Q.630.7 I £6C no. 912, rev cop. 3 CENTRAL CIRCULATION BOOKSTACKS The person charging this material is re- sponsible for its return to the library from which it was borrowed on or before the Latest Date stamped below. Theft, mutilation/ and underlining of books are reasons for disciplinary action and may result in dismissal from the University. TO RENEW CALL TELEPHONE CENTER, 333-8400 UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN MAY 0 1 1992 r .»• SEP 2 6 '994 JUL 3 1 P,M When renewing by phone, write new due date below previous due date. 79521 L162 Cso.1 CIRCULAR 912 (REVISED) Crt rV\£ <> Diseases & Insect Pests HDE2STTIiniCA.TIO^T & CONTROL. O/1 ILLINOIS COLLEGE OF AGRICULTURE COOPERATIVE EXTENSION SER VICE IN COOPERATION WITH THE ILLINOIS NATURAL HISTORY SURVEY o lH£Li8i*rt6nt£ JUN - 9 1967 Mlflo J5r M. 5. ZJJVJV e> FT. //. LUCKMANN CONTENTS PAGE General Control Measures. ... 3 Tomato Diseases 5 Damping-Off 6 Collar Rot 7 Hollow Stem 7 Mosaic Diseases 7 Streak Diseases 11 Bacterial Wilt 13 Leaf Roll 13 Bacterial Canker 14 Fusarium Wilt 17 Verticillium Wilt 19 Gray Leaf Spot 20 Early Blight 21 Septoria Leaf Spot 23 Bacterial Spot 25 Leaf Mold 25 Late Blight 27 Buckeye Rot 28 Blossom-End Rot 29 Botrytis Fruit Rot 31 Anthracnose 32 Minor Fruit Rots 33 Injury from 2,4-D 33 Tomato Insects 37 Flea Beetles 37 Tomato Hornworms 38 PAGE Tomato Fruitworms 39 Colorado Potato Beetles. . . .41 Garden Slugs 41 Cutworms 42 Aphids or Plant Lice 43 Whiteflies 44 Nematodes or Eelworms. . . .44 Symphylids 46 Mites 46 Cloudy Spot of Tomato Fruit . 47 Seed Treatment 48 Eradicative Seed Treatments 48 Protective Seed Treatments 49 Soil Disinfestation 49 Fungicides and Insecticides. . .50 Fungicides 50 Insecticides 51 Spray and Dust Schedules. .52 Dosage of Insecticides and Fungicides 52 Spraying and Dusting Equipment 52 Home Gardens 52 Commercial Fields 53 Urbana, Illinois June. l'.K Cooperative Extension Work, University of Illinois, College of Agriculture, and the U. S. Department of Agriculture cooperating. John B. Claar, Director. Acts approved by Congress Maj 8 and .June 30, 1914. Q. £,30-7 (LbfA Tomato Diseases and Insect Pests o o Identification and Control By M. B. Linn and W. H. Luckmann1 TOMATOES now rank as one of the most important truck and garden crops in Illinois. Although they are grown largely for market and canning, sizable plantings can be found in practically every home garden. Like most crops, the tomato is subject to a number of diseases and is attacked by several insects. While not all cause serious losses, there are a number that require definite attention if the crop is to be grown with profit. The information given in this circular is designed for home gardeners, commercial tomato grow- ers, cannery fieldmen, and all others interested in growing tomatoes. GENERAL CONTROL MEASURES In addition to specific control measures for specific troubles, there are several general practices that all tomato growers should follow to keep losses from diseases and insects at a minimum. Select disease-free seed. Saving the seed from only healthy plants and fruit will eliminate many crop losses and much soil contamination that would otherwise occur. Certified seed is of considerable value, for it comes from fields certified by state inspection agencies as being free from bacterial canker and cer- tain other seed-borne diseases. Treat seed. Regardless of the origin of the seed, it should be given an eradicant treatment to insure freedom from disease organisms. Unless the eradicant is one of the very few that also serve as protectants, the seed should be given a protective treat- ment as well. This will reduce losses from seed decay and damping-off in the seedbed. Plant on clean soil. Many serious field troubles start from infested soil in the seedbed. Disease-free soil that has not grown 1 M. B. Linn, Professor of Plant Pathology, and W. H. Luckmann, Ento- mologist, Illinois Natural History Survey. Appreciation is expressed to M. C. Shurtleff who advised on fungicides and disease-resistant varieties. 4 Circular No. 912 tomatoes, potatoes, eggplants, okra, or peppers should preferably be used. If this is not possible, the soil should be disinfested. See that seedbeds are well ventilated. Good ventilation of seedbeds, along with proper spacing and watering of seedlings, will help to prevent seedling diseases. Use only healthy transplants. Diseases and insects are often introduced into gardens and fields on transplants. If you have to buy plants, insist that they be free from these pests. Do not select plants with spots on the leaves, brown lesions on the stems, or knots on the roots if healthy plants are available. Commercial growers should use only certified, disease-free transplants. Ventilate southern-grown plants as soon as received. If you use southern-grown