only to actively growing grasses before they tiller. The rate is l'/2 pints per acre when giant fox- tail is 2 to 6 inches tall and other annual grass weeds are 2 to 4 inches tall. Use Vi pint per acre when volun- teer com is 12 to 24 inches tall, shattercane is 6 to 12 inches tall, or wild proso millet is 6 to 12 inches tall. For control of volunteer cereals, apply 1 pint per acre before plants are 2 to 6 inches tall. To control wirestem muhly, apply V/2 pint per acre when plants are 4 to 12- inches tall. Fusilade can also control johnsongrass and quack- grass (see specific weed section), but sequential applica- tions may be needed. The spray volume should be a minimum of 10 gallons per acre for ground application and 5 gallons per acre for aerial application. Add either crop oil concentrate at 1 percent by volume (1 gallon per 100 gallons of spray) or a nonionic surfactant at Vi percent of spray volume. For aerial application add 1 pint of crop oil concentrate or surfactant per acre. Apply before soybeans bloom. Do not tank-mix Fusilade with other postemergence herbicides intended for control of broadleaf weeds except as speci- fied. A tank mix of Fusilade 4E and Blazer 2L is labeled for use without an increase in the Fusilade rate. Roundup (glyphosate) can be applied through several types of selective applicators — recirculating sprayers, wipers, or rope wicks. This application is particularly useful for control of volunteer com, shattercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be at least 6 inches above the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soy- beans. For equipment calibration, refer to the Roundup label. For recirculating sprayers and wipers, use the rates given on the label. For rope-wick applicators, mix 1 gallon of Roimdup in 2 gallons of water. A spot treat- ment with Roundup is also a good option in many fields. For application made on a spray-to-wet basis, use a 1 to 2 percent solution of Roundup in water. For motorized spot treatments where less than complete coverage of weeds may result, use a 5 percent solution. Avoid contact of the spray with the soybeans. Add a dye for increased visibility. 15 Paraquat Harvest Aid Paraquat and Gramoxone are registered for drying weeds in soybeans just before harvest. For indeterminate varieties (most Illinois varieties) , apply when 65 percent of the seed pods ha\e reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when at least one-half of the leaves have dropped and the rest of the leaves are turning yellow. The rate is Vi to 1 pint of Paraquat or Gramoxone per acre. Tlie higher rate is for cocklebur. The total spray volume per acre is 2 to 5 gallons for aerial application and 20 to 40 gallons for ground application. Add 1 quart of nonionic surfactant per 100 gallons of spray. Do not pasture li\estock within 15 days of treatment, and remove li\-estock from treated fields at least 30 days before slaughter. Specific Weed Problems Yellow Nutsedge Yellow nutsedge is a perennial sedge with a triangular stem. It reproduces mainly by tubers. Yello\v nutsedge tubers begin sprouting about May 1 in central Illinois. For tlie most efTective control, soil-applied herbicides should be incorporated into the top 2 inches of the soil. For soybeans, a delay in planting until late May al- lows time for two or three tillage operations to destroy many nutsedge sprouts. These operations help deplete food reserves in nutsedge tubers. Row cultivation is help- ful. Preplant applications of Lasso, Dual, Vernam, or Reward wall also help. Lasso (alachlor) preplant incorporated at 2V2 to 4 quarts per acre can often give good control of nutsedge. Dual (metolachlor) can be applied at 2 to 3 pints per acre to control nutsedge. Preplant incorporated treatment is preferred to treatment at the preemergence stage. Vernam 7E (vemolate) applied preplant at SVi pints per acre is also effective against yellow nutsedge. Reward 6E at 4 pints per acre is an alternative to Vernam. Im- mediate incorporation is necessary with Vernam or Reward. Basagran (bentazon) applied postemergence can also help control nutsedge in soybeans. WTien nutsedge is 6 to 8 inches tall, ^4 to 1 quart per acre can be applied. If needed, a second application can be made 7 to 10 days later. The addition of a crop oil concentrate to Basagran may improve performance. For com that is planted relatively early, preplant tillage before nutsedge sprouts is of little help in control. Timely cultivation gives some control, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane Extra at 2% to 4 quarts or Eradicane, Sutan+, or Genate Plus at 4',4 to 7Vi pints per acre are effective for control of yellow nutsedge in com. They must be incor- porated immediately. Lasso or Dual applied in corn as for soybeans can also be quite effective. The combinations of Lasso, Dual, Sutan+, Genate Plus or Eradicane incoi-porated with atrazine may im- prove control of nutsedge while also controlling broad- leaf weeds. Atrazine or Bladex (cyanazine) can be used as a post- emergence spray to control emerged yellow nutsedge when it is small. Split applications of atrazine plus oil have been more effective tlian single applications. Basa- gran can be used in corn in a manner similar to that for soybeans. Lorox or Linex (linuron) directed postemer- gence spray has also given some control. Jobnsongrass Johnsongrass can reproduce both from seeds and by rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the johnson- grass head begins to appear. Mowing, grazing, or culti- vating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, making them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or suppressed with the use of certain herbicides in various cropping programs. Several herbicides can proxide control of johnsongrass seedlings in soybeans or com (see the table at the end of this publication) . Treflan (trifluralin) or Prowl (pendlmethalin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnsongrass. They are used at V/2 to 2 times the normal rate each year for 2 years ; in the third year, either they are used at the normal rate, or an- other suitable herbicide is used before a regular cropping sequence is resumed. Thorough preplant tillage and in- corporation are necessar)' for satisfactory control. Be certain not to plant crops such as com or sorghum the year following application of these herbicides at the higher rates. Fusilade 2000 (fluazifop) can control johnsongrass in soybeans. Apply IV2 pints per acre ^vhen the weed is 8 to 18 inches tall. Apply before the boot stage of growth. If new shoots or regrowth occur, make a second application of 1 pint per acre when johnsongrass is 6 to 12 inches tall. Always add crop oil concentrate at 1 percent of volume or nonionic surfactant at 0.25 percent of volume. Poast (sethoxydim) can control johnsongrass in soy- beans. Apply l'/2 pints plus 1 quart crop oil concentrate per acre when the johnsongrass is 15 to 25 inches tall. If regrowth or new growth occurs, apply 1 pint p>er acre when the johnsongrass is 6 to 12 inches tall. Eradicane Extra can help control rhizome johnson- grass in com when used at a rate of 4 quarts per acre 16 with a tillage program; or Eradicane 6.7E can be used at IVi pints per acre. Roundup (glyphosate) can be used as a spot treat- ment to control johnsongrass in com, soybeans, or sor- ghum. Apply a 1 percent solution when johnsongrass has reached the boot to head stage and is actively growing. Use of Roundup in rope-wick applicators or recovery- type sprayers is effective for control of johnsongrass in soybeans. (See section on postemergence herbicides for soybeans.) Roundup may be applied in small grain stubble when johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass is a perennial grass with shallow rhizomes. It is found primarily in the northern part of Illinois. Atrazlne is quite effective when used as a split appli- cation in corn. Apply 2 quarts of atrazine 4L per acre in the fall or spring and plow 1 to 3 weeks later. Another 2 quarts per acre should be applied as a preplant or pre- emergence treatment. Postemergence application is usu- ally less effective. A single treatment with 3 to 4 quarts per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. Use equivalent rates of other formulations. If more than 3 pounds of atrazine active ingredient is applied per acre, plant no crops other than corn or sorghum the next year. Eradicane Extra can be used to suppress quackgrass in com where more flexibility in cropping sequence is desired. A rate of 2% quarts per acre of Eradicane Extra can be used on light infestations, while 4 quarts per acre is suggested for heavier infestations. There is some risk of com injury, especially at the higher rate. A tank mix with atrazine should improve control. If Eradicane 6.7E is used, the rate should range from 4% to 7^3 pints per acre. Fusilade 2000 (fluazifop) may be used for quackgrass control in soybeans at XVi pints per acre. Apply when quackgrass is 6 to 10 inches tall. If rcgrowth occurs, a second application of 1 pint per acre may be made. Best results are obtained with Fusilade and most other treat- ments if rhizomes are cut up by preplant tillage to stimu- late maximum emergence of grass shoots. Always add crop oil concentrate or nonionic surfactant to Fusilade. Poast (sethoxydim) can be applied in soybeans at the rate of 2V2 pints plus 1 quart of crop oil concentrate per acre when quackgrass is 6 to 8 inches tall. If regrowth occurs or new plants emerge, apply Vh pints per acre when the quackgrass is 6 to 8 inches high. Roundup (glyphosate) can be used for controlling quackgrass before planting corn, sorghum, or soybeans. Apply 1 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). For annual cropping systems apply 1 quart per acre in 5 to 10 gallons of spray with surfactant added. Delay tillage for 3 or more days after application. W/resfem Mubly Wirestem muhly occurs primarily as a problem in northern and western Illinois. It is a perennial which reproduces by seeds and scaly rhizomes. These rhizomes are often moved by chisel plows, field cultivators, and shovel cultivators. Many farmers report that delayed seedbed preparation, where possible, can provide some control of wirestem muhly. However, wirestem muhly does not start growth until late in the spring. Roundup can be used early preplant (early June) or post-harvest when wirestem muhly is at least 8 inches tall and actively growing. Do not fall or spring till before applications. The rate is 1 quart of Roundup in 5 to 10 gallons of water per acre with surfactant added at 2 to 4 quarts per 100 gallons. Use flat fan nozzles. Wait 3 days before tillage after application. Atrazine at high rates can provide some control of wirestem muhly in corn. Rates must be at highest labeled rates for the soil (see Quackgrass section) . Fusilade can be used postemergence to control wire- stem muhly in soybeans. The rate is IV2 pints per acre when wirestem muhly plants are 4 to 12 inches. Poast can also be used postemergence in soybeans to control wirestem muhly which is 6 inches tall. The rate is l'/2 pints per acre. See Soybean Postemergence section for more information on Poast and Fusilade. Canada Thistle Canada thistle is a perennial weed that has large food reserves in its root system. TTiere are several varieties of Canada thistle. They differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in corn. Banvel (dicamba) often is a little more effective than 2,4-D and may be used alone or in combination wath 2,4-D. Banvel can be used as an after-harvest treatment in wheat, com, or soybean fields or in fallow fields. Rates vary from 1 to 2 quarts of Banvel alone or in tank-mix combinations with 2,4-D or Roundup. Fall treatments should be applied before killing frosts. For best results thistles should be fully emerged and actively growing. Fields treated in the fall with Banvel may be planted to corn, sorghum, or wheat the next season. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in com. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Can- ada thistle in soybeans or com when the thistles are 8 to 12 inches tall. Apply V* to 1 quart per acre in a single application, or for better control make two applications of % to 1 quart per acre each, 7 to 10 days apart. 17 Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow 3 or more days after application before tillage. Black Nightshade Black nightshade has become an increasing problem for Illinois soybean growers. The berries are about the same size as soybeans at harv-est. They contain a sticky juice that can gum up a combine. Black nightshade can be controlled easier in com than in soybeans. Herbicides such as atrazine, Bladex, Banvel, Lasso, and Dual are helpful for controlling this weed in com. If possible, plant suspect fields to corn rather than to soybeans. If soybeans must be planted, plant suspect fields last. Precmergence applications usually maintain control longer than those that are preplant incorporated. For control in soybeans, Lasso, Dual, Amiben, or linuron at full rates or a combination of Amiben or linuron with Lasso or Dual is helpful. Suspect fields should be monitored and a postemergence application of Blazer considered. Blazer 2L at 2 pints per acre can con- trol nightshade when applied at the 2- to 4-leaf stage. Harvest-aid sprays generally do not solve the problem because they do not make the berries fall before the soy- beans are harvested. Additional Information Not all herbicides and herbicide combinations avail- able are mentioned in this publication. Some are rela- tively new and are still being tested. Some are not con- sidered to be well adapted to Illinois or are not used very extensively. For further information on field crop weed control, consult your county extension adviser or write to the Department of Agronomy, N-305 Turner Hall, University of Illinois at Urbana-Champaign, 1102 S. Gk)odwin Avenue, Urbana, Illinois 61801. 18 Relative Effectiveness of Herbicides on Major Weeds This chart gives a general comparative rating. Under unfavorable conditions, come herbicides rated good or fair may give erratic or poor re- sults. Under very favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when se- lecting herbicides. Rate of herbicide used also will influence results. G = good, F = fair or variable, and P = poor. Grasses Broadleaf Weeds « bo u O § ° § ca M ^ EPS « 2-p rt S J3 nCO rs S -g -C ""5 V bo To t>0 .5 3 O 3 IS u c o 3 .M ^ bo I '5) •a i I «3 •^ I 3 1 SOYBEANS Preplant Treflan, Sonalan F-G Scncor, Lexone + dinitroaniline F Vemam, Reward F G G G G G G G G G F P G P-F F P-F P P G P-F G F F F-G G P G P-F P P F P G G P P-F G P F P F-G F Preplant or Preemergence Amiben Lasso, Dual Lasso or Dual + Sencor or Lexone Lasso or Dual + Lorox,* Linex' Lorox,* Linex* Sencor, Lexone Surflan.' Prowl F-G G F F F F-G G G G F F F-G F-G F-G F G G G P-F G F F G F F G F F P P P F-G P-F P P P P P P P-F P F-G P F F P F F P F F-G P-F P P G F G G G G F-G G F-G G F-G G F-G G F G P G P G F-G P-F G G G P F F F P F-G P-F G G G P-F F F F P F P F-G F-G F-G F-G P-F Postemergenc* Basagran Blazer Dyanap 2,4-DB Poast, Fusilade Rescue F-G F F P-F G F-G P P-F P P G P P P P P G P P P-F P P G P P P P P G P P P P P G P P P P P G P P-F G G F-P P G F G F-P F-G F-G G G F P-F F-G G P-F F P P P P P P G F F P P-F P F-G F-G F-G G F F P-F F F P P P P PGP F F F P G F-G P P P P P CORN Preplant Butylate, EPTC Butylate, EPTC + atrazinc, Bladex Princep + atrazine F-G G G G G F-G F-G F-G G G G G F-G F-G G F-G F-G F F P-F P F-G F-G G F-G F-G G P-F G G G G G G G G F G G G P F F-G F-G G F Preplant or Preemergenc* (\trazine G Bladex F-G Bladex + atrazinc F-G Lasso, Dual F-G Lasso or Dual 4" atrazine or Bladex F-G Prowl + atrazine or Bladex" F Ramrod' G F-G F P P P F-G F-G F-G G P F-G F F F-G P G G G G P-F G G G G F F-G G F F P P F-G F-G P P-F G F-G G F F-G G F-G F-G G P P P F-G F F-G F P P G P G G G F G F G G G G G G F-G G F G F-G G F-G F-G G G G F-G G F-G F-G F-G G P-F P P-F P P G G G PGP F P G F-G F G F-G F-G P P P Postern ergence Atrazine + oil Banvel Basagran Bladex Buctril, Brominal 2,4-D F-G F-G G F-G F-G F F-G P P G P P G P P G P P P P P F P P P P P F-G P P F P F F P P G G P-F F G G G G G F-G G G G G G G G F G G F-P F G G G G G P P G F-G G F G G F G G F G F F F G G G G G P-F G G G F F-G G F F-G F-G F F-G Do not use for preplant incorporation. Prepared by M. D. McGlamery, Professor of Weed Science, Ellery L Knake, Professor of Weed Science. Dave R. Pilce, Associate Agronomist and C. D.ane Anderson, Extension Assistant, all at the University of Illinois; with the assistance of Fred W. Slife, Emeritus Professor of Agronomy at the Uni- versity of lllmois, George Kapusta. Professor of Plant and Soil Science, Southern Illinois University, Carbondale, and Gordon Roskamp Associate Professor of Agriculture, Western Illinois University. This guide is based in part upon research conducted by Loyd M. Wax, Agronomist USDA and Professor of Weed Science, and E. W. Stoller, Plant Physiologist, USDA, and Professor of Agronomy, both at the University of Illinois. The assis'fance of industry representatives is also gratefully acknowledged. