PUBLICATION No. 83 Published by direction of HONOURABLE L. C. HALMRAST Minister of Agriculture A. M. WILSON Field Crops Commissioner R. M. PUTNAM Deputy Miniter The Alberta Advisory Weed Committee is composed of representa- — University of Alberta, Edmonton — Canada Dept, of Agriculture, Lethbridge, Lacombe, Beaverlodge, Fort Vermilion — Alberta Department of Agriculture, Edmonton Alberta Field Supervisors' Association. Chemical Trade — Canadian Agricultural Chemicals Association The following members of the Alberta Advisory Weed Committee contributed in the preparation and the editing of this publication : Dr. A. C. Carder, Experimental Farm, Beaverlodge. Dr. W. G. Corns, Department of Plant Science, University of Alberta, Edmonton. H. A. Friesen, Experimental Farm, Lacombe. J. J. Sexsmith, Research Station, Lethbridge. W. Lobay, Field Crops Branch. tives of the following agencies : Department of Plant Science Experimental Farm Service Field Crops Branch A. W. Goettel, Field Crops Branch. INDEX Page Selective Herbicides - 5 Recommendation for Chemical Weed Control in Cereal Crops 8 Weed Classification 10 Weed Control in Grass and Legume Crops - 12 Soil Sterilant Chemicals 13 Other Herbicides 14 Control of Woody Growth * 15 Gontrol of Weeds in Pastures and Non-crop land ....16 Weed Control in Specialty and Horticultural Crops 17 Machines for Application of Chemicals 19 Calibrating a Field Sprayer 20 Care and Maintenance of Spraying Equipment 21 Precautionary Measures When Using Herbicides 22 FOREWORD This bulletin is published by the Department of Agriculture with the view to bringing farmers up to date on the latest chemical weed control recom- mendations. Many selective herbicides are very effective in controlling particular weeds when used accord- ing to approved methods, but they may be equally destructive if carelessly handled. The Department of Agriculture therefore urges farmers to follow specific recommendations. Chemicals for weed control must not be considered as substitutes for good farming methods. Many different chemicals are offered for sale and those who use them in growing crops should be very familiar with the recommendations in order to obtain maximum results from their use. A. M. WILSON, Field Crops Commissioner. WEED CONTROL WITH CHEMICALS By W. LOBAY AND A. W. GOETTEL Field Crops Branch Alberta Department of Agriculture SELECTIVE HERBICIDES 2.4- D — 2,4-dichlorophenoxyacetic acid 2,4-D is available in three formulations: Ester, Amine and Sodium Salt. It is obtainable in various strengths, usually in 64, 80 or 128 ounces of acid equivalent per Imperial gallon. The weed killing property of 2,4-D formulations is based on the active ingredient or acid equivalent content. The ester forms have been more widely used than amines or sodium salts. Esters are quicker acting and are less affected by rain, they are more effective on hard-to-kill weeds and usually require lower dosages for comparable results. Amine and sodium salt forms are preferable on the more sensitive crops as flax and legumes. MCPA — 2-methyl-4-chlorophenoxYacetic acid MCPA is a growth regulator type of weed killer, somewhat similar to 2,4-D and is also available in the three formulations — Ester, Amine and Sodium Salt. MCPA is generally less harsh to crops than 2,4-D. It has a wider safety margin and may be applied at earlier or later stages of growth of cereal crops without danger of loss. The sodium salt of MCPA may be used for controlling weeds in peas, alfalfa, clovers, since this form is not as injurious to these crops. MCPA ester provides somewhat better weed control than the MCPA amine or sodium formulations. 2,4,5-T — 2,4,5-trichlorophenoxyacetic acid 2,4, 5-T is used mainly for the control of woody growth where species resistant to 2,4-D are present. These include wild rose, dog- wood, hawthorn, ash, bearberry, blackberry and raspberry. Usually a mixture of 2,4-D and 2,4,5-T is as effective as 2,4,5-T alone and less costly. There is no advantage in using 2,4,5-T for weed control. See the section on "Control of Woody Growth”, page 15. 2.4- DB and MCPB — 4-(2,4-dichlorophenoxy) butyric acid 4-(2-methyl-4-chlorophenoxy) butyric acid These chemicals commonly called the "butyrics” are quite similar to 2,4-D and MCPA, however certain legume crops are tolerant to the butyrics which make them useful in crop rotation programs. Many weeds which are susceptible to ordinary 2,4-D are also susceptible to the butyric herbicides, but higher rates of chemical are required for similar results. The butyric herbicides applied at 16 ounces per acre will give very effective top growth control of Canada sow thistle in cereal crops and seedling legume crops. (See the section on "Weed Control in Grass and Legume Crops,” page 12.) 5 Low Volatile Esters of 2,4-D, MCPA, etc. The low volatile esters of 2,4-D, MCPA and 2,4,5-T are similar to the standard esters with respect to selectivity and toxicity on annual weeds and crops. Under some conditions the low volatile forms are more effective on hard-to-kill weeds. The danger of damaging suscep- tible crops in adjoining fields is reduced by using low volatile forms since less vapors or fumes are given off by the chemical. The low volatile forms are, however, usually somewhat slower acting than the standard esters. Dust forms 2,4-D is also available in the dust form. One of the advantages of using 2,4-D in the dust form is where water is difficult to obtain. Dusts should be applied at about IV2 times the rate of sprays (acid equivalent) making application more costly and the danger of drift to nearby crops more likely. Sprays are generally more effective on hard-to-kill weeds