plants, take a few bundles from each hamper or basket on arrival. This will let the air circulate more freely around all the plants and will help to prevent diseases. Ventila- tion is especially important when high temperatures or rains delay setting the plants in the field. (If you dip the roots in water, be careful to see that the stems and leaves are kept dry.) Pay close attention to sanitation. It is much easier, more effective, and less costly to prevent heavy losses from plant pests than it is to control them once they have become established. If you have a small garden where a long rotation is not practical, pull up and destroy all plants that die during the growing season. Do not place these plants on the compost pile, or the disease or insects that killed them may be returned to the garden soil. If you have a large garden or a commercial field, it is advisable to plow under deeply all plant refuse. Also destroy all weeds within or near the tomato plantings since they often harbor certain diseases and insects during the winter. Rotate crops. Most growers have learned by experience that planting the same crop on the same land year after year becomes unprofitable. Once every three years is often enough to plant tomatoes on the same land. Do not rotate them with potatoes, eggplants, okra, or peppers. Keep out of field when plants are wet. Don't walk through the field or cultivate it when the plants are wet with dew or rain. <> () Tomato Diseases 5 This is very important in preventing the spread of such diseases as gray leaf spot, early blight, late blight, and Septoria leaf spot. Watch for first signs of diseases and insect pests. Apply proper sprays or dusts promptly. To control diseases satisfac- torily, it is usually necessary to apply fungicides before the diseases appear. TOMATO DISEASES Tomato diseases are caused by fungi, bacteria, viruses, nema- todes, or unfavorable environmental conditions. Fungi and bacteria are microscopic plants which depend upon green plants such as tomatoes for their food. They enter the tomato plant either through wounds or through the unbroken epidermis. Once inside the plants, they may cause spotting of the leaves or fruit, rotting of the stem, fruit, or roots, and often wilting and death of the entire plant. Fungi and bacteria may overwinter on old tomato vines and fruit, on weeds of the tomato family, and on tomato seed. Viruses are infectious substances too small to be seen with the ordinary microscope although their presence can be demon- strated in several ways. Some tomato viruses are highly infec- tious, that is, easily transmitted from diseased to healthy plants by mere contact. Other viruses are not so easily spread and are transmitted only through the feeding and subsequent plant-to- plant movement of certain insects. Nematodes attacking tomatoes are microscopic, eel-like roundworms that feed on the plant roots. The most common disease caused by nematodes in tomatoes is called root knot. For a discussion of the disease and its control, see page 44. Diseases due to unfavorable environmental conditions are sometimes called noninfectious diseases because they do not spread from one plant to another. Some of the conditions which may cause these troubles are too much or too little soil moisture and nutrients, temperatures above or below the optimum for growth of the tomato plant, and injury caused by incorrect ap- plication of herbicides, insecticides, and fungicides. Circular No. 912 r v < All these tomato seedlings except the one on the left show injury typical of post-emergence damping-off. Note the shriveled stems of the affected seed- lings as compared with the healthy plant. (Fig. 1) Damping-Off Damping-off is common wherever tomato seedlings are grown. Any one of several soil fungi may cause this trouble. There are two types: pre-emergence and post-emergence. The latter type is the one most commonly associated with the term "damping-off." In pre-emergence damping-off the seed rots in the soil or the seed- ling dies before it emerges. In post-emergence damping-off the seedling topples over after it has emerged from the soil but while it is still small and succulent. The plant collapses because the stem tissues at or near the ground level become soft and water-soaked (Fig. 1). Damp, cloudy weather, poor ventilation, and overcrowding and overwatering of the seedlings form ideal conditions for this disease. Control. Soil disinfestation (page 49) is one way to control both pre-emergence and post-emergence damping-off in the hotbed, cold- frame, or greenhouse flat. Seed treatment with a protective fungicide such as captan or thiram (page 49) is also advisable even if the soil has been disinfested. This measure is particularly effective against seed rot. If post-emergence damping-off has caused trouble in the