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30 1914 in cooperation with the U.S. Department of Agriculture. WILLIAM R. OSCHWALD, Director, Cooperative Extension Service, University of Illinois at Urbano-Champaign. The Illinois Cooperative Extension Service provides equal opportunities in programs and employment. ISM— 10-85— 62799— ct .i32.954 R77 1987 1^ UX mmsiTY OF liums /AGRICULTURE imm 1987 Row Crop Weed Control m vmm of the MAR 2 5 1987 or \\\m\ This guide is based on the results of research conducted by the University of Illinois Agricultural Experiment Station, other experinaent stations, and the United States Department of Agriculture (USDA). Consider- ation has been given to the soils, crops, and weed problems of Illinois. The effectiveness of herbicides is influenced by rainfall, soil factors, weed spectrum, method of ap- plication, and formulation. Under certain conditions, some herbicides may damage the crop to which they are applied. In some cases, herbicide residues in the soil may damage crops that are grown later; and some herbicides may move outside the target area, affecting desirable plants. Precautions When selecting a herbicide, consider both the risk involved in using the herbicide and the yield losses caused by weeds. You can reduce risks by taking the following precautions: • Apply herbicides only to those crops for which use has been approved. • Clean tanks thoroughly when changing herbicides, especially when ustng a postemergence herbicide. Use a 1 -percent ammonia wash to clean out traces of 2,4-D or dicamba from the tank before spraying soybeans. Note that some herbicide labels provide cleaning suggestions. • Correctly calibrate the sprayer and check the nozzle output and adjustment before adding herbicide to a tank. • Use recommended rates. Applying too much herbi- cide is costly and, in addition, may damage crops and cause illegal residues. Using too little herbicide can result in poor weed control. • Apply herbicides only at times specified on the label. Observe the recommended intervals between treat- ment and pasturing or harvesting of crops, as well as recommended intervals between application and subsequent planting of crops. • Wear goggles, rubber gloves, and other protective clothing as suggested by the label. • Guard against drift injury to nearby susceptible plants, such as ornamentals and vegetables, as well as agronomic crops. Mist or vapors from 2,4-D and dicamba sprays may drift several hundred yards. Whenever possible, operate sprayers at low pressure with tips that deliver large droplets. Spray only on calm days or make sure that the wind is not moving toward susceptible crop plants and ornamentals. Use special precaution with Command. • Apply herbicides only when all animals and persons not directly involved in the application have been removed from the area. Avoid unnecessary exposure. • Check the label for the proper method of container disposal. Triple rinse, puncture, and haul metal con- tainers to an approved sanitary landfill. Haul paper containers to a sanitary landfill or bum them in an approved manner. • Promptly return unused herbicides to a safe storage place. Store them in the original containers away from unauthorized persons, particularly children. • Because formulations and labels are sometimes changed and government regulations modified, al- ways refer to the most recent product label. This guide has been developed to help you use herbicides as effectively and safely as possible. Because no guide can remove all the risk involved, however, the University of Illinois and its employees assume no responsibility for the results of using herbicides, even if they have been used according to the suggestions, recommendations, or directions of the manufacturer or any governmental agency. Cultural and mechanical control Good cultural practices that aid in weed control include adequate seedbed preparation, adequate fer- tilization, crop rotation, planting on the proper date, use of the optimum row width, and seeding at the rate required for optimum stands. Planting in relatively warm soil helps crops compete better with weeds. Good weed control during the first 3 to 5 weeks is extremely important for both com and soybeans. If weed control is adequate during that period, com and soybeans will usually compete quite well with most of the weeds that begin growing later. Narrow rows will shade the centers faster and help the crop compete better with the weeds. If herbicides alone cannot give adequate weed control, however, then keep rows wide enough to allow for cultivation. Some of the newer herbicides are improving the chances of achieving adequate control without cultivation. If a preemergence or preplant herbicide does not appear to be controlling weeds adequately, use the rotary hoe while weeds are still small enough to be controlled. Use the rotary hoe after weed seeds have germinated but before most weeds have emerged. Operate it at 8 to 12 miles per hour and weight it enough to stir the soil and kill the tiny weeds. Rotary hoeing also aids crop emergence if the soil is crusted. Row cultivators also should be used while weeds are small. Throwing soil into the row can help smother small weeds. Cultivate shallowly to prevent injury to crop roots. Herbicides can provide a convenient and economical means of early weed control and allow for delayed and faster cultivation. Furthermore, unless the soil is crusted, it may not be necessary to cultivate some fields at all if herbicides are controlling weeds ade- quately. Herbicide incorporation Soil-applied herbicides are incorporated to minimize surface loss, reduce dependence upon rainfall, and provide appropriate placement of the herbicide. Her- bicides such as Sutan-t- and Eradicane are incorporated soon after application to minimize surface loss from volatilization. Treflan and Sonalan are incorporated within a few hours to minimize loss due to photode- composition and volatilization. Triazine herbicides such as atrazine and Bladex and acetamide herbicides such as Lasso and Dual may be incorporated to minimize dependence upon timely rainfall; but because these herbicides are not lost as quickly from the soil surface, the timing of incorporation is less critical. Incorporation should place the herbicide uniformly throughout the top 1 or 2 inches of soil for best control of small-seeded annual weeds that germinate at shal- low depths. Slightly deeper placement may improve the control of certain weeds from deep-germinating seed under relatively dry conditions. Incorporating too deeply, however, tends to dilute the herbicide and may reduce the effectiveness. The field cultivator and tan- dem disk place most of the herbicide at about one- half the depth of operation. Thus for most herbicides, the suggested depth of operation is 3 to 4 inches. Thorough incorporation with ground-driven imple- ments requires two passes. Single-pass incorporation can result in streaked weed control, especially in moist soils. Single-pass incorporation may be adequate with some herbicides that tend to move laterally in the soil. It may also be adequate with some equipment, espe- cially if rotary hoeing, cultivation, or subsequent her- bicide treatments are used to improve weed control. If the first pass sufficiently covers the herbicide to prevent surface loss, the second pass can be delayed until immediately before planting. The depth and thoroughness of incorporation de- pend upon the type of equipment used, the depth and speed of operation, the texture of the soil, and the amount of soil moisture. Field cultivators and tandem disks are commonly used for incorporation; however, disk-chisels and other combination tools are being used in some areas. Field cultivators Field cultivators are frequently used for herbicide incorporation. They should have three or more rows of shanks with an effective shank spacing of no more than 8 to 9 inches (a spacing of 24 to 27 inches on each of three rows). The shanks can be equipped with points or sweeps. Sweeps usually give better incor- poration, especially when soil conditions are a little too wet or dry for optimum soil flow and mixing. Sweeps for "C" shank cultivators should be at least as wide as the effective shank spacing. The recommended operating depth for the field cultivator is 3 to 4 inches. It is usually sufficient to operate the field cultivator only deep enough to remove tractor tire depressions. The ground speed should be at least 6 miles per hour. The field cultivator must be operated in a level position so that the back shanks are not operating in untreated soil, which would result in streaked weed control. Two passes are recommended to obtain uniform weed control. If single-pass incor- poration is preferred, the use of wider sweeps or narrower spacing with a 3- to 5 -bar harrow or rolling baskets pulled behind will increase the probability of obtaining adequate weed control. Tandem disks Tandem disk harrows invert the soil and usually place the herbicide deeper in the soil than most other incorporation tools. Tandem disks used for herbicide incorporation should have disk blade diameters of 20 inches or less and blade spacings of 7 to 9 inches. Larger disks are considered primary tillage tools and should not be used for incorporating herbicides. Spher- ical disk blades give better herbicide mixing than do conical disk blades. Tandem disks usually place most of the herbicide in the top 50 to 60 percent of the operating depth. For most herbicides, the suggested operating depth is from 3 to 4 inches. Two passes are recommended to obtain uniform mixing with a double disk. A leveling device (harrow or rolling baskets) should be used behind the disk to obtain proper mixing. Recom- mended ground speeds are usually between 4 and 6 miles per hour. The speed should be sufficient to move the soil the full width of the blade spacing. Lower speeds can result in herbicide streaking. Combination tools Several new tillage tools combine disk gangs, field cultivator shanks, and leveling devices. Many of these combination tools can handle large amounts of surface residue without clogging and yet leave considerable crop residue on the soil surface for erosion control. Results indicate that these combination tools may provide more uniform one-pass incorporation than does a disk or field cultivator, but one pass with them is generally no better than two passes with the disk or field cultivator. Chemical weed control Plan your weed-control program to fit your soils, tillage program, crops, weed problems, and farming operations. Good herbicide performance depends on the weather and on wise selection and application. Your decisions about herbicide use should be based on the nature and seriousness of your weed problems. The herbicide selectivity tables at the end of this guide indicate the susceptibility of our most common weed species to herbicides. Corn or soybeans may occasionally be injured by some of the herbicides registered for use on those crops. To reduce injury to crops, apply the herbicide uniformly, at the time specified on the label, and at the correct rate. (See the section entitled "Herbicide rates.") Crop tolerance ratings for various herbicides are also given in the tables at the end of this guide. Unfavorable conditions such as cool, wet weather, delayed crop emergence, deep planting, seedling dis- eases, soil in poor physical condition, and poor-quality seed may contribute to crop stress and herbicide injury. Hybrids and varieties also vary in their tolerance to herbicides and environmental stress factors. Once in- jured by a herbicide, plants are prone to disease. Crop planting intentions for next season must also be considered. Where atrazine or simazine is used, you should not plant spring-seeded small grains, small- seeded legumes and grasses, or vegetables the follow- ing year. Be sure that the application of Treflan or similar herbicides for soybeans is uniform and suffi- ciently early to reduce the risk of injury to wheat or corn following soybeans. Note that certain cropping restrictions apply for Command, Scepter, Classic, Pre- view, and Lorox Plus. Refer to the herbicide label for information about cropping sequence and appropriate intervals to allow between different crops. Names of some herbicides Trade Common (generic) AAtrex, Atrazine atrazine Amiben chloramben Banvel dicamba Basagran bentazon Bicep metolachlor plus atrazine Bladex cyanazine Blazer, Tackle adfluorfen Bronco alachlor plus glyphosate Buctril, Brominal bromoxynil Butoxone, Butyrac 2,4-DB Classic chlorimuron ethyl Command FMC 57020 Conquest cyanazine plus atrazine Dowpon M dalapon Dual metolachlor Eradicane EPTC plus safener Eradicane Extra EPTC plus safener and extender Evik ametryn Extrazine cyanazine plus atrazine Furloe Chloro IPC chlorpropham Fusilade 2000 fluazifop Gramoxone paraquat Hoelon diclofop Laddok bentazon plus atrazine Lasso alachlor Lorox, Linex linuron Lorox Plus chlorimuron ethyl plus linuron Marksman dicamba plus atrazine Modown bifenox Poast sethoxydim Preview chlorimuron ethyl plus metribuzin Princep, Simazine, Caliber 90 simazine Prowl pendimethalin Ramrod propachlor Rescue naptalam plus 2,4-DB Reward vemolate plus extender Roundup glyphosate Scepter imazaguin Sencor, Lexone metribuzin (several) 2,4-D Sonalan ethalfluralin Surflan oryzalin 3 Sutan+, Genate Plus butylate plus safener Sutazine, Rhino butylate plus atrazine Tandem tridiphane Treflan trifluralin Turbo metribuzin plus metolachlor Vemam vemolate Some herbicides have different formulations and concentrations under the same trade name. No en- dorsement of any trade name is implied, nor is discrim- ination against similar products intended. Herbicide combinations Herbicides are often combined to control more weed species, reduce carryover, or reduce crop injury. Some combinations are sold as a "package nux," while others are tank-mixed. Tank-mixing allows you to adjust the ratio to fit local weed and soil conditions. If you use a tank-mix, you must follow restrictions on all products used in the combination. Problems sometimes occur when mixing emulsifi- able concentrate (EC) formulations with wettable pow- der (WP), water-dispersible hquid (WDL), or water- dispersible granule (WDG) formulations. These prob- lems can sometimes be prevented by using proper mixing procedures. Fill tanks at least one-third full with water or liquid fertilizer before adding herbicides that are suspended. If using liquid fertilizers, check compatibility in a small lot before mixing a tankful. The addition of compatibility agents may be necessary. Wettable powders, WDGs, or WDLs should be added to the tank and thoroughly mixed before adding ECs. Emulsify ECs by mixing with equal volumes of water before adding them to the tank. Empty and clean spray tanks often enough to prevent accumulation of material on the sides and the bottom of the tank. The user can apply two treatments of the same herbicide (split application) or use two different her- bicides, provided such uses are registered. The use of one herbicide after another is referred to as a sequential or overlay treatment. Sequential treatment can be done in a number of ways. For example, a preplant apph- cation may be followed by a preemergence application, or a soil-apphed treatment may be followed by a postemergence treatment. One herbicide may be broadcast, while the other is banded or directed. Herbicide rates Herbicide rates vary according to the time of ap- plication, soil conditions, the tillage system used, and the seriousness of the weed infestation. Sometimes lower rates are specified for preemergence apphcation than for preplant incorporated application. Post- emergence rates may be lower than preemergence rates if the herbicides can be applied at either time. Postemergence rates often vary depending upon the size and species of the weeds and whether or not an adjuvant is specified. Rates for combinations are usu- ally lower than rates for herbicides used alone. The rates for soil-applied herbicides usually vary with the texture of the soil and the amount of organic matter the soil contains. For instance, light-colored, medium-textured soils with little organic matter require relatively lower rates of most herbicides than do dark- colored, fine-textured soils with medium to high organic-matter content. For sandy soils the herbicide label may specify "do not use," "use a reduced rate," or "use a postemergence rather than soil-applied