than are dusts. When to Treat One of the most important factors in selective chemical weed control is early treatment of weeds. Weeds offer severe competition to crops in their early stages of growth by reducing tillering or stool- ing. Chemical treatment should be timed to eradicate weeds while they are still young and before they have damaged the crops. Most weeds, even the most susceptible, are more easily killed when young. However, it is not always possible to treat when the weeds are young because crop damage may result. Choice of 2,4-D or MCPA The safety of the crop to be treated and the amount and kinds of weeds present determine the use of 2,4-D or MCPA. 2,4-D may be used safely at recommended rates on wheat, barley or rye. Oats and flax should be treated with MCPA. However, if very weedy conditions exist in oats and flax or weeds resistant to MCPA are present, then 2,4-D amine or ester should be used. MCPA may be used on wheat or barley where weed growth makes it advisable to treat before 3 to 4 leaf-stage of the cereal crops. The use of MCPA is also advisable when cereal crops are under- Select proper chemical for the seeded with legumes^^ (See "Weed weed and crop. Control in Legume Crops.") MCPA is generally less harsh to crops than 2,4-D and somewhat slower acting. Cne should consult Tables 2 and 3 on pages 10 and 11 respectively to determine whether MCPA or 2,4-D should be used in specific cases. While crop injury may occur from use of these chemicals it will often be offset by a higher relative yield from a less weedy crop. 6 The weeds present in untreated crops would usually result in greater reduction of yield than will the effects of the higher rates of chemicals. WHEN TO USE CHEMICAL SPRAYS 2,4-D TREATMENT GUIDE FOR WHEAT, BARLEY, RYE DON'T TREAT JOINTING SAFE TO TREAT DON'T TREAT TREAT MCPA TREATMENT GUIDE FOR FLAX T TWO LEAF DON'T TREAT For use of 2.4-D. See section on "Flax". f 4 or 5 LEAF GROWING SAFE TO TREAT BUD FLOWERING DON'T TREAT This chart reproduced by kind permission of Line Elevator Farm Service, Winnipeg. Rates to Apply The rotes of application of 2,4-D or MCPA required to effectively control weeds in crops depend upon the predominant weeds present, their stage of growth and climatic conditions. Weeds are classified into five groups on the basis of sensitivity or resistance to 2,4-D and MCPA. (See Tables 2 and 3 on pages 10 and 11.) Effective control of weeds in crops depends largely on using the proper dosage for the weeds in question and applying this at an early stage of growth. See Table 2 on page 10 for "Weed Control Recom- mendations in Cereal Crops". The lower rates of application for each of the five groups are recommended where ideal spraying conditions exist. The higher rates are recommended where : (1) Spraying is done during advanced growth stages of the weed. (2) Conditions are dry (3) Crops are heavily infested with weeds. 7 Table I indicates the quantity of herbicide required to treat 10 acres with various concentrations of chemical at certain dosages per acre. TABLE 1 — QUANTITIES OF HERBICIDE REQUIRED TO TREAT 10 ACRES AT VARIOUS RATES OF APPLICATION. Ounces of 2,4-D or MCPA Acid Number of Pints of 2,4-D or MCPA to Treat 10 Acres Per Gallon as Specified on Container Rate of Application of 2,4-D or MCPA Acid in Ounces per Acre 2 3 4 5 6 7 8 9 10 12 16 24 32 48 56 2.9 4.3 5.7 7.2 8,6 10 11.4 12.8 14.3 17.2 22.8 34 45 68 64 2.5 3.9 5 6.2 7.5 8.7 10 11.2 12.5 15.0 20 30 40 60 76 2.1 3.2 4.2 5.2 6.3 7.4 8.4 9.5 10.5 12.6 16.8 25 33 50 80 2 3 4 5 6 7 8 9 10 12 16 24 32 48 96 1.6 2.5 3.3 4.1 5 5.8 6.6 7.5 8.3 10 13.3 20 26.6 40 128 1.2 1.9 2.5 3.1 3.7 4.3 5 5.6 6.2 7.5 10 15 20 30 NOTE: — This chart can be used for 2,4-D or MCPA. Drift Hazard Certain precautions must be observed when using 2,4-D or MCPA. Spray, dust or vapor drift may damage nearby sensitive crops, such as flowers, many vegetables, trees, shrubs, legumes and specialty crops such as rape and sugar beets. The following are worthy of consideration when treating crops near susceptible vegetation : (1) Use a boom sprayer, not an aircraft, boomless or dusting machine. (2) Use the amine or sodium salt or low volatile ester formula- tion. (3) Keep the pressure low, not over 30 pounds per square inch. (4) Do not apply herbicides on windy days. RECOMMENDATIONS FOR CHEMICAL WEED CONTROL IN CEREAL CROPS Wheat and Barley The growth of these crops can be divided into four developmental periods, during which the plants respond in a different way to 2,4-D. These periods are : 1. Emergence to 3-leaf — this is a highly susceptible period when re-action to 2,4-D is expressed in leaf and spike deformities. Use the correct amount of chemical. 8 2. 3-leaf expanded to early flag-leaf (shot-blade) stage — this is a relatively tolerant period; applications of 2,4-D or MCPA for weed control should be made during this period. 3. Flag-leaf (shot-blade) to fully headed — a highly susceptible period when 2,4-D causes a high degree of sterility. 4. Milk stage to full maturity — a highly resistant period. At the susceptible stages (see 1 and 3) MCPA is safer to use on wheat or barley than is 2,4-D. If the weed species present are sus- ceptible to MCPA and spraying is done during these susceptible stages, it would be better to substitute MCPA for 2,4-D. Oats Oats is more susceptible to 2,4-D than wheat or barley and considerable damage frequently occurs if 2,4-D is used. 2,4-D is therefore not recommended in oats except under special conditions, such as the presence of Russian thistle or scentless mayweed. If 2,4-D is used the least damage to the oat crop will occur if treatment is made with an amine formation during the periods from emergence to the 2-leaf stage and between the 6-leaf and flag-leaf stages. Since oats have proved tolerant to MCPA at all growth stages, this herbicide can be applied as soon as weed conditions warrant. Winter Wheat and Rye These crops may be treated in the early spring with 2,4-D or MCPA at the rates recommended for spring-sown grain. Treatment is not recommended during the fall or in late spring when the crop has reached the shot-blade stage. Flax Flax may be treated with 2,4-D or MCPA from the time the plants reach a height of 2 inches up to just before the prebud stage of growth. To obtain best results this crop should be treated as soon as there is enough emergence of susceptible weeds to make it prac- tical. There may be some reduction in yield from flax treated with 2,4-D or MCPA unless weed competition is reduced enough to com- pensate for any injury resulting from the treatment. Flax is more tolerant to MCPA than 2,4-D. The use of MCPA is preferable except when control of the more resistant weeds is required. In this case 2,4-D ester should be used and some damage to the flax accompanied by delay in maturity should be expected. 9 TABLE 2 — RATES OF 2,4-D AND MCPA RECOMMENDED AS SPRAYS ON WHEAT, OATS, BARLEY, RYE, CORN (Not under-seeded with legumes) Ounces Acid Equivalent Per Acre. CROP Formulation Weed Group I Weed Group 11 Weed Group 111 Weed Group IV Weed Group V 2, 4-D Wheat, barley. Ester 3 to 4 4 to 6 6 to 8 (9 to 12) (12 to 16) rye and corn Amine 4 to 5 5 to 7 7 to 9 (10 to 14) (15 to 20) *Oats (in em- ergency cases) Amine 4 to 5 5 to 7 (7 to 9) *Flax Ester 3 to 4 (4 to 6) (6 to 8) Amine 4 to 5 (5 to 7) (7 to 9) MCPA Oats (wheat. Ester 3 to 4 4 to 6 6 to 8 (9 to 12) (12 to 16) barley, rye and corn) Amine Sodium 4 to 5 5 to 7 7 to 9 (10 to 14) (15 to 20) Salt 5 to 6 6 to 8 8 to 10 (11 to 15) (15 to 20) Flax Ester 3 to 4 4 to 6 (6 to 8) (9 to 12) Amine 4 to 5 5 to 7 (7 to 9) (lOto 14) Sodium Salt 5 to 6 6 to 8 (8 to 10) (12 to 15) * For emergency use only. Considerable reduction in crop yield can be expected particularly where the rates in parentheses are used. Note: — The higher rates in the first three weed groups are recom- mended if spraying is delayed until the weeds have reached an advanced stage of growth, under drier conditions, and where crops are heavily infested with weeds. The rates in parentheses, ( ), are higher than those considered safe for these crops, and should be considered if weeds belonging to weed group IV or V are present. Although these rates are likely to cause a reduction in crop yield this will frequently be offset by obtain- ing a higher relative yield from a less weedy crop. Note the safe spraying period mentioned above. Where the above chemicals are applied in a dust carrier it is generally advisable to use up to one-third more acid per acre than the rate recommended in a water spray. TABLE 3 — WEED CLASSIFICATION ACCORDING TO RESPONSE TO 2,4-D AND MCPA. Group I — Very susceptible. Wild Mustard 10 Group II — Susceptible annuals (require higher dosages than Group I). Lamb's quarters Indian Mustard Common Ragweed Stinkweed Ball Mustard Tumbling Mustard False Ragweed Sunflowers Hare's Ear Mustard Wormseed Mustard Great Ragweed Group III — Moderately susceptible. (Susceptible in early growth stages. May become less susceptible under adverse conditions and/or advancing growth), Blue Burr Cocklebur Goatsbeard Stinging Nettle Wild Radish Burdocks Dandelion (in lawns) Gumweed Russian Pigweed Shepherd's Purse Sweet Clover Flixweed Prickly Lettuce Common Plantain Group IV — Moderately resistant. (Under adverse conditions and/or with advancing growth become resistant.) Perennials require retreatment. Prostrate Amaranth Field Bindweed Common Chickweed Curled Dock Spear-leaved Goosefoot Dog Mustard Red-root Pigweed Quickweed Perennial Sow thistle Russian thistle Hedge Bindweed Tartary Buckwheat Hoary Cress Western False Flax Common Groundsel Tansy Mustard Pineapple Weed Smartweeds Canada thistle Tumbleweed Wild Buckwheat Tall Buttercup Dandelion (in fields) Large Seeded False Flax Blue Lettuce Peppergrass Purslane Annual Sow thistle Prairie thistle Biennial Wormweed Group V — Consists mainly of perennial weeds of which generally only the top growth is controlled with 2,4-D or MCPA. Creeping Buttercup Horsetail Russian Knapweed Scentless Mayweed Hemp Nettle Leafy Spurge GROUP RESISTANT TO 2,4-D AND MCPA (Control impossible or impractical with these chemicals) Bladder Campion Night-flowering Catch- fly Purple Cockle Shield Cress Knotweed Milkweed Tansy Bracken Shrubby Cinquefoil White Cockle Ox-eye Daisy Wild Licorice Poverty Weed Yellow Toad flax Cacti Cow Cockle Corn Spurry Grasses Stinking Mayweed Pasture Sage Y arrow 11 TABLE 4 — WOODY GROWTH CLASSIFICATION Group I — Controllable by 2,4-D. Hazelnut Manitoba Maple Balsam Poplar Spirea Chokecherry Pincherry Saskatoon Willows Currants Honeysuckle Lilac Aspen Poplar Western Snowberry Wolf Willow Group II — Not Controllable by 2,4-D. Blackberry Rose Oak Raspberry Group III — Apparently more susceptible to 2,4, 5-T than to 2,4-D. WEED CONTROL IN GRASS AND LEGUME CROPS Alfalfa and Clovers These legumes are most resistant at an early stage of develop- ment (about the second true-leaf stage). Fields should not be treated unless the legume stand is vigorous and dense and is seriously infested with weeds. Generally there is very little damage to grass seedlings in grass-legume mixtures. Sweet Clover should not be treated with 2,4-D, 2,4-DB, MCPA or MCPB at any stage of development. Where sweet clover is present as a vigorously growing stand with a companion crop, spraying would