her- bicide," depending on the herbicide and its adaptation and on crop tolerance. The rates given in this guide are, unless otherwise specified, broadcast rates for the amount of formulated product. If you plan to band or direct herbicides, adjust the amount per crop acre according to the percentage of the area actually treated. Many herbicides have several formulations with different concentrations of active ingredient. Be sure to read the label and make the necessary adjustments when changing formula- tions. Postemergence herbicide principles Postemergence herbicides appUed to growing weeds generally have foliar rather than soil action; however, some may have both. The rates and timing of appli- cations are based on weed size and climatic conditions. Weeds can usually be controlled with a lower appli- cation rate when they are small and tender. Larger weeds often require a higher herbicide rate or the addition of a spray additive, especially if the weeds have developed under droughty conditions. Herbicide penetration and action are usually greater when the temperature and relative humidity are high. Rainfall occurring too soon after application (1 to 8 hours, depending on the herbicide) can cause poor weed control. Translocated herbicides can be effective with partial foliar coverage, whereas contact herbicides require more complete coverage. Foliar coverage increases as water volume and spray pressure are increased. Spray nozzles that produce small droplets also improve cov- erage. For contact herbicides, 20 to 40 gallons of water per acre are often recommended for ground application and a minimum of 5 gallons per acre for aerial appli- cation. Spray pressures of 30 to 50 psi are often suggested with flat-fan or hollow-cone nozzles to produce small droplets and improve canopy penetra- tion. These small droplets are quite subject to drift. The use of an adjuvant such as a surfactant, crop- oil concentrate, or fertilizer solution may be recom- mended to improve spray coverage and herbicide uptake. These spray additives will usually improve weed control but may increase crop injury. Spray additives may be needed, especially under droughty conditions or on larger weeds. Crop size limitations may be specified on the label to minimize crop injury and maximize weed control. If weeds are smaller than the crop, basal-directed sprays may minimize crop injury because they place more herbicide on the weeds than on the crop. If the weeds are taller than the crop, rope-wick applicators or recirculating sprayers can be used to place the herbicide on the top of the weeds and minimize contact with the crop. Follow the label directions and precau- tions for each herbicide. Conservation tillage and weed control Conservation tillage refers to tillage methods that provide efficient crop production along with adequate control of soil erosion caused by wind and water. Erosion is controlled by protecting the soil surface with plant residue. The amount of tillage is less than that used in conventional moldboard plowing. Chisel plowing, ridge tilling, or no tillage can be used; several other systems are also available. With reduced tillage systems, there is often a greater reliance upon herbicides for weed control. With these systems, herbicides cannot be incorporated without covering much of the residue that is necessary for effective erosion control. The early application of pre- plant, preemergence, and postemergence herbicides is an alternative to incorporation. Early preplant herbicides may be applied several weeks before planting. Early application may reduce the need for a contact herbicide at planting. However, early preplant application may require additional her- bicides (preemergence or postemergence) or cultivation for satisfactory weed control. Compared with preplant incorporated herbicides, preemergence herbicides require less tillage, but their performance is more dependent upon timely rainfall. Preemergence herbicides, however, have performed better than herbicides that are poorly incorporated. With conservation tillage, a higher application rate of surface-applied herbicides may be required for satis- factory weed control, especially in fields with consid- erable weed infestation or crop residue. Do not, how- ever, use a higher rate than that stated on the label. Use great care when selecting herbicides and choosing application rates. The use of effective postemergence herbicides, which depend upon foliar rather than soil action, may be a logical choice with some conservation tillage systems. No-till and double-crop Com, sorghum, and soybeans can be planted with- out seedbed preparation, either in last year's crop residue (no-till) or as a second crop after a small-grain harvest or forage removal (double-crop). Because it conserves soil, soil moisture, and time, no-till planting has greatly improved the probability of success with double-cropping. Several precautions should be observed in no-till cropping systems. Crop seed should be planted to the proper depth and adequately covered to avoid possible contact with herbicide sprays. (Several herbicide labels give the planting depths that are necessary to avoid possible injury.) Preemergence applications may give better weed control than preplant applications because the planting process may expose untreated soil that contains viable weed seed. The total reliance on chem- ical weed control and the large amounts of crop residue present under no-till cropping systems may require that the higher labeled herbicide rates be used to obtain acceptable weed control. Control of existing vegetation in reduced tillage programs Existing vegetation may be a perennial grass sod, a legume or legume-grass sod, an annual cover crop, or weeds. Perennial legume sods can often be controlled prior to planting com or sorghum by preplant appli- cations of 2,4-D or Banvel. Applications in the fall or relatively early in the spring may help to reduce risk of injury to the crop. Perennial grass sods can some- times be controlled v^th preplant applications of Roundup. If a cutting of forages such as alfalfa or clover is removed before no-till planting, control of sod may be poor if herbicides are applied before there is sufficient regrowth. Existing vegetation that consists of small annual weeds less than 2 inches tall may not require the use of Gramoxone or Roundup as a knockdown herbicide. Residual herbicides that also have postemergence ac- tivity may often control existing vegetation. Bladex, atrazine, Sencor or Lexone, and Lorox or Linex have both preemergence and postemergence activity. Also, postemergence herbicides can often be used to control existing vegetation. Poast is labeled to control existing grass weeds before planting soybeans. Early preplant application of labeled residual her- bicides can often prevent vegetation from being a problem before planting. The earlier that applications are made before planting, the shorter the length of control after planting. To strengthen or lengthen con- trol, an additional application of the same or another herbicide at planting can be considered. Gramoxone (1 Vz to V^li pints per acre) plus a nonionic surfactant can be used to "knock down" existing foliage before crop emergence. Smartweed, giant rag- weed, and fall panicum may not be controlled if they are more than 4 to 6 inches high. A minimum of 40 gallons or more of spray per acre is suggested to ensure adequate coverage of the foliage. Gramoxone can be applied with certain liquid fertilizers. Do not apply with suspension or high-phosphate liquid fertilizers. Gra- moxone is a restricted-use pesticide. Roundup (3 to 8 pints per acre) is another alternative for control of existing vegetation before crop emergence in situations where fall panicum, smartweed, or certain perennial weeds are a problem. Roundup can trans- locate to the roots to give better control of perennials. Use 10 to 40 gallons of spray volume per acre. Roundup plus 2,4-D can be used in some situations to improve broadleaf control. For control of small annual weeds. Roundup can be used at a rate of 12 to 16 ounces per acre plus 0.5- percent nonionic surfactant in 5 to 10 gallons of spray solution per acre. Do not mix the Microtech formulation of Lasso with Roundup. Bronco is a formulated mixture of glyphosate (Roundup) plus alachlor (Lasso). Application rates are 4 to 5 quarts per acre. Bronco may be applied in 10 to 30 gallons of water or in 10 to 50 gallons of 28- percent or 32-percent liquid nitrogen solutions. Ap- plications with a nitrogen solution should be made only for control of annual weeds that are less than 6 inches tall. Roundup, Gramoxone, and Bronco are registered for use in combination with the preemergence herbi- cides indicated in Table 1. See the sections entitled "Herbicides for com" and "Herbicides for soybeans" for more information about these products. For control of broadleaf weeds in no-till programs for soybeans, 2,4-D may be used prior to 30 days before planting, with Surflan or Poast for grass control. Herbicides for corn Herbicides mentioned in this section are registered for use on field com and also on silage com unless otherwise specified. See Table 2 for registered combi- nations. Herbicide suggestions for sweet com and popcorn may be found in Circular 907, 2987 ]Need Management Guide for Commercial Vegetable Growers. Growers producing hybrid seed com should check with the contracting company or inbred-seed producer about tolerance of the parent lines. Banvel (dicamba) can be used as a preplant her- bicide before planting com or sorghum. The rate is 1 to 2 pints per acre. It is suggested that you delay planting com 1 week and sorghum 1 to 2 weeks after application. Roundup can be used preplant to com or sorghum at % to 1 pint (12 to 16 fluid ounces) per acre to control small annual weeds. Use 5 to 10 gallons of water per acre plus a nonionic surfactant. Roundup may be mixed with Banvel or 2,4-D. Preplant incorporated herbicides Some herbicides may be applied prior to planting and incorporated. The time of application will depend upon the label directions and field conditions. Herbi- cides with sufficient residual activity, such as AAtrex, Table 1. Registered No-Till Herbicide Combina- tions Alone Combination Dual Lasso Surflan Prowl Soybeans Amiben . . . .... GR GR GR GR GR Lorox .... GBR GR GBR GR G Lexone .... GBR GR GBR GR G Scepter . . . .... GBR GBR GBR — GBR Sencor .... GBR GR GBR GR G Turbo .... GR — — — — Corn Atrazine . . .... GBR GR GBR — — Bladex .... GBR G GBR — — Princep . . . Atrazine + .... BR GR GBR — — Bladex . . .... B G GB — — Atrazine + Princep . .... GBR GR GBR — — Bicep .... GR — — — — Knockdown herbicides: G = Gramoxone (paraquat) R = Roundup (glyphosate) B = Bronco = Roundup + Lasso — = Not registered Preplant not incorporated Interest in early preplant application is increasing, especially with the trend toward reduced tillage. Bladex and atrazine have postemergence as well as residual activity. Early weeds such as smartweed can be con- trolled while they are small, and emergence of other weeds can be curtailed. With AAtrex, Dual, or Bicep, preplant surface application may be made using a two-thirds rate as long as 45 days before planting, followed by a one- third rate at planting. A single application can be made within 30 days before planting. Bladex may be applied early preplant at labeled rates, but if applied earlier than 15 days before plant- ing, a split application or use of another herbicide at or after planting is suggested. Banvel or 2,4-D is labeled in mixture with Bladex, Bladex plus atrazine, and Bicep for com with minimum or no tillage. Table 2. Registered Herbicide Combinations for Preplant Incorporated (PPI), Preemerg- ence (Pre), or Early Postemergence (EPoE) Application in Corn ... Di J T> • Atrazine Atrazine Atrazine Bladex Pnncep ^ gj^^^^ ^ p^^^p PPI only Eradicane, Eradicane Extra 1 1 1 1 — Genate Plus 1 1 — 1 — Sutan + 1 1 1 1 — PPI or Pre or EPoE Used alone 1,2,3 1,2,3 1,2 1,2,3 1,2 Dual 1,2,3 1,2 1,2 1,2 1,2 Lasso 1,2,3 1,2 2 1,2 — 1 = Preplant incorporated 2 = Preemergence 3 = Early postemergence — = Not registered 6 Bleep, and Dual may be applied early preplant, as long as 45 days before planting. If these herbicides are applied too early, however, weed control may not last as long as desired after planting. Incorporation should distribute the herbicide uniformly throughout about the top 2 inches of soil. Do not apply herbicides too early or incorporate them too deeply. Sutan+, Genate Plus (butylate), Eradicane, and Eradicane Extra (EPTC) contain crop safening-agents. Crop injury is unlikely but may occur when growing conditions are unfavorable or when certain hybrids are used. Eradicane Extra also contains an extender to lengthen weed control. These herbicides control annual grass weeds and at higher rates can control or suppress shattercane and johnsongrass. The rate for Sutan+ and Genate Plus is 4% to 7y3 pints per acre. The rate for Eradicane 6.7E is 4% to ZVa pints per acre. The rate for Eradicane Extra 6E is SVa to 8 pints per acre. Use the higher rates for heavy infestations of shatter- cane and yellow nutsedge and for johnsongrass. Although these herbicides should be incorporated into the soil soon after application, some labels allow up to 4 hours for incorporation if applied to dry soil. Even though some labels allow application up to 4 weeks before planting, apphcation close to planting time is generally preferable. Research results indicate that satisfactory weed con- trol may be achieved by applying some of these products directly on soybean stubble in the spring and using one- or two-pass incorporation. Sutan-I-, Genate Plus, Eradicane, or Eradicane Extra can be tank-mixed with atrazine or Bladex to improve broadleaf control. Sutan+, Eradicane, or Eradicane Extra can be tank-mixed with Princep. The atrazine rate is 2 to 3 pints of 4L or equivalent amounts of SOW or 90WDG per acre. The Bladex rate is 3 to 4 pints of 4L or 2 to 2V2 pounds of SOW per acre. Three- way combinations with atrazine plus Bladex are also registered. These herbicides can be applied with Uquid fertilizer or impregnated on dry bulk fertilizer. Sutazine-I- 6-ME is a 4:1 mixture of Sutan-h and atrazine. The application rate is bVi to lOVa pints per acre. Sutazine-I- 1S:6G and Sutan-I- lOG are as granular formulations. Sutazine has 4.8 plus 1.2 pounds per gallon. Rhino also is a butylate-plus-atrazine combi- nation with 4.3 pounds plus 1.7 pounds per gallon. Preplant or preemergence herbicides Incorporation of the following herbicides is optional, depending upon the weeds to be controlled and the likelihood of rainfall. Incorporation of these herbicides should be shallow but thorough. AAtrex, Atrazine (atrazine), or Princep (simazine) can be applied anytime during the 2 weeks before planting or soon after planting. If rainfall is limited, incorporation may aid performance. Com tolerance of atrazine and simazine is good, but carryover to sub- sequent crops can occur. Princep controls fall panicum and crabgrass better than atrazine does but is less effective in controlling cocklebur, velvetleaf, and yellow nutsedge. Princep is less soluble and more persistent than atrazine; thus Princep is usually apphed preplant. Princep plus atra- zine can be used in 1:1 or 2:1 combinations; the total rate is the same as for atrazine used alone. The rate for atrazine used alone is IVi to 3% pounds of atrazine SOW, 4 to 6 pints of 4L, or 2.2 to 3.3 pounds of AAtrex Nine-0. Atrazine controls annual broadleaf weeds better than it does grasses, and it is often used at reduced rates in tank-mix combinations to improve broadleaf weed control. The rate for atra- zine in combinations is IV2 to 2 pounds of atrazine SOW, 2 to 3 pints of atrazine 4L, or 1.1 to 1.8 pounds of AAtrex Nine-O. These rates may not provide ade- quate control of cocklebur, momingglory, and velvet- leaf but can reduce the risk of carryover. You can minimize carryover injury by mixing and applying the herbicides accurately, by applying them early, by using the lowest rates consistent with good weed control, and by tilling the soil to dilute the herbicide. The risk of carryover is greater after a cool, dry season and on soils with a pH over 7.3. If you use atrazine at more than 3 pounds of active ingredient per acre (lbs a.i./A) or if you apply after June 10, plant only corn or sorghum the next year. If you use atrazine in the spring and must replant, then plant only com or sorghum that year. Do not plant small grains, small-seeded legumes, or vegetables in the fall or the following spring. Soybeans planted the year after an application of atrazine can also be affected by carryover, especially if you use Sencor or Lexone. Bladex (cyanazine) does not persist in the soil as long as atrazine, but atrazine does have the advantage of better com tolerance. Bladex provides better control than atrazine of fall panicum, giant foxtail, and some other grass weeds but may not be quite as good as atrazine on some broadleaf weeds, especially pigweed. Bladex can be combined with atrazine in a 3:1, 2:1, or 1:1 ratio of Bladex to atrazine (see label for rates). The higher ratios will provide better grass control, while the 1:1 ratio will provide better broadleaf weed control. Prepackaged combinattons include Extrazine (2:1 ratio) and Conquest (3:1 ratio). Rates of Bladex must be selected accurately on the basis of soil texture and organic matter to reduce the possibility of com injury. The rate for Bladex is IV2 to 6 pounds of SOW, 1.35 to 5.3 pounds of Bladex 90DF, or Vk to 4% quarts of 4L. You can lessen the risk of injury to com by using reduced rates of Bladex in combinations. Bladex can be tank-mixed with Lasso, Dual, Ramrod, or Prowl to improve grass control. The Lasso or Dual combination can be applied immediately before plant- ing or after planting. Do not incorporate the Prowl or Ramrod combinations. Three-way combinations of Bladex plus atrazine plus Lasso, Dual, Sutan-I-, Eradicane, or Eradicane Extra are registered. The addition of a limited amount of atrazine should improve broadleaf control without increasing concern about carr^'over. Bladex is classified for restricted use by certified applicators. Lasso (alachlor) or Dual (metolachlor) can be pre- plant incorporated or applied preemergence at planting time. Preplant incorporation of these herbicides can improve control of yellow nutsedge and can lessen dependence upon rainfall. Incorporation should dis- tribute the herbicide evenly throughout the top 2 inches of soil. Lasso and Dual control annual grasses and help control yellow nutsedge. You can improve broadleaf weed control by using atrazine, Bladex, or both in either a preplant or a preemergence combination. Lasso can be applied any time during the week before planting corn and shallowly incorporated, or it can be used after planting but before the crop and weeds emerge and within 5 days after the last tillage operation. The rate is 2 to 4 quarts of Lasso 4E or 16 to 26 pounds of Lasso 15G. Use the higher rate suggested for the type of soil if you plan to incorporate Lasso. Dual can be applied any time during the 2 weeks before planting com and shallowly incorporated, or it can be used soon after planting. The rates are IV2 to 4 pints of Dual 8E or 6 to 16 pounds of Dual 25G per acre. Lasso or Dual plus atrazine can be preplant in- corporated or applied after planting until com is 5 inches tall and grass weeds have not passed the 2- leaf stage. Do not apply with liquid fertilizer after the crop emerges. The suggested rate is IV2 to 4 quarts of Lasso or VA to 2V2 pints of Dual 8E plus IV2 to 2V2 pounds of atrazine SOW, 1 to 2 quarts of atrazine 4L, or 1.1 to 2.2 pounds of AAtrex Nine-O. Dual is also cleared in a combination with atrazine plus Princep. Dual and Lasso are both formulated as packaged mixes with atiazine. Bicep contains a 5:4 ratio of metolachlor (Dual): atrazine per gallon. The rate is Vh to 3 quarts of Bicep 6L per acre. Lasso/atrazine (flowable) contains 2V2 pounds of alachlor (Lasso) and IV2 pounds of atrazine per gallon. The rate is 3V2 to 4V2 quarts per acre. Dual or Lasso plus Bladex can be applied before planting and incorporated, or they can be appUed preemergence at planting. The rate is 2 to 4 quarts of Lasso 4E or PA to 2V2 pints of Dual 8E plus 1 to 3% pounds of Bladex SOW or 1 to 3 quarts of Bladex 4L. Adjust the rate carefully according to soil texture and organic matter. Preemergence herbicides Ramrod (propachlor) can be applied alone before crop or weeds emerge or with atiazine after the com is planted but before grasses reach the 2-leaf stage and com emerges. Granular formulations should be applied before crop or weeds emerge. Ramrod performs well on soils with more than 3-percent organic matter. Ramrod is irritating to the skin and eyes, so observe label precautions. Com tolerance is good. Ramrod contiols annual grasses and pigweed. The rate is 4 to 6 quarts of Ramrod 4L or 20 to 30 pounds of 20G per acre. Banvel (dlcamba) can be applied alone after plant- ing as long as com is no more than 5 inches tall. Banvel is approved for use in combinations with Lasso, Dual, atiazine, or Bladex. Banvel may injure com, especially if recommended rates are exceeded, if ap- plications are not accurate and uniform, or if com is planted too shallow (less than 1 V2 inches). Do not use this tieatment on coarse-textured soils or soils that are low in organic matter. The rate on fine-textured soils with more than lV2-percent organic matter is one pint of Banvel. Prowl (pendimethalin) is registered only for use on com after planting. Incorporation of Prowl may result in serious injury to com. Use only where it is possible to cover seed adequately with soil. Prowl can contiol annual grasses, pigweed, and lambsquarters; and it may provide some contiol of smartweed and velvetleaf. You can improve broadleaf weed contiol by combining Prowl with atiazine, Bladex, or Banvel. Prowl plus atiazine or Bladex may be applied in the early postemergence period before grasses are in the 2-leaf stage. These combinations may also help reduce the competition from wild proso millet. But avoid postemergence application when com is under stiess from cool, wet weather; otherwise, injury to com may result. The rate for such combinations is 1 to IV2 quarts of Prowl 4E. Do not use Prowl plus Banvel on sandy soils or soils with less than IV2 -percent organic matter. Postemergence herbicides Lasso, Dual, Ramrod, or Prowl may be combined with atiazine for application after planting to very early postemergence. The same is true for Lasso or Dual combined with Banvel. To obtain satisfactory control, apply before grasses reach the 2-leaf stage. For more information about postemergence principles, see the section entitled "Postemergence herbicide prin- ciples." Atrazine can be apphed when grass weeds are no more than V/i inches high. Many annual broadleaf seedlings are more susceptible than grass weeds and may be tieated until they are 4 inches tall. For contiol of some broadleaf weeds, 1.2 pounds active ingredient of atiazine may be insufficient. In most cases, this rate will need to be increased to 2 pounds for contiol of annual grass weeds. The addition of oil-surfactant mixes or surfactants has generally increased the effectiveness of post- emergence atiazine. Crop-oil concentiates (80-percent oil and 20-percent surfactant) are used at the rate of one quart per acre. Surfactants are usually added at 0.5 percent of the total spray volume or at a rate of about one pint per acre. Results with the oil-surfactant mixes have generally been better than those with surfactants. An atrazine-and-oil mix sometimes damages com that has been under stress from prolonged cold, wet weather or other factors. Do not use more than Vli pounds of atrazine SOW, 2 quarts of atrazine 4L, or 2.2 pounds AAtrex Nine-O per acre if you mix with oil or oil concentrate. Do not add 2,4-D to the atrazine- oil treatment, or severe injury may result. Mix the atrazine with water first, and add the oil last. If atrazine is applied after June 10, do not plant any crop except com or sorghum the next year. Bladex (cyanazine) can be applied until the fifth leaf of corn is visible and before grass weeds exceed IV2 inches in height. The Bladex rate is IV2 to IVi pounds of SOW or 1.1 to 2.2 pounds of 90DF per acre. Do not use Bladex 4L because it contains oil and can increase the potential for injury. Injury to com may occur under cold, adverse growing conditions. The injury may be only temporary yellowing but can be more severe. Under droughty conditions, certain ag- ricultural surfactants or vegetable oils may be added to Bladex SOW to improve weed control. Do not use petroleum crop oils or apply with liquid fertilizers for postemergence application. Do not apply Bladex post- emergence on com that is under severe stress. One may combine Bladex SOW with atrazine SOW, substituting atrazine for 30 percent of the Bladex. Also registered is a Bladex plus Banvel combination that allows for the addition of one-half to two-thirds pint of Banvel per acre; no surfactant or any type of oil should be added to this combination. Bladex is classified as a restricted-use pesticide. Tandem (tridiphane) may be used with atrazine, Bladex, or both for postemergence control of both annual grass and broadleaf weeds in field com. These combinations should be applied when annual grass weeds are in the 1- to 3-leaf stage and actively growing. Tandem rates are 1 to IV2 pints per acre. Atrazine SOW 90DF, or 4L may be used; but only Bladex SOW should be used with Tandem. Atrazine 4L rates are IV2 to 4 pints, and Bladex SOW rates are 1 to 2V2 pounds per acre. Rates are adjusted for soil, type of weeds, and tank-mixture being used. Crop oil or crop- oil concentrate should be added to the Tandem-atrazine combination. Do not apply combinations containing Bladex to com with more than four true leaves or to corn under stress from cold or wet weather. Do not spray if rain is expected within 3 hours. Precautions for avoiding injury to subsequent crops are similar to those for atrazine. Banvel (dicamba) can be applied from emergence until corn is 36 inches tall or until 15 days before tassel emergence, whichever comes first. Best results can be expected by using one-half to one pint of Banvel per acre when the com is in the spike to 5- inch stage. Application at this time can offer several weeks of soil (residual) activity when the 1-pint rate is used. With this timing, crop tolerance is better than with preemergence treatments of Banvel. In addition, application rates can be higher than with the later postemergence treatment, and the likelihood of injury to nearby soybeans is diminished. For applications on corn from 5 to 36 inches tall, the rate is one-half pint per acre. Banvel is labeled as an overlay (sequential) treatment following Sutan-I-, Eradicane, Lasso, Dual, Bicep, Ramrod, atrazine, Bladex, Princep, Roundup, Bronco, or paraquat. Banvel is also labeled for postemergence use as a tank-mix with atrazine, Bladex SOW, or 2,4-D. The postemergence rate for Banvel is one-half pint (one- fourth pound active ingredient) per acre after com is 5 inches tall. The label allows for the addition of one- eighth to one-fourth pound of 2,4-D add equivalent per treated acre. If Banvel or Banvel plus 2,4-D is used on com that is taller than S inches, drop pipes should be used to help keep the spray off the com leaves and out of the whorl. For best results, use Banvel before June 20 with a spray volume of 20 gallons per acre and a spray pressure of no more than 20 psi to help reduce the risk to plants outside the target area. Do not apply Banvel when soybeans are growing nearby if com is more than 24 inches tall, soybeans are more than 10 inches tall, or soybeans have begun to bloom. To aid in the control of hemp dogbane, Banvel is approved for use at one-half pint with one pound acid equivalent per acre of 2,4-D D/ ester or amine after com is in the brown silk stage but at least 7 days before harvest. Marksman (dicamba plus atrazine) is a formulated mixture of 1.1 pound dicamba (active ingredient of Banvel) and 2.1 pounds of atrazine per gallon. The rate is 2 to 3.5 pints per acre, depending on the soil texture and organic-matter content. On most Illinois soils, the rate is 3.5 pints per acre or 0.48 pound of dicamba and 0.92 pound of atrazine per acre. Marks- man is cleared as a tank-mix and in sequential com- binations with many other herbicides. Marksman may be applied to actively growing weeds before, during, or after planting but before com exceeds the 5-leaf stage. In most conventional tillage applications, the recommended timing is from emer- gence to the 5-leaf stage of com. Most annual broadleaf weeds should be controlled, and some perennial broad- leaf weeds should be suppressed. This formulated mixture will be targeted at the velvetleaf market in Illinois, where Banvel has needed some help. 2,4-D is effective in controlling many broadleaf weeds in com. If com is more than S inches high, use drop nozzles to decrease the possibility of injury. If you direct the nozzles toward the row, adjust the spray concentration so that excessive amounts are not applied to the com. Do not apply 2,4-D to com from the tasseling stage to the dough stage. After the hard dough to dent stage, you can apply 1 to 2 pints of certain 2,4-Ds by air or high-clearance equipment to control some broad- leaf weeds that may interfere with harvest or to suppress certain perennial weeds. Do not forage or feed fodder for 7 days after treatment. The suggested broadcast rate is one-third to one- half pint of ester or one pint of amine for formulations with 3.8 pounds of 2,4-D acid equivalent per gallon. Use equivalent rates with other formulation concen- trations. Use proportionately less 2,4-D when using directed nozzles. The ester forms of 2,4-D can vaporize and injure nearby susceptible plants. This vapor movement is more likely with high-volatile esters than with low- volatile esters. Spray particles of either the ester or the amine form can drift and cause injury. Corn is often brittle for 7 to 10 days after application of 2,4-D and thus is susceptible to stalk breakage from high winds or cultivation. Other symptoms of 2,4-D injury are stalk bending or lodging, abnormal brace roots, and failure of leaves to unroll. Injury problems are unlikely once com has reached the brown silk stage. High temperature and high humidity can increase the potential for 2,4-D injury, especially if com is growing rapidly. If it is necessary to spray under these conditions, it may be wise to reduce the rate by about 25 percent. Com hybrids differ in their sensitivity, and the probability of injury increases when com is under stress. Buctril or Brominal (bromoxynil) may be used to control broadleaf weeds in field and silage com. It is important to treat when the weeds are small. For ground applications, use 20 gallons of water per acre, a spray pressure of 30 psi, and flat-fan nozzles. Bromoxynil will not volatilize and cause the drift injury associated with 2,4-D or Banvel. Bromoxynil, under some conditions, may cause some burning of com leaves, but the effects are usually temporary. Do not add a surfactant or crop oil to Buctril or Brominal used alone or in combination. Buctril 2E rates are 1 to IV2 pints per acre when com and weeds are in the 3- to 8 -leaf stage. Brominal 4E rates are one-half to one pint per acre when com is in the 2 -leaf to 14 -inch stage and before weeds are 4 to 6 inches tall. Use the higher rate on larger com and weeds. Most annual broadleaf weeds are con- trolled. Larger pigweed and velvetleaf may require the higher rate or a combination with atrazine. Atrazine 4L at 0.5 to 1.0 quart (or equivalent rates of 80W or 90DF) can be combined with Buctril or Brominal. Do not add Bladex to bromoxynil. Buctril plus atrazine is a formulated combination of 1 pound bromoxynil plus 2 pounds atrazine active ingredient per gallon for application at IV2 to 2 pints per acre at the 3- to 8-leaf stage of com or at 3 pints at the 4- to 8-leaf stage. The lower rates are for smaller weeds. Brominal and atrazine have been packaged in sep- arate containers in a Torch twin-pack. Basagran (bentazon) is registered for postemergence use in corn, with recommendations similar to those given for use with soybeans. (See the section entitled "Herbicides for soybeans.") The rate is V/2 to 2 pints of Basagran 4S per acre. Crop-oil concentrate may be added at one quart per acre. Basagran is also cleared at the rate of 1 to IV2 pints per acre in combination with atrazine at 0.6 to 1.0 pound of SOW, 0.6 to 0.9 pound of 90DF, or 1 to IV2 pints of 4L per acre. Laddok is a 1:1 ratio mix of bentazon and atrazine for use in com. Crop-oil concentrate is added at one quart per acre. This combination controls only annual broad- leaf weeds and not annual grasses. The combination provides better control of pigweed and lambsquarters than does Basagran alone and will create less risk of carryover than does atrazine alone. Roundup (glyphosate) may be applied as a spot treatment in com prior to silking. For applications made on a spray-to-wet basis, use a 1- to 2-percent solution of Roundup in water. For motorized spot treatments in which less than complete coverage of weeds may result, use a 5 -percent solution. Avoid contact of spray with the com. Add a dye for increased visibility. Postemergence soil-applied herbicides Prowl, Treflan, or Lasso can be applied to the soil as a postemergence treatment in com. It may be necessary to use drop nozzles to avoid