only be justified on the basis of severe competition from susceptible annual weeds. Under these conditions, MCPA amine at 3 to 4 ounces per acre would appear advisable. Grain crops under-seeded with alfalfa and/or red, white and alsike clovers can be treated to kill susceptible weeds with 2,4-D or MCPA amine at 3 to 4 ounces or with the sodium salt of MCPA at 3 to 6 ounces of acid per acre. Selective dinitro compounds (DNBP) may be used at 20 to 24 ounces of acid in 80 gallons of water per acre. The large amount of water (80 gallons) per acre has limited the use of dinitro products. Where red, alsike or ladino clovers are present, MCPB ("MCP butyric") or a mixture of MCPA-MCPB (1:15) at 16 - 20 ounces of acid equivalent per acre in 20 gallons of water can be used. Where alfalfa is present, 2,4-DB ("2,4-D butyric") at 16 - 20 ounces per acre in 20 gallons of water can be used. The butyric herbicides should be applied at the first true trifoliate leaf stage of the clover or alfalfa and when the weeds are young. Weeds which can be controlled with the butyric herbicides are wild mustard, lambs' quarters, common ragweed, stinkweed, pigweed, Canada thistle and perennial sow thistle. Early germinating annual weeds such as Russian pigweed can be effectively controlled in established stands of alfalfa before growth Ash Dogwood Rose Bearberry Hawthorn Caragana Blackberry Raspberry 12 starts in the spring using 2,4-D or MCPA ester at 8 to 16 ounces per acre. Treatment delayed until alfalfa growth is one inch high should be at reduced rates (4-6 ounces). No treatment is recommended after the alfalfa is 4 inches tall. When established pastures contain a high proportion of red, alsike or ladino clovers, Canada and sow thistle can be effectively controlled without serious injury to these legumes by applying MCPB at 24 ounces of acid in 20 gallons of water per acre. Treatment should be made when the thistles are at their most susceptible stage, i.e., in early bud. Grasses Susceptible annual weeds have been eliminated with no apparent damage to seedling stands of brome, creeping red fescue and crested wheat-grass by the use of 2,4-D ester at 8 ounces per acre when the grass is over 4 inches high. Crested wheat-grass appears less suscep- tible to 2,4-D than brome-grass. In established stands of brome, there is evidence of seed yield reduction when 2,4-D ester is applied at rates of over 2 ounces per acre just prior to heading. With creeping red fescue, indications are that 2,4-D ester up to 4 ounces per acre or 2,4-D amine up to 8 ounces per acre will not reduce the seed yield when applied at any stage of growth up to the time of heading. SOIL STERILANT CHEMICALS A soil sterilant is a chemical that is applied to the soil to prevent plant growth for a number of years. Use of such chemicals is only practical on limited areas where a high expenditure is justified to control persistent weeds that can not be effectively controlled by other means. Soil sterilants have been used mainly in the eradication of small patches of persistent perennial weeds such as toad flax, leafy spurge, hoary cress, Russian knapweed, couch grass and field bind- weed. They may also be used to control vegetation around buildings, fences, yards, etc. Soil sterilants may be applied at any time during the growing season but best results are obtained with spring or fall applications. (For information on their application, see Publication No. 80, "Suggestions for the Use of Soil Sterilants''.) CAUTION: — Do not use soil sterilant chemicals near or under desirable trees or shrubs. Sodium Chlorate Sodium chlorate and compounds containing this chemical have been used as weed killers for many years. Applied at rates from 2 to 4 pounds per 100 square feet, sodium chlorate is quite effective as a spray solution or spread dry on the soil. In sandy or alkali soils the rate of application should be higher. Since sodium chlorate presents a fire hazard, it should be handled with care at all times. 'The fire hazard is somewhat reduced if the chemical is applied in the dry form. Sodium chlorate should not be used near buildings or combustible materials. When mixed with water or organic materials such as dust, shavings, etc., it is a highly combustible material and may explode upon ignition. 13 Chlorate-Borate Mixtures These mixtures combine the rapid action of sodium chlorate with the persistent toxicity of the borates and they do not present a fire hazard. They are usually in the form of a powder which necessitates spray application. These mixtures are sold as Polybor Chlorate, Chlorax — for examples, and should be used at the rates of 3 to 4 pounds per 100 square feet. Borates These herbicides are non-inflammable and may be used safely around buildings. Grasses are somewhat tolerant to borates at the lower rates. The most common borate available in Alberta at present is Concentrated Borascu. Spring application is preferred at the rates of 4 to 6 pounds per 100 square feet for the control of deep-rooted perennial weeds. Borate herbicides are usually sold in a granular form. Monuron (CMU) Monuron is a very effective long-term soil sterilant which is non-inflarnmable and non-poisonous to animals, but it may irritate the skin. It will usually keep the soil free of vegetation for several years particularly of grasses. It is most easily applied as a spray in enough water to provide complete coverage at rates of 2 to 3 ounces per 100 square feet. This chemical is sold as Karmex W and Telvar W. Monuron is also one of the active ingredients in Chlorea and Ureabor which are applied in granular form at rates of 1 to 4 pounds per 100 square feet. Borate — 2,4-D Mixtures This mixture is sold as D. Bor Granular. It is a non-poisonous granular material which will effectively control persistent perennial weeds such as toad flax, leafy spurge, etc. Applied dry at rates of 2 to 4 pounds per 100 square feet, it will control persistent perennial weeds and be selective to grasses depending on the rate applied and the type of soil. This treatment will allow for quick regrowth of grass to compete with any seedling weeds which may appear. OTHER HERBICIDES Sodium TCA — trichloroacetic acid Sodium TCA is used for the eradication of patches of couch grass and for this purpose should be applied at the rate of 80 to 100 pounds active ingredient per acre (3-4 ounces per 100 square feet). Tillage before application followed by a thorough cultivation within about two to three weeks following application is best. When used in this way 1/2 fo 2/3 of the above rates is usually more effective than the higher rates without cultivation . TCA is applied as a spray by dissolving one pound of powder in one gallon of water, however less difficulty is encountered during application if one pound is dissolved in IV2 gallons of water. The application of the chemical must be uniform. Early application (about June 1st) is preferable. The soil will be sterile for two to three months; however in dry years, the residual effect may extend into the next growing season. Green Foxtail Control — The use of TCA at rates of 4 to 6 pounds in 10 - 12 gallons of water per acre will control green foxtail (wild 14 millet) in flax, rapeseed and field peas, but should not be used in cereal grains or canning peas. The chemical should be applied in the early stages of growth preferably from seeding to four-leaf stage of the flax. Other weeds susceptible to 2,4-D or MCPA may be controlled in the same spraying operation by merely adding 2,4-D or MCPA at the desired rate to the TCA mixture. On sugar beets, pre-emergence treatment is most effective. Dalapon Dalapon is a grass-killer somewhat similar to TCA. For the eradication of couch grass lower rates are required (1 ounce per 100 square feet or 20 to 30 pounds per acre) than are required with TCA. Dalapon is applied as a spray to the foliage when in rapid growth, and thorough tillage two or three weeks following application (or when the leaves turned brown) will increase the effectiveness of the chemical. The residual effect of Dalapon on the soil is usually about one month. Dalapon may be substituted for TCA for the control of green foxtail, however the rate of application should be 12 to 24 ounces per acre. Amitrol (amino-triazole, ATA) Sold as Weedazol, Amizol, etc., this herbicide is a white, water soluble powder containing 50% active ingredient. Following its application of this chemical, the leaves of plants turn white due to the loss of chlorophyll. At rates of 6 to 8 pounds per acre active in- gredient, this herbicide combined with cultivation has given fair control of Canada thistle on fallow or non-crop land; however, there is usually sufficient carry-over of the material in fine-textured soils to reduce crops yield in the year following application. Simazine — 2-chloro-4,G-bis(ethYlamino)-S-triazine Simazine is a recently developed herbicide which has shown effective control on a large number of broad-leaf and grass-type weeds, At rates of 10 to 20 pounds (active ingredient) per acre, it is an effective soil sterilant on such weeds; however, higher rates appear to be necessary on deep-rooted perennials. It is available as a 50 per cent wettable powder. Avadex and Carbyne — See Publication No. 144 on "Chemical Control of Wild Cats" for information on the use of these new herbicides. CONTROL OF WOODY GROWTH Woody growth can be quite effectively controlled along road- ways, telephone and power lines, irrigation and drainage ditches or on pasture land with herbicides. In many instances the use of 2,4-D or a mixture of 2,4-D and 2,4,5-T is less costly and gives more permanent eradication than when removed by hand or heavy me- chanical equipment. The susceptibility of woody growth to 2,4-D varies considerably; however, woody growth such as willow and poplar are quite susceptible. These species are the most common. (See Table 4 on page 12 on the classification of Woody Plants accord- ing to susceptibility to 2,4-D and 2,4,5-T.) 15 Best results are obtained when the growth is young. Older growth requires application of more chemical and carrier than does young growth in order to obtain satisfactory control. When growth is tall, spraying will not necessarily produce the desired result and cutting becomes unavoidable. If it is necessary to cut tall growth, the stump can be treated with a mixture of 2,4-D or 2,4-D plus 2,4,5-T in diesel oil to eliminate or minimize regrowth. A mixture of 24 ounces total acid in 10 gallons of diesel oil is recommended to be applied to the point of run-off to the stump and protruding roots. Two methods of woody growth control are commonly used: 1. Foliage Spray — Spraying is done with a water solution pre- ferably soon after the leaves are fully expanded (late May — early lune). The use of 2,4-D ester or, when 2,4-D resistant species are present, a 2:1 mixture of 2,4-D:2,4,5-T is recommended at the rate of 2 to 4 pounds (32 to 64 ounces) total acid per acre in 15 or pre- ferably more gallons of water per acre (sufficient to wet foliage thoroughly). Mixtures of 2,4-D and 2,4,5-T may be purchased as “brush kill”, It is advisable to check the ratio of 2,4-D to 2,4,5-T when purchasing this chemical. If application is by aircraft, 5 to 10 gallons of water or diesel oil per acre may be sufficient. Higher rates of application will be required if growth is heavy or dense. These rates should be satis- factory for controlling brush up to 6 feet high. The addition of 5 to 10 pounds of polybor chlorate and 1 pound of household detergent per 100 gallons of spray solution has given increased brush control. The detergent acts as a “wetting or spreading agent”. Thorough coverage of all growth is required. Retreatment the following season is usually necessary to kill any regrowth or remaining growth missed during the first spraying. 