interference from com leaves and to ensure uniform application to the soil. Prowl (pendimethalin) or Treflan (trifluralin) may be applied to the soil and incorporated after field com is 4 inches tall (for Prowl) or 8 inches tall (for Treflan) and up to the time of the last cultivation. The field should be cultivated to control existing weeds and cover the roots at the base of the com before appli- cation. The herbicide should then be thoroughly and uniformly incorporated into the top inch of the soil with a sweep-type or rolling cultivator. Prowl may not need to be incorporated if irrigation is used or rainfall occurs soon after application. Prowl or Treflan can be combined with atrazine. These Prowl or Treflan treatments may help control late-emerging grasses such as shattercane, wild proso millet, fall panicum, or woolly cupgrass. Lasso (alachlor) may be used alone or with atrazine as a soil-applied postemergence treatment to help control midseason annual grass weeds in com that is grown for seed. Application should preferably be made after cultivation — before weeds emerge and before the crop is 40 inches tall. Dual (metolachlor) or Bleep (metolachlor plus atrazine) may be used for postemergence "layby" treatments in com. For Dual, as much as 3 pounds active ingredient per acre may be used in a single application, up to a total of 6 pounds active ingredient in one year. With Bicep, as much as 3 quarts of 6L may be used per acre. 10 Directed postemergence herbicides Directed sprays are sometimes needed for emer- gency situations, especially when grass weeds become too tall to be controlled by cultivation. Weeds, however, are often too large for directed sprays to be effective. Directed sprays cannot be used on small com because a height difference between com and weeds is needed to keep the spray off the com. Com leaves that come into contact with the spray can be killed, and injury may affect yields. Lorox or Linex (linuron) may be applied as a directed spray after corn is at least 15 inches tall (freestanding) but before weeds are 8 inches tall, preferably when weeds are no more than 5 inches tall. Linuron controls broadleaf and grass weeds. The broadcast rate is 1 "^k to 3 pounds of Lorox SOW (or 50DF) or 1 V4 to 3 pints of 4L per acre, depending on weed size and soil type. Add Surfactant WK at the rate of 1 pint per 25 gallons of spray mixture. Cover the weeds with the spray, but keep it off the corn as much as possible. Consider this an emergency treatment. Evik SOW (ametryn) is registered for directed use when corn is more than 12 inches tall and weeds are less than 6 inches tall. Evik should not be applied within 3 weeks of tasseling. The rate is 2 to 2V2 pounds Evik SOW per acre (broadcast) plus 2 quarts of sur- factant per 100 gallons of spray mixture. Extreme care is necessary to keep the spray from contacting the leaves. Consider this an emergency treatment. Herbicides for sorghum Many herbicides used to control weeds in com can also be used in sorghum. Atrazine may be used for weed control in sorghum (grain and forage types) or sorghum-sudan hybrids. Application may be made preemergence or post- emergence. A preplant surface appHcation may be made using a single application within 30 days of planting or a two-thirds plus one-third split application within 45 days of planting. Plant seed at least one inch deep. Do not use preplant or preemergence on soils with less than 1 -percent organic matter. Incor- porated treatments may cause injury if rainfall occurs before or shortly after sorghum emergence. Injury may occur when sorghum is under stress from unusual soil or weather conditions or when rates are too high. The rate of application for preplant and preemergence is 2 to 3 pounds of atrazine SOW per acre. The postemergence rate is 4 to 6 pints 4L per acre without crop oil or 2.4 pints 4L (broadleaf control only) with crop oil or crop-oil concentrate. Use equiv- alent rates of atrazine SOW or AAtrex 90DF formu- lations. Rotational crop recommendations and weed control are the same as for atrazine used in com. Failure to control fall panicum has been a major problem. Ramrod (propachlor) may be used alone or in combination with atrazine, Milogard, Bladex, or Mo- down for sorghum. Ramrod can improve grass control; but rates must not be skimpy, especially on soils that are relatively low in organic matter. For specific rates, consult the label. Do not graze or feed forage to dairy animals. Lasso (alachlor) alone or plus atrazine may be preplant incorporated or used preemergence for grain sorghum if seed is treated with Screen (flurazole). This use also applies to Lasso/atrazine and to Bronco. Dual (metolachlor) or Bleep (metolachlor plus atrazine) can be used for sorghum if seed has been treated with Concep. These herbicides will control grasses better than will atrazine applied alone. An early preplant treatment of Dual or Bicep may be used in a similar manner as for com, but it is still necessary to use seed that has been treated with Concep. Modown 4F (bifenox) may be used preemergence at 3 to 4 pints per acre for all soil types. Broadleaf weeds controlled include nightshade, jimsonweed, lambsquarters, smartweed, pigweed, and velvetleaf. Basagran (bentazon) is registered for postemergence use in sorghum in a manner similar to that for com. (See the section entitled "Herbicides for com.") Because sorghum is quite tolerant of Basagran up to and including early boot stage, the addition of a crop-oil concentrate is considered relatively safe. Do not apply to grain sorghum that is heading or blooming. Apply Basagran at the rate of 1 to IV2 pints in combination with atrazine at 0.6 to 1.0 pound of SOW, 0.6 to 0.9 pound of 90WDG, or 1 to IVi pints of 4L per acre. 2,4-D may be applied postemergence for broadleaf control in sorghum that is from 4 to 24 inches tall. Use drop pipes on nozzles if sorghum is more than 8 inches tall. Rates are similar to those for use in com. (See the section entitled "Herbicides for com.") Banvel (dicamba) may be applied postemergence to sorghum up to 21 days after emergence but before sorghum is 15 inches tall. The rate is one-half pint per acre. Do not graze or feed treated forage or silage before the mature grain stage. Sorghum can be injured by Banvel, and seed development can be affected. Brominal or Buctril (bromoxynil) can control broadleaf weeds in grain sorghum that is past the 3- leaf stage and as much as 14 inches tall and before weeds are 4 to 6 inches tall. It is generally safer than 2,4-D on grain sorghum. Combinations with atrazine are also registered to improve pigweed control and provide some residual control of germinating seedlings. Buctril plus atrazine may be used postemergence for grain sorghum at IV2, 2, or 3 pints per acre from the 2-, 3-, or 4-leaf stage, respectively, up to the 10- leaf stage — but not on sorghum that is more than 10 inches tall. The Torch twin-pack, with separate con- tainers of Brominal and atrazine, is also approved for sorghum as well as corn. Prowl (pendimethalin) may be applied to grain sorghum from the 4 -inch growth stage to as late as 11 the last cultivation, primarily for control of late-season annual grass weeds. For more information, see the section entitled "Herbicides for com," subsection on postemergence soil-applied herbicides. Roundup (glyphosate) may be applied as a spot treatment in sorghum (milo) prior to heading. For applications on a spray-to-wet basis, use a 1- to 2- percent solution of Roundup in water. With motorized spot treatments from which less complete coverage of weeds may result, use a 5 -percent solution. Avoid contact with the sorghum. Add a dye for increased visibility. Bronco (glyphosate plus alachlor) may be used alone or with atrazine where grain sorghum is to be planted directly into a cover crop or in the residue of the previous crop. Bronco can control emerged annual weeds and suppress many emerged perennial weeds, as well as give preemergence control. Grain sorghum seed must be treated with Screen, as it is when Lasso is used. Gramoxone may be used for control of annual weeds where grain sorghum is to be planted into the residue of the previous crop. Herbicides for soybeans Consider the kinds of weeds expected when you plan a herbicide program for soybeans, especially when growing soybeans in narrow rows. The herbicide se- lectivity table lists herbicides and their relative weed control ratings for various weeds. (See Table 5 at the end of this guide.) Although soybeans may be injured by some her- bicides, they usually outgrow early injury with little or no effect on yield if stands have not been signifi- cantly reduced. Significant yield decreases can result when injury occurs during the bloom to pod-fill stages. Excessively shallow planting may increase the risk of injury from some herbicides. Accurate rate selection for soil type is especially essential for Lorox, Linex, Lexone, Sencor, or Turbo. Do not apply Lorox, Linex, Lexone, Sencor, Turbo, or Modown after soybeans begin to emerge. Follow label instructions for rates, timing, incorporation, and restrictions. For registered combinations, see Table 3. Preplant not incorporated Early preplant application can be used in many conservation tillage programs — such as no-till, ridge- till, or mulch-till — to minimize existing vegetation problems at planting and thus reduce the need for knockdown herbicides. Lorox or Linex (linuron) and Sencor or Lexone (metribuzin) have both postemer- gence and residual activity, but postemergence activity varies with climatic conditions. If weeds have emerged before preplant application, the use of a foliar knock- down herbicide such as Gramoxone or Roundup may be necessary. (See the section entitled "Conservation tillage and weed control," subsection on no-till and double-crop.) Several preemergence herbicides are registered for application before planting soybeans. Surflan (oryzalin) can be applied any time before planting no-till soybeans. Surflan can be applied in fully tillered wheat before heading, and soybeans can then be planted no-till into wheat before harvest or in wheat stubble immediately after harvest. Surflan is also labeled for tank-mixing with 2,4-D prior to 30 days before planting to control established winter weeds where soybeans are to be planted no- till. To control existing vegetation, Gramoxone or Roundup combinations with Surflan plus Sencor or Lexone can be applied before planting no-till soybeans. Surflan plus Lexone can be applied as much as 30 days before planting. Dual (metolarchlor) can be applied within 30 days before planting soybeans or as a split application using a two-thirds rate as long as 45 days before planting, followed by a one-third rate at planting. Either Turbo alone or Sencor applied with Dual or Lasso can be applied 15 to 30 days before planting soybeans when using a sequential (split) preemergence application: the first made early, followed by the second at planting. Some foliar postemergence herbicides can also be used before planting soybeans. Roundup (glyphosate) can also be used preplant in soybeans to control small annual weeds. The rate is 12 to 16 fluid ounces (% to 1 pint) per acre in 5 to 10 gallons of water, with the addition of a surfactant. Poast (sethoxydim) may be apphed before planting soybeans, with no time interval restriction. Poast plus 2,4-D (LVE) as a tank-mix may be applied prior to 30 days before soybean planting. Recom- mended use rates per acre are V2 pint Poast and 1 pint 2,4-D (V2 pound acid equivalent) with 2 pints crop-oil concentrate in 5 to 10 gallons of spray solution. Preplant incorporated herbicides Incorporation is required for Treflan, Sonalan, Ver- nam, and Reward. Incorporation of Command will be required to reduce movement outside the target area. Incorporation is optional for Amiben, Preview, Dual, Lasso, Modown, Prowl, and Scepter when used alone or in some combinations. Lorox Plus, Lorox, and Surflan should not be incorporated. Incorporation can improve performance if rainfall is linuted and may increase the effectiveness of Dual or Lasso in controlling nutsedge. Incorporation should distribute the herbicide evenly in the top 1 to 3 inches of soil. Deep incorporation or very early application of the herbicide can cause significant reductions in weed control. For more information, see the section entitled "Herbicide incorporation." Dinitroaniline herbicides registered for weed con- 12 Table 3. Registered Herbicide Combinations for Preplant Incorporated (PPI) or Preemergence (Pre) Use in Soybeans Amiben Sencor or Lexone Command Preview'' Lorox Scepter Command + Sencor or Lexone PPI Sonalan 1 Treflan 1 Command — PPI or Pre Dual 1,2 Lasso 1,2 Prowl 1,2 Surflan^ 2 1 = Preplant incorporated 2 = Preemergence — = Not registered ^ Not for preplant incorporation ^ Pending 1 1 1 1 1 — 1 1 1 1 1 1,2 1,2 1,2 2 1 1 1 2 2 2 2 1,2 1,2 1,2 1,2 — — trol in soybeans are Treflan, Prowl, Sonalan, and Surflan. Treflan and Sonalan should be incorporated because they have low solubility and are subject to loss by vaporization and photodecomposition. Incor- poration is optional with Prowl, but variable weed control and soybean injury may result if Prowl is not incorporated. Incorporation should distribute the her- bicide uniformly throughout the top 2 to 3 inches of soil (see label for implement settings). Do not incor- porate Surflan. (See the subsection about preemergence herbicides.) The dinitroaniline herbicides control annual grasses, pigweed, and lambsquarters and may provide some control of smartweed and annual momingglory. Prowl and Surflan may also partially control velvetleaf. Ac- ceptable control of most other broadleaf weeds requires combinations or sequential treatments with other her- bicides. Soybeans are sometimes injured by dinitroaniline herbicides. Plants that have been injured by incor- porated treatments may be stunted and have swollen hypocotyls and shortened lateral roots. Usually, such injuries are not serious. At the level of the soil surface, plants injured by preemergence apphcations may have stem calluses, which can cause lodging and yield loss. Com, sorghum, and small grains may be injured if they are grown after a soybean crop that has been treated with a dinitroaniline herbicide. The symptoms are poor germination and stunted, purple plants with poor root systems. To avoid carryover, use no more than the recommended rates and be sure that appli- cation and incorporation are uniform. The likelihood of carryover increases with double-cropping or late application and after a cool, dry season. Adequate tillage may help dilute herbicide residue, which helps alleviate a carryover problem. Treflan (trifluralin) may be applied alone any time in the spring. Combinations with Sencor or Lexone should be applied no more than 2 weeks before planting. Incorporate as soon as possible, but do not delay incorporation more than 24 hours (or more than 8 hours if soil is warm and moist). The rate is 1 to 2 pints of Treflan 4E or MTF, 0.8 to 1.6 pints of Treflan Pro-5, or 5 to 10 pounds of Treflan lOG per acre. Treflan MTF is a multi temperature formulation that helps to avoid problems associated with freezing in storage. Treflan Pro-5 contains 5 pounds trifluralin per gallon. Treflan may be tank-mixed with Scepter as a pre- plant incorporated (PPI) treatment or applied alone PPI followed by Scepter after planting but before soybean emergence. Treflan may be tank-mixed with Command or Com- mand plus Lexone or Sencor. Sonalan (ethalfluralin) may be applied vdthin 3 weeks before planting and should be incorporated within 2 days after appHcation. The rate for general weed control ranges from IV2 to 3 pints per acre, depending on soil texture. Sonalan may provide some control of nightshade at rates of 3 to 3V2 pints per acre, but for this purpose it should be used in con- junction with Amiben, Dual, or Lasso or followed vnth Blazer or Tackle. Sonalan provides more risk of injury to soybeans than does Treflan; however, Sonalan is less likely to injure com following soybeans than is Treflan. Sonalan may be tank-mixed with Amiben, Lasso, Dual, metribuzin. Reward, Command, or Scep- ter. Scepter may be tank-mixed with Sonalan or used preemergence or early postemergence following Son- alan. Sonalan may be tank-mixed with Command or Command plus Lexone or Sencor. Sencor or Lexone (metribuzin) plus Treflan, Son- alan, or Prowl can be tank-mixed and applied within 7 to 14 days of planting. Incorporate uniformly into the top 2 inches of soil. The rate of Sencor or Lexone in these combinations is one-half to one pint of 4L or one-third to two-thirds pound of 75DF. Use the normal rate, or slightly less, of the dinitroaniline herbicide (see labels). The application of Sencor or Lexone can also be 13 split, one part being incorporated and