2. Dormant Spray — Spraying is done during the absence of foliage, late fall and early winter. Diesel oil at 10 to 15 gallons per acre must be substituted for the water carrier. The same rates and mixtures of herbicide should be used as for foliage spraying. A mixture of 2,4-D and 2,4,5-T is recommended for dormant spraying. The ratio of 2,4-D to 2,4,5-T should be varied according to the suscep- tibility of the vegetation being treated but generally should not exceed 2:1. Dormant spraying has certain advantages including extension of the spraying seasons into the winter months, easier penetration of heavy growth and reduction of the hazard of destroying nearby sensitive crops. CONTROL OF WEEDS IN PASTURES AND NON-CROP LAND Systemic herbicides can be used for weed and brush control on native pastures, waste land, summerfallow and on cultivated pastures in which there are no legumes. Spraying should be done early in the summer when growth is young and on brush, when the plants are in full leaf. Western snowberry or "buckbrush" commonly found in native pastures and ranges should be treated with 2,4-D ester at 2 to 4 pounds (32 - 64 ounces) in 15 or more gallons of water per acre fairly early in the season. If other woody growth resistant to 2,4-D is encountered one-third of the chemical should be 2,4,5-T. Some 16 regrowth of snowberry may occur necessitating a second but lighter application the second year. Pasture sage may be controlled with 2,4-D ester at 1 to 2 pounds (16 - 32 ounces) in 5 to 10 gallons of water per acre early in the growing season for best results. Silver and big sage brush can be controlled with IV2 fo 2 pounds of acid in 10 gallons of water per acre. Apply the chemical during active growth, preferably early in the growing season. Poisonous weeds such as water hemlock, larkspur, death camas and locoweeds may become a problem when other vegetation is in short supply. They may be controlled by application of 2,4-D at 2 to 3 pounds per acre from the early growth to early bud stage. Sufficient water is necessary for thorough coverage of the vegetation to insure satisfactory results. Repeat applications are usually required for eradication. These above weeds are usually found in areas inaccessible to ground spraying equipment thus making hand or knapsack sprayers necessary. Non-crop land — The application of esters of 2,4-D or MCPA ester on fallow and non-crop land at 16 ounces of acid per acre or the butyl ester of MCPB (butyric) at 32 ounces per acre is a very effective method for removing or controlling the top growth of many broad- leaved annual and perennial weeds. This treatment can be used in lieu of part of the tillage on summerfallow. Normal spring cultivation operations are recommended to destroy annual weeds and volunteer grain. The fallow land is then left until perennial weed growth such as thistles are in the bud stage before spraying at the above rates. Cultivation should be resumed in about 3 to 4 weeks or when regrowth appears. This operation is particularly advisable when time is limited or when too many cultivations may leave the land suscep- tible to erosion. Spraying has the advantage of removing the vegetation without disturbing the soil crust preventing cutworm moths from laying eggs on cultivated fields. WEED CONTROL IN SPECIALTY AND HORTICULTURAL CROPS The use of chemicals for the control of weeds in horticultural crops should be looked upon as a supplement to good cultural practices. However, the cost of weeding many crops may be greatly reduced by the use of herbicides. Since many of the horticultural crops are highly- sensitive, especially to the hormone chemical compounds, ex- treme precautions are necessary to avoid injury from the use of herbicides. To minimize injurious effects, the sodium and amine salt formulations of 2,4-D and MCPA are strongly recommended for use in areas near sensitive crops. (For controlling wild oats in sugar beets, sunflowers, etc., see publication No. 144, "Chemical Control of Wild Oats''.) Sugar Beets Specialty Crops Pre-emergence application of potassium cyanamid (KOCN) at 8 to 10 pounds per acre applied just before beets emerge has given 17 control of broad-leaf weeds. Lamb's quarters is not readily killed. Liquid cyanamid at 8 gallons per acre is reported as giving good control of lamb's quarters and shepherd's purse without injury to beets. Apply TCA for the control of green foxtail in sugar beets at 4 to 6 pounds before emergence or delay 2 weeks after emergence. IPC at 4 to 6 pounds per acre applied to the soil surface and disced-in before seeding will control wild oats effectively. Field and Canning Peas For the control of broad-leaved annual weeds, peas may be treated when the vine length is 4 to 8 inches, with the sodium or potassium salt of MCPA at 2 to 6 ounces of acid per acre in as low as 5 gallons of water per acre although a higher spray volume is preferable. The amine salt of MCPA may be used at 2 to 4 ounces in not less than 15 to 20 gallons of water per acre. The sodium salt of MCPB ("MCP butyric") at 16 to 20 ounces per acre in 15 to 20 gallons of spray mixture may be used or the amine or ammonium salt of the dinitrol chemical (DNBP) at 12 to 20 ounces in 75 gallons of water per acre is also recommended. IPC at 4 to 5 pounds per acre is recommended for the control of wild oats. The IPC is applied to the soil surface and thoroughly disced in to a depth of 2 to 3 inches immediately before sowing the peas. Sunflowers Cultural practices — Post emergence cultivations using a drag harrow, rotary hoe or finger weeder will usually give good control of annual weed seedlings. These cultivations should be crosswise to the row and be discontinued after the sunflowers reach a height of 5 to 6 inches. Chemical Control — IPC at 4 to 5 pounds per acre in 5 to 10 gallons water as pre-planting treatment for the control of wild oats has shown promise in trials in Manitoba. Horticultural Crops Asparagus — 2,4-D and MCPA may be used successfully and effectively for the control of broad-leaved weeds in this crop. Amine and sodium formulations are recommended at the rate of IV2 pounds per acre. The asparagus should be lightly cultivated just as the first spears are emerging early in the season and then sprayed. A second cultivation and application may be given at the end of the cutting season. Pre-emergence applications of monuron at 2 pounds per acre will give satisfactory broad-leaf and seedling grass control. DNBP amine at 3 to 41/2 pounds. NPA (Alanap) at 51/2 pounds and CIPC at 6 to 8 pounds have also been used successfully in experimental trials as pre-emergence treatments for control of both broad-leaf weeds and seedling grasses. Beans — Apply 3 to 41/2 pounds of DNBP amine per acre as a pre-emergence spray just before beans emerge. This treatment will control germinating weed seeds for some time after crop emerges. Onions — Potassium cyanamid (KOCN) at 16 to 24 pounds per acre sprayed in 50 gallons of water per acre will control most annual weeds when applied shortly after emergence. 18 Potatoes — Apply DNBP at 3 to 41/2 pounds per acre immediately prior to crop emergence for the control of broad-leaved weeds. The higher rate should be used on peat soil. Where couch grass is a problem, dalapon may be applied at 12 1/2 pounds per acre before tillage in the spring. Good emergence of the grass is necessary for effective control. Dalapon should not be used on White Rose or on red varieties. Sweet Corn — An application of DNBP amine at 3 to 41/2 pounds per acre in at least 30 gallons of water, is effective when applied during the period just before emergence to 1 inch in height. Simazine applied as a pre-emergent spray is also effective for control of weeds in corn. MACHINES FOR THE APPLICATION OF CHEMICALS Equipment used for the application of herbicides include ground boom and boomless sprayers, turbine sprayers, dusters, and aircraft sprayers and dusters. To assist in the selection of equipment, the following outlines the specific purpose for which the various machines have been designed and their limitations: (a) Boom Sprayers — This type has been most widely used in Alberta. The tractor-mounted and trailer type are both satisfactory. The trailer type is usually preferred since more liquid can be carried hence refills are less frequent; however, the initial investment is usually greater. Care in the operation and cleaning of these machines should insure that the flow from each nozzle is uniform and fan-shaped. Such things as correct pressure, height of boom, and constant speed must be carefully watched. A good sprayer should have the following features; 1. Rust-proof tanks which can be cleaned easily. 2. Good mechanical or fluid by-pass agitator. 3. A non-corrosive pump with adequate packing, and capacity to maintain necessary pressure for spraying or for rapid filling of the tank. 4. Filters between tank and pump, between pump and boom, and at each nozzle. 5 A pressure regulator and quick shut-off valve within easy reach of the operator. An automatic pressure regulator may be used. 6. A pressure gauge easily seen by the operator. 7. A motor with oil bath air cleaner, dust-proof magnets and crankcase breather, and adequate reserve power. 8. Strong rust-proof booms which can be adjusted from 16 to 42 inches in height. (b) Boomless Sprayers — Sprayers with multiple type nozzles at the discharge location have been developed to eliminate boom and nozzle problems experienced with the boom sprayers. Tests with boomless sprayers for field spraying have shown that spray pattern across the swath is not uniform and therefore coverage is patchy. This is due to larger droplets needed to carry the spray further and this means fewer drops per acre. Boomless sprayers are subject to 19 producing more drift. While this machine does not give uniform coverage, it does have the advantage of simple operation. This type of sprayer is recommended for roadside spraying or brush spraying in waste land and pastures where a boom-type sprayer would not be maneuverable. (c) Turbine Sprayers — On this type of sprayer a fan-blast sprays chemical up to a width of 50 feet by means of an air stream. This type is preferred for treating growth under fences, along roadsides, ditches and power lines. Uniformity of application in these cases is not of vital importance as the desired result is usually a complete kill of all growth. The principle disadvantage of this type of machine is the high initial cost. (d) Dusters — These machines are used where a suitable water supply is not readily available. Simplicity and speed of operation and less time lost in refilling are some of the advantages of the use of dusters. However, the chief disadvantage of using dusters are the higher chemical costs and the greater hazard