the other part applied to the surface preemergence. This method requires two applications but can give better broadleaf control and less injury than incorporating the same total amount of Sencor or Lexone in a single appli- cation. Command (FMC-57020) was initially marketed as a 6EC but will be a 4EC in 1987. It will be registered for use in combination with Sencor/Lexone by FMC and for use with Treflan or Sonalan by Elanco. Rates will be three-fourths to one pound of active ingredient (IV: to 2 pints) per acre for Command alone or in the combinations on the Command label and three-eighths to three-fourths pound of active ingredient on Treflan and Sonalan labels. The Elanco labels also include three-way combinations with metribuzin. Command should be incorporated to reduce movement outside the target area. Incorporation should preferably be done immediately, and it should provide uniform distribution. If a delay for incorporation is necessary, it should not exceed 3 hours. Command may be followed by some surface-applied preemergence her- bicides or a postemergence treatment. Soybeans have good tolerance to Command, and at adequate rates it can give good control of annual grass weeds. Command is exceptionally good on vel- vetleaf and can give good control of lambsquarters, smartweed, jimsonweed, common ragweed, and venice mallow. It needs help on pigweed, cocklebur, and black nightshade. Control of ivyleaf and tall momingglories should not be expected. Command should not be followed by small grain or alfalfa in the fall or next spring, and some other small-seeded legumes may be questionable. Other rotational crops, including com and sorghum, should not be planted for 9 months following application of Conrmiand. In the next season, do not follow with com for seed production. Cover crops may follow, but stand reductions may sometimes occur. Applications should be accurate and uniform to avoid overlaps and excessive rates, especially on field ends and odd- shaped fields. Under some weather and soil conditions, and with certain com hybrids, some effects may be noted the following season, especially if excessive amounts are applied or applications are not uniform. Some desirable plants — including ornamentals, trees, vegetables, and agronomic crops such as small grains and alfalfa — are sensitive to Command. Spray drift or vapors moving outside the target area may cause visible symptoms of chlorosis or bleaching of sensitive plants growing near treated fields. Do not spray where there is risk of the herbicide's moving to desirable plants that are sensitive to Command. Avoid windy conditions and conditions in which moisture evaporating from moist soil may carry the herbicide. Use care in rinsing equipment to avoid movement to desirable plants and to avoid tank contamination that can affect crops sprayed later. Amiben (chloramben) can be incorporated with Treflan, Sonalan, or Prowl. The rate is 4 to 6 quarts of Amiben 2S or 2.4 to 3.6 pounds of 75DS per acre. Amiben can also be applied and incorporated with Treflan or Prowl plus Sencor or Lexone as a three- way combination. Reward (vernolate plus extender) and Vernam (vernolate) control annual grasses and pigweed. They sometimes provide fair control of annual momingglory, velvetleaf, and yellow nutsedge. Some soybean injury may occur in the form of delayed emergence, stunting, and leaf crinkling. Vernam 7E or Reward 6E can be applied within 10 days before planting and should be incorporated immediately. The broadcast rate is 2y3 to 3V2 pints of Vernam 7E, 20 to 30 pounds of Vernam lOG, or 2% to 4 pints Reward 6E per acre. Vemam or Reward plus Treflan is labeled at the rate of 1 pint of Treflan plus 2V3 to 3 pints of Vemam 7E or 2% to 4 pints Reward 6E per acre. The combination may reduce the risk of injury to soybeans. For yellow nutsedge and velvetleaf control, use at least 3 pints of Vemam 7E or 3V3 pints of Reward 6E per acre. Other labeled combinations include Vemam or Reward plus Amiben, Sonalan, Prowl, Lasso, Furloe, Treflan/Sencor or Lex- one. Reward and Vemam can be applied with liquid fertilizer or impregnated on dry bulk fertilizer. Preplant or preemergence herbicides Prowl (pendimethalin) can be applied within 60 days before planting soybeans or applied after planting when used alone; Prowl with Sencor or Lexone can be applied within 7 days before planting soybeans or applied after planting. (See the subsection about pre- emergence herbicides.) Preplant treatments should be incorporated within 7 days of application. Mechanical incorporation may not be necessary if adequate rainfall occurs. Rates are 1 to 3 pints of Prowl 4E per acre, although rates for combinations with Sencor or Lexone are lower than when the herbicide is used alone. Prowl (pendimethalin) may be applied preemer- gence in combination with Amiben, Lorox, Lexone, or Sencor. When applied to the soil surface. Prowl may cause stem callusing, which can lead to soybean lodg- ing. (For more information, see the subsection about preplant herbicides.) Lasso (alachlor) or Dual (metolachlor) may be applied to soybeans as a preplant incorporated or preemergence treatment. Lasso may be applied within one week of planting. In a single treatment. Dual may be apphed to the soil surface early preplant within 30 days before planting. Or a two-thirds rate can be used within. 45 days of planting, along with a one-third rate at planting. Soybeans are quite tolerant of Lasso or Dual. The first- to second-tiifoliolate leaves often appear crinkled and have a drawstring effect on the middle leaflet, but these symptoms should not cause concern. Lasso or Dual controls annual grasses and pigweed and can help control nutsedge and black nightshade. These herbicides can be combined with Lexone, Sencor, 14 or Amiben (incorporated or preemergence) and with Lorox (preemergence only) to improve broadleaf weed control. The rate for Lasso is 2 to 4 quarts Lasso 4E or Microtech 4L or 16 to 26 pounds of Lasso II 15G per acre. The rate for Dual 8E is IV2 to 4 pints per acre, and the rate for Dual 25G is 6 to 12 pounds per acre. Use the higher amount for the soil when incorporating or when black nightshade or yellow nutsedge is to be controlled. The rate for combinations is slightly less than that for the herbicide used alone (see labels). Lasso may be applied after soybean emergence but before soybeans pass the unifoliolate stage. Amiben (chloramben) can control annual grasses and many broadleaf weeds in soybeans when used at the full rate. Do not expect control of cocklebur or annual momingglory. Control of velvetleaf and jim- sonweed is often erratic. Amiben occasionally injures soybeans, but usually the damage does not affect yield. Injured plants may be stunted and have abnormal, shortened roots. If rain does not occur within 3 to 5 days of an Amiben preemergence application, a rotary hoe should be used over the field. Amiben is best suited to soils that have more than 2. 5 -percent organic matter. Amiben can be applied alone or with Dual, Lasso, or Prowl as a preplant incorporated or preemergence treatment. Amiben plus Sencor can also be mixed with Lasso, Dual, or Prowl as a preplant or preemergence treatment. An\iben can be applied as a preemergence treatment with Lorox, Lexone, or Sencor. The broadcast rate for Amiben alone is 20 to 30 pounds of lOG, 4 to 6 quarts of 2S, or 2.4 to 3.6 pounds of 75DS per acre. The Amiben rate in com- bination is 3 to 6 quarts of 2S (1.8 to 3.6 pounds of 75 DS) per acre. Use the higher rate where black nightshade, velvetleaf, or common ragweed is a prob- lem weed. Sencor or Lexone (metribuzin) can be applied any time during the 2 weeks before planting and can be incorporated with Command, Dual, Lasso, Prowl, Son- alan, or Treflan. Incorporation should distribute the herbicide evenly throughout the top 2 inches of soil. Sencor or Lexone can be applied preemergence by itself or with Amiben, Dual, Lasso, Prowl, or Surflan. Sencor or Lexone can control many annual broadleaf weeds but does not control annual momingglory. Con- trol of giant ragweed, jimsonweed, and cocklebur is marginal at the reduced rates necessary to minimize soybean injury. Accurately adjust rates according to soil conditions. Do not apply to sandy soil that is low in organic matter. Combinations allow for reduced rates and thus reduce risk of soybean injury. The combination rate of Sencor or Lexone is one-half to one pint of 4L or one-third to two-thirds pound of 75 DF. You can use higher amounts as a split preplant and preemergence appli- cation. The higher amounts can improve broadleaf control but also increase the risk of soybean injury. One symptom of soybean injury is yellowdng (chlo- rosis) of the lower leaves at about the first-trifoliolate stage or later; it may be followed by browning of leaves and death of plants, depending upon the se- verity of the injury. Seedling diseases, weather stress, and atrazine carryover may increase the possibility of soybean injury. Injury may be greater on soils with a pH over 7.5. Accurate, uniform application and in- corporation are essential. Some soybean varieties are more sensitive than others. Injury has sometimes oc- curred when organophosphate insecticides such as Thimet, Counter, Dyfonate, Lorsban, or Mocap were left in applicators used for com planting and were applied to soybeans that were then being treated with metribuzin. Turbo SEC (metolachlor plus metribuzin) is a formulated mixture (9:2 ratio) with 6.55 pounds of metolachlor and 1 .45 pounds of metribuzin per gallon. The rate is IV2 to 3V2 pints per acre, depending on soil texture and organic matter. Scepter (imazaquin) is formulated with 1.5 pounds active ingredient per gallon. The use rate is two-thirds pint or one-eighth pound of active ingredient for all methods of application — including preplant incor- porated, preemergence, postemergence, and in the various combinations. Approved tank-mix combina- tions include Prowl, Treflan, Sonalan, Lasso, or Dual. For systems with little or no tillage, it may be used -with Prowl, Lasso, or Dual; and Gramoxone, Roundup, or Bronco may be added. It is preferable to use another herbicide with Scepter to improve grass control. Broadleaf weeds controlled by Scepter include pigweed, lambsquarters, smart- weed, jimsonweed, and common ragweed. Scepter can give relatively good control of cocklebur and may help on bur cucumber. Incorporation is recommended to improve control of velvetleaf and giant ragweed. Scep- ter may provide partial control of ivyleaf and tall momingglories. Although labeled for postemergence use, primarily for control of pigweed and cocklebur, primary emphasis in Illinois will likely be soil-applied use. Scepter may be soil-applied v^thin 30 days before planting or at planting but before crop emergence. Rainfall is relatively important for good performance. Initial labeling has indicated a waiting period of 4 months before planting small grain and 11 months before planting com or grain sorghum. Research on persistence in the soil suggests that uniform and ac- curate applications are important. Under certain weather or climatic conditions, excessive rates on field ends and lack of uniformity may result in some effect on sensitive crops (such as com) the following season. Do not apply Classic, Preview, or Lorox Plus the same year as Scepter because of possible additive residual effects. Modown (bifenox) can control pigweed, lambs- quarters, and smartweed and can provide some control of velvetleaf. Modown 4F rates are 2V2 to 4 pints per 15 pecially from preemergence use followed by cold, wet soil conditions during early growth stages. Injury symptoms are cupping and crinkling of the first few leaves. Usually, soybean injury is not reflected in yield. Furloe Chloro IPC (chlorpropham) can be preplant incorporated with Treflan or Vernam; or it can be applied preemergence by itself or with Lasso to im- prove smartweed control. Preplant application should be done within a few days of planting soybeans, and incorporation should distribute the herbicide uniformly throughout the top 1 to 2 inches of soil. The rate in sequential or tank-nux combinations is 2 to 3 quarts of Furloe 4E per acre. Furloe 20G is used preemergence at 10 to 15 pounds per acre. Preview (metribuzin plus chlorimuron ethyl) is a premix herbicide formulated as a 75 -percent dry flow- able in a ratio of 1 part chlorimuron ethyl to 10 parts metribuzin. It can be used preemergence in combi- nation with Lasso, Dual, or Prowl or preplant incor- porated into the top 1 or 2 inches of soil with a dinitroaniline herbicide such as Treflan or acetanilides such as Lasso or Dual. In systems with little or no tillage. Preview can be used preemergence to soybeans and postemergence to small weeds with the addition of 0.25 -percent nonionic surfactant or one quart of crop oil as a burndown treatment. Preview can be applied with Roundup, Gramoxone, or Bronco for added postemergence weed control. Preview controls a wide range of broadleaf weeds, including velvetleaf, cocklebur, jimsonweed, sun- flower, pigweed, common ragweed, lambsquarters, and smartweed. Momingglory, giant ragweed, and black nightshade are controlled only partially. Preview can be used on soils with pH of 7.0 or less with organic matter between 0.5 and 5.0 percent. Rates range from 6 to 10 ounces per acre, depending on soil texture. When Preview is used, attention should be given to crop rotational plans. Wheat may be grown 4 months after Preview applications; but com recropping is restricted to 10 months and sorghum to 12 months if normal rainfall occurs. Consult the Preview label for complete recropping information. Preemergence herbicides Lorox or Linex (linuron) is best suited to silt loam soils that contain 1- to 3-percent organic matter. Do not apply to very sandy soils. Linuron controls broadleaf weeds better than grass weeds. It does not control annual momingglory, and control of cocklebur and jimsonweed is variable. Accurate and uniform appli- cation and proper rate selection are necessary to min- imize the risk of crop injury. Tank-mix combinations allow the use of a reduced rate of linuron to decrease the risk of soybean injury, but this reduced rate may also decrease the degree of weed control. Linuron is registered in tank-mix combinations with Amiben, Lasso, Dual, Prowl, or Surflan to improve grass control. The rate of linuron in these combinations is 1 to P/a pounds of linuron 50DF or 1 to 1% pints of linuron 4L on silt loam soils that have less than 3- percent organic matter. Surflan (oryzalin) can control annual grasses, pig- weed, and lambsquarters if rainfall is adequate. You should rotary hoe to control emerging weeds if ade- quate rain does not fall within 7 days after application. Surflan can be used as an early preplant application for no-till soybeans. Do not use on soils that have more than 5 -percent organic matter. The rate is 1 to 2 pounds per acre of Surflan 75W (% to IV2 quarts AS, aqueous suspension) used alone or % to 1 Va pounds of Surflan 75W in combinations. Surflan is also avail- able as an 85DF. Surflan can be tank-mixed with Amiben, Lorox, Lexone, or Sencor, to improve control of broadleaf weeds. Surface application may be made within 2 days after planting, prior to emergence. Surflan may cause stem callusing, which can lead to soybean lodging. Do not allow Surflan to contact the soybean seed. For no-till soybeans, Surflan can be applied in fall or early spring over undisturbed stubble from the previous crop. When combined with 2,4-D, it may be applied prior to 30 days before planting. Prowl (pendimethalin) may be applied preemer- gence in combination with Amiben, Lorox, Lexone, or Sencor. When appUed to the soil surface. Prowl may cause stem callusing, which can lead to soybean lodg- ing. (For more information, see the subsection about preplant herbicides.) Lorox Plus (linuron plus chlorimuron ethyl) is a 60-percent, premixed, dispersible granule formulation with linuron and chlorimuron ethyl in a 16:1 ratio. Lorox Plus can be used preemergence in combination with Lasso or Dual or following preplant incorporated applications of grass control herbicides such as Treflan or Prowl. Use in the Midwest should be restricted to soils with pH of 6.8 or lower and with V2- to 3 -percent organic matter. Consult the label for further infor- mation on soil restrictions. Lorox Plus controls a variety of broadleaf weeds including cocklebur, velvetleaf, jimsonweed, pigweed, common ragweed, and smartweed. Control of annual momingglory, giant ragweed, and sunflower is partial. Before using Lorox Plus, consider crop rotational plans. In the Midwest, wheat may be grown 4 months after applications of Lorox Plus, corn or sorghum after 10 months, if Lorox Plus is applied before June 15. Consult the Lorox Plus label for complete information on rotational cropping restrictions. Postemergence herbicides Research suggests that soybean yields will probably not be reduced if weeds are controlled within 3 to 4 weeks after the soybeans are planted. Postemergence herbicides are most effective when their use is part of a planned program and when they are applied while the weeds are young and tender; they should not be considered simply as emergency treatments. It is es- pecially important to use timely treatments when using 16 postemergence herbicides in narrow-row soybeans. Postemergence herbicides have been helpful for con- trolling some problem weeds such as cocklebur, annual morningglory, and volunteer corn. It is important to know what specific weeds are present in the field and the size of those weeds. Select herbicides and rates accordingly. Usually, smaller weeds are easier to con- trol. Registered combinations are shown in Table 4. For more information about conditions affecting apphca- tion, see the section entitled "Postemergence herbicide principles" and refer to labels. Basagran (bentazon) can control many broadleaf weeds, such as cocklebur, jimsonweed, and velvetleaf; but it is weak on pigweed, lambsquarters, and annual morningglory. It can be used at higher rates for control of yellow nutsedge and Canada thistle. It does not control annual grasses. The suggested rate for Basagran is three-fourths to one quart per acre, depending on the weed size and species. Specifics on weed size and rates are indicated on the label. Application, however, preferably should be made when weeds are small (no more than 2 to 3 inches tall) and actively growing. These conditions usually exist when the soybeans are in the unifoliolate to second-trifoliolate stage or within 2 to 3 weeks of planting. Spraying during warm, sunny weather can also improve performance. Do not spray if rain is expected within 8 hours. Use a minimum of 20 gallons of water per acre and 40 psi spray pressure to get complete weed coverage. Adding a crop-oil concentrate to Basagran may increase performance on most weeds but may cause some soybean injury. Morningglory that is up to 10 inches long can be controlled with the addition of 2 fluid ounces of 2,4-DB (Butyrac 200) with Basagran. Do not add crop oil when mixing with 2,4-DB. Do not nux or apply Basagran with other pesticides or liquid fertilizer except as specified on the product label. A 28-percent UAN (urea ammonium nitrate) solu- tion — commonly referred to as 28-percent nitrogen solution — may be added to the spray mixture instead of crop-oil concentrate for improved velvetleaf control. The UAN solution may be added to the tank with Basagran plus Blazer when velvetleaf is the primary target weed. Do not use brass or aluminum nozzles Table 4. Registered Postemergence Herbicide Com- binations for Broadleaf Weed Control in Soybeans Amiben Basagran Blazer 2,4-DB Alanap ... X — — X Amiben — X X Basagran — X X Blazer ... X X X Classic — — X Tackle ... — X — X X = Registered — = Not registered when spraying Basagran and 28-percent nitrogen so- lution. Basagran may be applied as a spht application of one pint plus one pint per acre. Apply the first pint of Basagran before weeds reach the maximum size or leaf stage as indicated on the label. Make the second application of one pint 10 to 14 days after the first application. Blazer or Tackle (acifluorfen) should be applied when broadleaf weeds are in the 2- to 4 -inch stage and actively growing. Weeds controlled include annual morningglory, pigweed, jimsonweed, and black night- shade. Cocklebur and morningglory control can be improved with the addition of 2 fluid ounces of 2,4- DB. Apply the mixture when cocklebur and morning- glory measure no more than 10 or 12 inches. Surfactant addition is recommended when combining Blazer and 2,4-DB, but not with Tackle plus 2,4-DB. The rate is 2 pints of Blazer 2L or Tackle per acre. Blazer requires the addition of a nonionic surfactant at a minimum of 1 pint per 100 gallons of spray. Use of surfactant is also recommended with Tackle. The rate of surfactant may be increased to 2 to 4 pints per acre to improve control of small escaped grasses. Because Blazer and Tackle are contact herbicides, leaf bum often occurs; however, the crop usually recovers within 2 to 3 weeks. With Blazer, do not spray if rain is expected wdthin 6 hours; with Tackle, do not spray if rain is expected within 4 to 6 hours. Basagran plus Blazer or Tackle provides a means of broadening the spectrum of control because Blazer or Tackle is better on pigweed and annual morning- glory, while Basagran is better on cocklebur. The rate is 1 to 2 pints of each product in the combination. Addition of an adjuvant (crop-oil concentrate or sur- factant) is suggested. To improve velvetleaf control with Blazer plus Basagran, one quart of 10-34-0 liquid fertilizer or 28-percent nitrogen solution at labeled rate can be used to replace the surfactant or crop-oil concentrate (COC). Do not add COC when using 10- 34-0 or 28-percent nitrogen solution. A mixture of Blazer plus Basagran plus 2 fluid ounces of the amine formulation of 2,4-DB can be used to improve control of cocklebur and morningglory under dry weather conditions. Do not add COC or any other additives when using 2,4-DB vdth Basagran plus Blazer. Refer to individual product labels for specifics. Classic (chlorimuron ethyl) is formulated as a 25- percent dispersible granule for spraying in a minimum of 10 gallons of water per acre postemergence. It can be applied from after crop emergence to 60 days before soybean maturity. Aerial application is not included on initial labeling. The rate is one-half to three-fourths ounce of product per acre, equivalent to one-eighth to three-sixteenths ounce active ingredient. Do not exceed one ounce per season if more than one appli- cation is made. Classic can control pigweed, cocklebur, smartweed, jimsonweed, common ragweed, and common (w^ld) 17 sunflower. It can also help to control m^leaf mom- ingglor\-, tall momingglor\', and yellow nutsedge. It should be applied when most weeds are 2 to 4 inches tall, but when momingglories and giant ragweed are 1 to 2 inches tall. It can be applied to common sunflower up to 8 inches tall and to cocklebur up to 12 inches tall. Control of velvetleaf is weak; and it does not control lambsquarters, prickly sida, or venice mallow. Control of black nightshade is questionable, and Classic does not appear to control bur cucumber. Another herbicide should be programmed for control of grass weeds, and provision for control of lambs- quarters should be considered. A surfactant at 0.25 percent by volume should be used with Classic. Apply within 24 hours of mixing; and, if the mixture is allowed to settle during this time, re-agitate well. Classic may cause some tempo- rary yellowing and retardation of soybean growth, ^\^th these effects generally most e\ident 5 to 7 days after application to soybeans under stress. Conditions that put weeds under stress, such as cultivation, may decrease effectiveness. Do not apply Classic if rain is expected within 4 hours. Determine soil pH before applying Classic, and do not apply to soils with a pH over 6.8. Do not plant wheat within 3 months after application of Classic; do not plant com or sorghum within 9 months. If Classic is applied after August 1, do not plant com the next season and do not plant sorghum within 11 months. If Classic is used following Preview or Lorox Plus, the inter\-al before planting com or sorghum will be extended. Be certain that the correct rate of Classic is applied ver}' uniformly because the residual from excessive rates may affect subsequent crops, such as com. Classic may be tank-mixed with Blazer according to label instructions. Do not mix with any other crop production chemicals except as directed by the label. If Scepter is used the same season as Classic, do not recrop (except to soybeans) within 18 months of the last herbicide application. When com injury occurs, it may be evident when corn is 8 to 10 inches tall, with some stunting and color change. Amiben (chloramben) can be used for postemer- gence application on soybeans in the cracking to fourth-trifoliolate stage, but only within 33 days after planring. This treatment can be especially helpful in controlling velvetleaf; but smartweed, common rag- weed, and pigweed may also be controlled or sup- pressed. Velvetleaf may be 1 to 8 inches tall, and the others may be 1 to 3 inches tall. For ground applica- tions, 10 to 20 gallons of water per acre, a spray pressure of 30 psi, and flat-fan nozzle tips are sug- gested. The rate of Amiben 2S alone is 6 quarts; it is 5 to 6 quarts per acre in combination with either 2 to 3 fluid ounces of Butyrac 200, 2 to 3 quarts of Alanap, or 1 V2 to 2 pints of Blazer per acre. Crop-oil concentrate should be used at one quart per acre with the Amiben alone or tank-mixed with Alanap. Do not add crop oil when tank-mixing with But\Tac. The Amiben plus Alanap or 2,4-DB should be applied when soybeans are in the third- to sixth- trifoliolate stage. Apply the Amiben tank-mixed with Blazer at the appropriate rate for the weed size indicated on the Blazer label, but within 33 days after planting. If Amiben is also soil- applied, do not use more than a total of 12 quarts per season. Rescue (naptalam plus 2,4-DB) can be used for midseason to late-season postemergence control of cocklebur, giant ragweed, and wild sunflower; it may also suppress annual momingglorv'. Apply 3 quarts per acre after soybeans are about 14 inches tall or after first bloom. The addition of a crop-oil concentrate or surfactant can improve control. Application before the weeds flower is suggested for best control. The water volume per acre is 10 to 25 gallons for ground appli- cation and a minimum of 5 gallons for aerial appli- cation. If rain occurs within 6 hours, effectiveness may be reduced. Activity may not be very noticeable until 10 to 14 days after application; maximum activity should occur 20 to 30 days after application. Crop injury such as leaf twisting and terminal droop may occur. To avoid possible yield losses, do not apply Rescue to soybeans under stress from drought, disease, or injur}' from another herbicide. Do not apply Rescue within 60 days of harvest. Poast (sethoxydim) can be used for postemergence control of annual and perennial grasses in soybeans. The rate is one pint per acre to control foxtails or most other annual grasses that are 3 to 8 inches tall. Apply one-half pint per acre when wild proso millet is 4 to 10 inches tall. For control of volunteer cereals as tall as 6 inches, apply IV: pints per acre before tillering. Poast is not recommended for spring control of vol- unteer cereals that emerged the previous fall. Wirestem muhly up to 6 inches tall can usually be controlled by a single application of IVi pints per acre. Poast can also be used as a rescue treatment for controlling selected annual grasses. Apply Poast at a rate of IV: pints per acre for control of actively growing foxtails or seedling johnsongrass (up to 16 inches tall), fall panicum or bamyardgrass (up to 12 inches tall), and crabgrass or goosegrass (up to 8 inches tall). For control of actively growing wild proso millet up to 24 inches tall, apply Poast at one pint per acre. The addition of ammonium sulfate in the spray solution at IVi pounds per acre may improve grass control. Use high-quality, readily soluble ammonium sulfate to avoid plugging spray nozzles. Components of the tank-mixture should be added slowly, with agitation, in the following sequence: (1) ammonium sulfate, (2) crop-oil concentrate, and (3) Poast. After use, rinse the entire spray system with water to reduce corrosion. Use 5 to 20 gallons of spray solution per acre for ground application and a minimum of 5 gallons per acre for aerial application. Note that the lower appU- cation volumes often result in more consistent control 18 of grass weeds. Use only standard high-pressure hol- low-cone or flat-fan nozzles, with pressure at the nozzle adjusted to a minimum of 40 psi and a maxi- mum of 60 psi. Always add crop-oil concentrate at 2 pints per acre. Do not cultivate within 5 days before Poast application or within 7 days after apphcation. Poast can be tank-mixed with Basagran, provided the Poast rate is increased by 50 percent to compensate for the reduced grass control that often occurs with this treatment. Sequential applications at least 24 hours apart may be more economical and practical, depend- ing upon the weeds to be controlled and their size. Do not apply Poast if rainfall is expected within 1 hour. Do not apply Poast to grasses under stress from hot, dry weather or herbicide injury. Blazer may be tank-mixed with Poast (Blazer label) for postemergence control of broadleaf and annual grass weeds in soybeans. For fall panicum and giant foxtail that are 3 to 8 inches tall, the rate per acre is iy2 to 2 pints of Blazer plus 1 pint of Poast plus 2 pints of crop-oil concentrate. For other annual grasses listed on the Poast label, increase the rate of Poast by 50 percent. Sequential applications should always be used instead of the tank-mixtures for perennials and may be more economical for many annuals. Fusilade 2000 (fluazifop) can be used for post- emergence control of annual and perennial grass weeds in soybeans. And it is very effective on volunteer corn. Apply only to actively growing grasses before they tiller. The rate is IV2 pints per acre when giant foxtail is 2 to 6 inches tall and other annual grass weeds are 2 to 4 inches tall. Use % pint per acre when volunteer corn is 12 to 24 inches tall, shattercane is 6 to 12 inches tall, or wild proso millet is 6 to 12 inches tall. For control of volunteer cereals, apply 1 pint per acre before plants are 2 to 6 inches tall. To control wirestem muhly, apply IV2 pint per acre when plants are 4 to 12 inches tall. Fusilade can also control johnsongrass and quackgrass, but sequential applications may be needed. (See the section entitled "Specific weed prob- lems.") The spray volume should be a minimum of 10 gallons per acre for ground application and 5 gallons per acre for aerial application. Add either crop-oil concentrate at one percent by volume (1 gallon per 100 gallons of spray) or a nonionic surfactant at 0.25 percent of spray volume. For aerial application, add one pint of crop-oil concentrate or surfactant per acre. Apply before soybeans bloom. Do not tank-mix Fusilade with other postemergence herbicides intended for control of broadleaf weeds, except as specified. A tank-mix of Fusilade 4E and Blazer 2L is labeled for use without an increase in the Fusilade rate. Roundup (glyphosate) can be applied through sev- eral types of selective applicators — recirculating sprayers, wipers, or rope wicks. This application is particularly useful for control of volunteer corn, shat- tercane, and johnsongrass. Roundup may also suppress hemp dogbane and common milkweed. Weeds should be at least 6 inches taller than the soybeans. Avoid contact with the crop. Equipment should be adjusted so that the lowest spray stream or wiper contact is at least 2 inches above the soybeans. For equipment calibration, refer to the Roundup label. For recirculating sprayers and wipers, use the rates given on the label. For rope-wick applicators, mix 1 gallon of Roundup in 2 gallons of water. A spot treatment with Roundup is also a good option in many fields. For apphcation made on a spray-to- wet basis, use a 1- to 2-percent solution of Roundup in water. For motorized spot treatments in which coverage of weeds may be less than complete, use a 5-percent solution. Avoid contact of the spray with the soybeans. Add a dye for increased visibility. Gramoxone harvest aid Gramoxone is registered for drying weeds in soy- beans just before harvest. For indeterminate varieties of soybeans (most varieties planted in Illinois), apply when 65 percent of the seed pods have reached a mature brown color or when seed moisture is 30 percent or less. For determinate varieties, apply when at least one-half of the leaves have dropped and the rest of the leaves are turning yellow. For the new formulation of Gramoxone Super with 1.5 pounds active ingredient per gallon, the rate is 11 to 21 fluid ounces per acre. Use the high rate on cocklebur. The total spray volume per acre is 2 to 5 gallons for aerial application and 20 to 40 gallons for ground application. Add 1 quart of nonionic surfactant per 100 gallons of spray. Do not pasture livestock within 15 days of treatment; and remove Uvestock from treated fields at least 30 days before slaughter. Specific weed problems Yellow nutsedge Yellow nutsedge is a perennial sedge with a trian- gular stem. It reproduces mainly by tubers, which begin sprouting about May 1 in central Illinois. For the most effective control, soil-applied herbicides should be incorporated into the top 2 inches of the soil. For soybeans, a delay in planting until late May allows time for two or three tillage operations to destroy many nutsedge sprouts. These operations help deplete food reserves in nutsedge tubers. Row cultivation is helpful. Preplant incorporated applications of Dual, Lasso, or Reward will also help. Lasso (alachlor) preplant incorporated at IV2 to 4 quarts per acre can often give good control for nut- sedge. Dual (metolachlor) can be applied at 2 to 3 pints per acre to control nutsedge. Preplant incorporated treatment is preferred to treatment at the preemergence stage. 