of drift damage to susceptible crops. A good duster should have (1) a rain-proof hopper with suitable agitators to insure uniform flow of dust at all times, (2) an impellor that is readily serviced, and (3) a strong boom, adjustable for heights and carried with low-pressure wheels. (e) Aircraft — The application of chemicals by aircraft is essen- tially a contract operation. It permits the treating of large acreages in a short period of time at costs which usually compare quite favour- ably with ground spraying operations. Areas otherwise inaccessible or fields too wet for ground machines can be treated by aircraft. The hazard of drift is somewhat greater by aircraft application. CALIBRATING A FIELD SPRAYER One of the most important considerations in spraying for weed control is using the proper dosage. Sprayers are not always cali- brated properly and the operator can only guess as to the dosage being applied. A simple method of calibration is as follows; 1. Fill the sprayer tank with clean water. 2. Make an accurately graduated stick for measuring the liquid level in the tank. This can be done by draining the tank of water in five-gallon lots and recording the measurements on the stick. Do not paint or varnish the stick. 3. Refill the sprayer tank and spray at the desired pressure and speed for a distance of one-half mile. 4. Determine' the number of gallons of water used. 5. The number of gallons multiplied by I6V2; divided by the length of the boom in feet equals the number of gallons applied per acre. Example : If on spraying one-half mile using a 33-foot boom it was found that 10 gallons of water were used, then the gallons per acre applied at this throttle setting will be ^33^ ^ ~ ^ gallons per acre. 6. For every 5 gallons the tank holds, add the quantity of chemical recommended per acre for control of the weed. 20 CARE AND MAINTENANCE OF SPRAYING EQUIPMENT The following precautions and operating procedures are necessary for satisfactory sprayer operation : 1. Clean water is essential. Some well water, even though it appears clean, may contain fine silt which may damage the pump and nozzles. 2. Avoid operating the spray pump without solution flowing through it. 3. Use only water pump grease in the spray pump bear- ing and use it sparingly, an ex- cess grease tends to plug the nozzles. 4. Do not leave solution in any part of the sprayer if it is not to be used within a few days. 5. Clean filters and nozzle screens daily. Even if the ma- chine is working satisfactory, accumulations of dirt may dam- age the screens. Storage of Equipment 1. Thorough cleaning of all parts of the sprayer at the end of each spraying season is important. Drain the machine, flush with clean water, rinse with a mild alkali such as washing soda, household ammonia (1 cup to each 31/2 gallons of water), or a household deter- gent, then rinse again with clean water. 2. Coat all iron parts exposed to the chemical with a commercial rust inhibitor or light oil. 3. If the sprayer is stored out-doors, rubber hoses and tires should be removed and stored in a cool dark place. 4. Remove nozzles, take apart, thoroughly cleanse and store in light oil. Before using again wash in kerosene or gasoline to remove oil. 5. Remove caps from the ends of booms and stand booms on end to remove sediment. 6. Remove, cleanse and re-assemble filters. 7. If a small gas engine is used, drain fuel tank and carburetor and pour one tablespoon of engine oil through the spark plug hole. Turn motor over by hand to distribute the oil on the cylinder walls. 8. When storing dusters, see that all parts are thoroughly cleaned. Compressed air may be used for this purpose. The fan bearings require inspection and lubrication in some models. 21 PRECAUTIONARY MEASURES WHEN USING HERBICIDES (1) Whenever systemic herbicides, such as 2,4-D, 2,4,5-T, and MCPA are used, there is danger of spray, dust, or vapour drift. There- fore, when such herbicides are used in the vicinity of susceptible crops, gardens, and shrub or tree plantations, suitable precautions should be taken to prevent drift, and the salt forms (sodium or amine) or the low volatile esters should be used. (2) When applied in excessive quantities, 2,4-D and MCPA will kill a very wide range of plants. Warning is therefore given not to apply rates higher than the maximum recommended for the respective crops and weeds, and to be sure that spraying and dusting machines spread the chemicals uniformly. (3) It is recommended that receptacles, containers, and machines used for applying systemic herbicides should not be used for the application of fungicides and insecticides on susceptible crops. If they must be used, thorough cleaning is necessary. Rinse with water containing a small amount of detergent, fill with a weak solution of household ammonia and allow to stand overnight, drain and rinse thoroughly with water. (4) Sodium chlorate is inflammable, but can be used to advantage if proper precautions are taken. Some commercial preparations of sodium chlorate contain fire-retardant materials, and therefore are safer to use. (5) Do not use herbicides where they may contaminate water used for irrigation or drinking purposes. (6) Do not store systemic herbicides close to seeds, fertilizer, insecticides or fungicides, as they may become contaminated by "fumes" or by accidental leakage. CHEMICALS WERfi^ADE TO KILL PLANTS BE SURE THEY KILL ONLY UNDESIRABLE PLANTS 22 3 3286 Additional Bulletins on .. . WEED CONTROL Chemical Control of Couch Gross, Available From Extension Service DEPARTMENT OF AGRICULTURE Edmonton or YOUR DISTRICT AGRICULTURIST Printed by L. S. WALL, Queen's Printer for Alberta, 19 6 0