19 Reward 6E (vernolale) applied preplant at 4 pints per acre is effective against yellow nutsedge. Immediate incorporation is necessary with Reward. Basagran 07611132011) applied postemergence can also help control nutsedge in soybeans. When nutsedge is 6 to 8 inches tall, three-fourths to one quart per acre can be applied. If needed, a second application can be made 7 to 10 days later. The addition of a crop-oil concentrate to Basagran improves perfor- mance. For corn that is planted relatively early, preplant tillage before nutsedge sprouts is of little help in control. Timely cultivation gives some control, but a program of herbicides plus cultivation has provided the most effective control of nutsedge. Several preplant treatments are available. Eradicane Extra at SVa to 8 pints or Eradicane, Sutan+, or Genate Plus at 4% to 1% pints per acre is effective for control of yellow nutsedge in com. These products must be incorporated immediately. Lasso or Dual applied in com as for soybeans can also be quite effective.' The combinations of Lasso, Dual, Sutan-t-, Genate Plus, Eradicane, or Eradicane Extra incorporated with atrazine may improve control of nutsedge while also controlling broadleaf weeds. Atrazine or Bladex (cyanazine) may be used as a postemergence spray to control emerged yellow nut- sedge when it is small. Split apphcations of atrazine plus oil have been more effective than single appli- cations. Basagran may be used in com in a manner similar to that for soybeans. Lorox or Linex (linuron) as a directed postemergence spray has also given some control. Johnsongrass Johnsongrass can reproduce both from seeds and by rhizomes. Both chemical and cultural methods are needed to control johnsongrass rhizomes. Much of the rhizome growth occurs after the john- songrass head begins to appear. Mowing, grazing, or cultivating to keep the grass less than 12 inches tall can reduce rhizome production significantly. Control of johnsongrass can also be improved with tillage. Fall plowing and disking bring the rhizomes to the soil surface, where many of them are winter-killed. Disking also cuts the rhizomes into small pieces, mak- ing them more susceptible to chemical control. Johnsongrass rhizomes can be controlled or sup- pressed with the use of certain herbicides in various cropping programs. Several herbicides can provide control of johnsongrass seedlings in soybeans or com. (See the table at the end of this guide.) Treflan (trifluralin) or Prowl (pendimethalin) used in a 3-year soybean program has been fairly successful in controlling rhizome johnsongrass. Either can be used at IV2 to 2 times the normal rate each year for 2 years; in the third year, either they are used at the normal rate or another suitable herbicide is used before a regular cropping sequence is resumed. Thorough preplant tillage and incorporation are necessary for satisfactory control. Be certain not to plant crops such as com or sorghum the year following application of these herbicides at the higher rates. Fusilade 2000 (fluazifop) can control johnsongrass in soybeans. Apply IV2 pints per acre when the weed is 8 to 18 inches tall. Apply before the boot stage of growth. If new shoots or regrowth occurs, make a second application of one pint per acre when john- songrass is 6 to 12 inches tall. Add crop-oil concentrate at 1 percent of volume or add nonionic surfactant at 0.25 -percent volume. Poast (sethoxydim) can control johnsongrass in soybeans. Apply IV2 pints of Poast plus 1 quart crop- oil concentrate per acre when the johnsongrass is 15 to 25 inches tall. Use of ammonium sulfate at 2V2 pounds per acre, in addition to the crop-oil concentrate with Poast, and use of low spray volume of 5 to 10 gallons per acre are suggested for best control. If regrowth or new growth occurs, apply one pint per acre when the johnsongrass is 6 to 12 inches tall. Eradicane Extra can help control rhizome johnson- grass in com when used at a rate of 8 pints per acre with a tillage program; or Eradicane 6.7E can be used at 7V3 pints per acre. Roundup (glyphosate) can be used as a spot treat- ment to control johnsongrass in com, soybeans, or sorghum. Apply a 1 -percent solution when johnson- grass has reached the boot to head stage and is actively growing. Use of Roundup in rope-wick applicators or recovery-type sprayers is effective for control of john- songrass in soybeans. (See the section entitled "Her- bicides for soybeans," the subsection about post- emergence herbicides.) Roundup may be apphed in small-grain stubble when johnsongrass is in the early head stage. Fall applications should be made before the first frost. At least 7 days should be allowed after treatment before tillage. Quackgrass Quackgrass is a perennial grass with shallow rhi- zomes. In Illinois, it is found primarily in the northern part. Atrazine is quite effective when used as a split application in com. Apply 2 quarts of atrazine 4L per acre in the fall or spring and plow 1 to 3 weeks later. Another 2 quarts per acre should be applied as a preplant or preemergence treatment. Postemergence application is usually less effective. A single treatment with 3 to 4 quarts per acre can be applied either in the spring or fall 1 to 3 weeks before plowing, but the split application usually gives better control of annual weeds. Use equivalent rates of other formu- lations. If more than 3 pounds of atrazine active ingredient is applied per acre, plant no crops other than corn or sorghum the next year. 20 Eradicane Extra can be used to suppress quackgrass in corn if more flexibility in cropping sequence is desired. A rate of SVs pints per acre of Eradicane Extra can be used on light infestations, while 8 pints per acre is suggested for heavier infestations. Some risk of injury to corn occurs, especially at the higher rate. A tank-mix with atrazine should improve control. If Eradicane 6.7E is used, the rate range is from 4% to 7V3 pints per acre. Fusilade 2000 (fluazifop) may be used for quack- grass control in soybeans at IV2 pints per acre. Apply when quackgrass is 6 to 10 inches tall. If regrowth occurs, a second application of one pint per acre may be made. Best results are obtained with Fusilade and most other treatments if rhizomes are cut up by preplant tillage to stimulate maximum emergence of grass shoots. Always add crop-oil concentrate or non- ionic surfactant to Fusilade. Poast (sethoxydim) may be applied in soybeans at the rate of 2V2 pints plus 1 quart of crop-oil concentrate per acre when quackgrass is 6 to 8 inches tall. If regrowth occurs or new plants emerge, apply 1 ¥2 pints per acre when the quackgrass is 6 to 8 inches high. Roundup (glyphosate) may be used for controlling quackgrass before planting corn, sorghum, or soy- beans. Apply 1 to 3 quarts per acre when quackgrass is 8 inches tall and actively growing (fall or spring). For annual cropping systems, apply 1 quart per acre in 5 to 10 gallons of spray with surfactant added. Delay tillage for at least 3 days after application. Wirestem muhly Primarily, wirestem muhly is a problem in northern and western Illinois. A perennial, it reproduces by seeds and scaly rhizomes. These rhizomes are often moved by chisel plows, field cultivators, and shovel cultivators. Many farmers report that delayed seedbed preparation, where possible, can provide some control of wirestem muhly; but wirestem muhly does not start growth until late spring. Roundup (glyphosate) can be used early preplant (early June) or after harvest when wirestem muhly is at least 8 inches tall and actively growing. Do not till before fall or spring applications. The rate is 1 quart of Roundup in 5 to 10 gallons of water per acre, with surfactant added at 2 to 4 quarts per 100 gallons. Use flat-fan nozzles. After applying, wait 3 days before tilling. Atrazine at high rates may provide a little help on wirestem muhly in corn. Rates must be at the highest labeled rates for soil. (See the subsection about quack- grass.) Fusilade (fluazifop) may be used postemergence to control wirestem muhly in soybeans. The rate is IV2 pints per acre when wirestem muhly plants are 4 to 12 inches tall. Poast (sethoxydim) may also be used postemer- gence in soybeans to control wirestem muhly that is 6 inches tall. The rate is IV2 pints per acre. Addition of ammonium sulfate at V-li pounds per acre and a low spray volume of 5 to 10 gallons per acre are suggested to improve control. (See the section entitled "Herbicides for soybeans," the subsection about post- emergence herbicides, for more information about Poast and Fusilade.) Canada thistle Canada thistle is a perennial weed that has large food reserves in its root system. Canada thistle has several varieties, which differ not only in appearance but also in their susceptibility to herbicides. 2,4-D may give fairly good control of some strains. Rates will depend on where the thistle is growing. For example, higher rates can be used in grass pastures or in noncrop areas than can be used in com. Banvel (dicamba) often is a little more effective than 2,4-D and may be used alone or in combination with 2,4-D. Banvel can be used as an after-harvest treatment in wheat, com, or soybean fields or in fallow fields. Rates vary from 1 to 2 quarts of Banvel alone or in tank-mix combinations with 2,4-D or Roundup. Fall treatments should be applied before killing frosts. For best results, thistles should be fully emerged and actively growing. Fields treated in the fall with Banvel may be planted to com, sorghum, or wheat the next season. Atrazine and oil applied postemergence has been fairly effective in controlling Canada thistle in com. Make the application before thistles are 6 inches tall. Basagran (bentazon) can be used for control of Canada thistle in soybeans or corn when the thistles are 8 to 12 inches tall. Apply three-fourths to one quart per acre in a single application; or, for better control, make two applications of three-fourths to one quart per acre each, 7 to 10 days apart. Roundup (glyphosate) can be used at 2 to 3 quarts per acre when Canada thistle is at or beyond the early bud stage. Fall treatments must be applied before frost for best results. Allow at least 3 days after apphcation before tillage. Black nightshade Increasingly, black nightshade has become a prob- lem for Illinois soybean growers. The berries, which are about the same size as soybeans at harvest, contain a sticky juice that can gum up a combine. Black nightshade can be controlled more easily in corn than in soybeans. Herbicides such as atrazine, Bladex, Banvel, Lasso, and Dual are helpful for con- trolling this weed in com. If possible, plant suspect fields to com rather than to soybeans. If soybeans are planted, plant suspect fields last so that the herbicide is more nearly at full strength when nightshade seed germinates. For control in soybeans. Lasso, Dual, Amiben, or 21 Table 5. Relative Effectiveness of Herbicides on Major Weeds This table gives a general comparative rating. Under unfavorable conditions, some herbicides rated good or fair may give erratic or poor results. Under very favorable conditions, control may be better than indicated. Type of soil is also a very important factor to consider when selecting herbicides. Rate of herbicide used also will influence results. G = good, F = fair or variable, and P = poor. Grasses Broadleaf weeds 8 "3 •a <8 S 3 u 'c ngrass lings or tercane E o 01 T3 3 C o c 2 o < 3 J3 2 Si « 3 1 ■§ •o c o e o u 01 c 'So 73- T3 t: e C/5 2 o> 1 'S >< & CO to x> 2 U <0 a. Johnso seed Shat c 3 1 5 _o 1 U c o tn e e -J 2 0) 60 (0 Of 0 C 3 CD > 1 SOYBEANS Prelant Command G c G-F G G F F F P F G G P P F-G p G P G Treflan, Sonalan F-G G G G G G F P P-F P P G P-F G P p P-F P P Sencor, Lexone + dinitroaniline F G G G G G F P F F F-G G P G G F G F F-G Vemam, Reward F G G G G G P-F F P-F P P F P G P P P P F Preplant or preemergence 1 Amiben F-G G F-G F-G F-G F P P P P P-F G F-G G F-G F F-G P F Lasso, Dual G. G G G G P-F P F-G P P P F F-G G P-F P P-F P P Lasso or Dual + Sencor or Lexone F G G G G P P F P F F-G G F-G G F F G F F-G Lasso or Dual + Lorox,', Linex' F G G G G P P P-F P F F G F-G G G F G F F Lorox,' Linex' F F F F F P P P P F F G F G G F G F F-G Surflan,' Prowl F-G G G G G G F P P-F P P G P G P P P-F P P-F Scepter G F-G F F P-F F F F F G G G F-G G G F-G G G F-G Scepter + Prowl, Treflan, or Sonalan G G G G G G F F F G G G F-G G G F-G G G F-G Scepter + Lasso or Dual G G G G G F F F-G F G G G G G G F-G G G F-G Sencor, Lexone F F F F F P P P P F F-G G P G F-G F G F F-G Postemergence Basagran F-G P P P P P P F P-F G G F-P P P F F G G F-G Blazer, Tackle F P-F P P-F P P P P F-G F G F-P F-G G F-G F-G G F P-F Classic F-G P P P P P P F F G G P P G G F-G G G F 2,4-DB P-F P P P P P P P F-G G P-F F P F F F P F P Poast, Fusilade G G G G G G G P P P P P P P P P P P P Rescue F-G P P P P P P P F G F P-F P F-G P G P G P ' Do not use for preplant incorfX>ration. linuron at full rates or a combination of Amiben or linuron with Lasso or Dual is helpful. Scepter can also be effective. Suspect fields should be monitored and a postemergence application of Blazer considered. Blazer 2L at 2 pints per acre can control nightshade when applied at the 2- to 4 -leaf stage. Tackle is also effective. Harvest-aid sprays generally do not solve the prob- lem because they do not make the berries fall before the soybeans are harvested. Additional information Not all available herbicides and herbicide combi- nations are mentioned in this guide. Some are relatively new and are still being tested. Some are not considered to be well adapted to Illinois or are not used very extensively. For additional information about field crop weed control, consult your county Extension adviser or write to the Department of Agronomy, University of Illinois at Urbana-Champaign, N-305 Turner Hall, 1102 South Goodwin Avenue, Urbana, Illinois 61801. 22 Table 5. Relative Effectiveness of Herbicides on Major Weeds (continued) Grasses Broadleaf weeds c f= a3 in o »-■ nl C ^^ nj (0 tx re c 60 D. o X ^ ns ^ o ns ns U fi CQ U tu i« o 01 c ns I/) ns ^^ S O ^ 2 J2 O' 2 o V F bO 73 o u 01 in ;-i 3 01 C 01 C ^ a O a 01 > > D X) 01 o U T3 01 01 c o ^ u (0 2 JH 01 ^ a; ns XI 3 (0 cr JS tf) U) S 00 01 o; bO o E ^ , i c ns u 00 ■a ■T3 0) V 01 CORN Preplant Butylate, EPTC F-G G G G G F-G F-G P P P P-F F G P P P P F Butylate, EPTC + atrazine, Bladex F-G G G G G F-G F-G F-G F-G G G G G G F G F-G F-G Princep + atrazine G F-G F-G F F P-F P F-G F-G G G G G G G G G F Preplant or preemergence Atrazine G F-G F P P P F G F-G G G G G G G G G F-G Bladex F-G F-G F-G F-G G P P F F-G G G G F G F-G G F-G F-G Bladex + atrazine F-G F-G F F F-G P P F-G F-G G G G G G F-G G F-G F-G Lasso, Dual F-G G G G G P-F F-G P P P F F-G G P-F P P-F P P Lasso or Dual + atrazine or Bladex F-G G G G G P F-G F-G F G G G G G F G F-G F Prowl + atrazine or Bladex' F G G G G F P F-G F G G G G G F G F-G F-G Ramrod' G G F F-G F P P-F P P P F P G P P P P P Postemergence Atrazine + oil F-G F-G G P P P F G G G G G G G F G G G Banvel F-G P P P P P P G G G G G G G G G G F Basagran G P P P P P F P-F G G F-P P P F F G G F-G Bladex F-G G G F F-G P F F F-G G F G F-G G F G F F-G Buctril, Brominal F-G P P P P P P G G G G G F G F G F-G F Tandem + atrazine G G G F P P F G G G G G G G G G G G 2,4-D F P P P P P P G G F G F G G G P-G G F-G Do not use for preplant incorporation. 23 January 1987 University of Illinois; with the assistance o RexLieb A^ss°s?a^ pVof.tnr of^"^ Anderson, Extension Assistant, all at the Kapusta, Professor of Plant and Soil SciencrSoutLrn iMnni^^^ of Agronomy at the University of Illinois, George of Agriculture, Western Illinois UniverLfy This'gulde s ba^^^^^ ""' ^^--^^^ "^^'^^^P- P^o^^^so" USDA, and Professor of Weed Science and E W sfoMpfpilnf dh ^ ? research conducted by Loyd A. Wax, Agronomist the University of Illinois. Issued mfurtheranc^ of (Sonpr^^^^^ '"^ Professor of Agronor^y, both at cooperation with the U.S. DepartmenT^fTgnculture XuA^^^ ^L^^^ ' ^"^ j'ne 30. 1914. in University of Illinois at Urbana-Champaign The II Lis Co^^lr.ti^?o r^ 0"'^''^°''' Cooperative Extension Service, programs and employment. ^ ^ Cooperative Extension Service provides equal opportunities in 24