past, water seedlings at 5- to 10-day intervals with a suspension containing captan or zineb (1 tablespoonful per gallon of water) or ziram (2 tablespoonsful per gallon) (page 50). Sprinkle 1 pint of suspension on 12 square feet of seedbed surface. Keep fungicide in suspension by constant agitation. <> o Tomato Diseases 7 Collar Rot This disease, which differs in appearance from damping-off in that the affected stem tissues are somewhat hard and brittle instead of soft and water-soaked, is discussed under "Early Blight" (page 21). Hollow Stem A noninfectious disease, hollow stem may occur in almost any stage of tomato-plant development. However, if care is used in pro- ducing and selecting seedlings, this disease will be of little importance. Control. Do not use spindly transplants. This is the most important single measure for preventing losses from hollow stem. Seedlings should be properly hardened-off before they are set in the field and should not be transplanted into dry soil. Avoid overcrowding, overwatering, and overfertilization with nitro- gen. These factors, either singly or together, may contribute to the appearance of hollow stem. Too little sunlight may also be a con- tributory factor. Mosaic Diseases Mosaic diseases are the most common tomato troubles encountered under Illinois conditions. In fact, most tomato plantings have some degree of mosaic infection before the growing season is over. The seriousness of these diseases is not often recognized, however, for their symptoms are sometimes inconspicuous and the damage they do is usually ascribed to some other cause. At least three mosaic diseases of tomato are known to occur in Illinois: common mosaic, aucuba mosaic, and cucumber mosaic. Com- mon and aucuba mosaics are caused by two strains of the common tobacco-mosaic virus, which also attacks a large number of weeds and economic plants. Cucumber mosaic in tomato is due to a virus which also infects plants of the cucumber family as well as spinach, celery, pepper, and a wide variety of weeds and flowers. Common mosaic. Mottled areas of light and dark green in the leaves are the most characteristic symptom of this disease. The dark green areas usually appear somewhat raised and puckered (Fig. 2). The young leaves at the tips of the growing branches tend to be bunched and to unfold unevenly. Plants affected in the early stage of growth are usually stunted and have a yellowish cast. Ordinarily the fruit does not show any marked disfiguration. Both number and size of fruit are reduced, however, resulting in lowered yields. If infections occur before or during transplanting to the field, the yield may be reduced by as much as 50 percent. The common-mosaic virus is so extremely infectious that a person can transmit it merely by touching a healthy tomato plant after having touched an affected plant. Transplanting, cultivating, weeding, Circular No. 912 Leaves of plants affected with common mosaic show light and dark green mottling. Dark areas are usually raised and puck- ered. (Fig- 2) Yellow mottling of the leaves is characteristic of aucuba mosaic. Mottling of the fruit may often ac- company these symptoms on the leaves. (Fig. 3) Q o o Tomato D/seases 9 and attacks by insects (see aphids, page 43) are possible ways of spreading the virus. Greenhouse infections may often be correlated with hand operations such as pruning and tying the plant. Since the virus will live for many years in dried leaves and stems, it may be spread to growing plants from the remains of the previous crop. This method of transmission does not appear to be important in field-grown tomatoes but may be responsible for some infections in greenhouse crops, especially where one crop is followed almost im- mediately by another. Certain ornamental plants and perennial weeds such as zinnia, snapdragon, phlox, petunia, ground cherry, and horsenettle are some- times infected by the virus and may serve as sources of early infec- tions in the greenhouse, seedbed, and field. Often mosaic infections in tomatoes originate from the use of to- bacco in one form or another by the grower or his helpers. As already mentioned, the virus causing tomato mosaic is a strain of the common tobacco-mosaic virus; it affects tobacco in much the same way that it affects tomatoes. It is not killed in most tobacco-manufacturing pro- cesses and hence is present in a virulent form in most kinds and brands of chewing and smoking tobacco. The common-mosaic virus is rarely seed-borne except in freshly extracted seed. For that reason seed-transmission of the virus is probably of little importance in tomato production. Aucuba mosaic. This disease causes a striking yellow mottling of the leaves (Fig. 3) and sometimes yellowing and even bleaching of the upper parts of the stems and branches. The fruit may be mottled — light and dark green when immature, and yellow and red when ripe ■ — and generally unacceptable for marketing. The aucuba-mosaic virus is introduced and spread among tomato plants in much the same way as the common-mosaic virus, except that the aucuba virus is not quite so easily transmitted by contact and, so far as is known, is not spread by insects. Cucumber mosaic. Tomato plants affected with this disease in the early stages of growth are yellowed, bushy, and considerably stunted. Although the leaves may show a mottling suggestive of common mosaic, the most pronounced symptom is the "shoe-string" appearance of the leaves. Sometimes the leaves are so distorted that very little remains of the leaf blade except the midrib (Fig. 4). Severely affected plants produce but few fruit, and these are usually smaller than fruit from healthy plants. The number of cultivated and wild plants susceptible to the cu- cumber-mosaic virus is larger than the number susceptible to the common- and aucuba-mosaic viruses put together. The virus over- winters in the roots of certain perennial weeds such as pokeweed, catnip, and milkweed. At least five species of aphids, as well as the 10 Circular No. 912 These three leaves show types of abnormal growth caused by the cucum- ber-mosaic virus. Often there is little left except the midrib. (Fig. 4) 3 striped and spotted cucumber beetles, are capable of transmitting the virus from the overwintering weed hosts to the tomato. The cucumber-mosaic virus is not transmitted in tomato seed, is not easily transmitted to tomatoes by rubbing or handling the plants, and does not persist in the soil or on the hands of workers. Control of mosaic diseases. Eradicate all perennial weeds from the seedbed, garden, field, greenhouse, and the area around the green- house. If you have been working with plants of any kind, or have been using tobacco in any form, wash your hands in a solution of trisodium phosphate (1 teaspoonful dissolved in 1 quart water) or in milk to inactivate any viruses before handling tomato seedlings or transplants. Undiluted skim or whole milk or 4 ounces powdered milk dissolved in 1 quart of water may be used. Insist that all your helpers do like- wise. If you are operating a greenhouse, you might display prominent signs over the entrances to the tomato houses, saying, "Visitors are asked not to touch the plants." Just before handling tomato plants at transplanting time, spray them with whole or skim milk or a mixture of 1 pound of powdered milk and 1 gallon water. Apply 1 gallon of the milk to every 20 square yards of plant bed. Dip hands in milk every few minutes to keep them moist whenever handling plants. Do not grow tomatoes in the garden or field next to crops such as pepper, potato, cucumber, tobacco, and related plants which are likely to carry viruses capable of infecting tomatoes. If possible, tomato Tomato Diseases 11 plants should not be grown in seedbeds or sections of greenhouses used for flower production. Do not plant vine crops such as cucumbers and melons next to greenhouses in which a fall or spring crop of tomatoes is to be grown ; otherwise, virus-bearing aphids and cucumber beetles may move into the greenhouse as the cucumbers and melons mature. Fumigate, spray, or dust greenhouses at frequent intervals to con- trol aphids (page 43). This measure is particularly worthwhile if begun in the fall before freezing weather has caused insects to move into the greenhouse from out-of-doors. Aphid control is also important in preventing the spread of mosaic diseases after they have become established on a few plants in the greenhouse. Streak Diseases Two kinds of streak diseases are found in Illinois: single-virus streak, which occurs mostly in greenhouse tomato crops, and double- virus streak, which affects both greenhouse and field plantings. Single-virus streak, as the name indicates, is caused by a single virus, which is closely related to the virus causing common mosaic. However, the only symptom the two diseases have in common is a more or less distinct mottling of the leaves. Under conditions not well understood, tomato plants infected with this streak virus develop brown streaks on the stems and petioles (leaf stalks) . Small, irregular, dark brown spots appear on the leaves. The pith or central stein tissue shows a brownish discoloration. During the early stages of double- virus streak, leaves of a diseased plant may wither and die. Later the fruit is also affected, show- ing small, greasy, brown areas of ir- regular shape. (Fig. 5) 12 Circular No. 912 Fruit is often marked with slightly sunken, brown rings about V? inch in diameter. They may not, however, display any symptoms. Double-virus streak is the result of a double infection with (1) the common-mosaic virus and (2) the so-called latent potato virus. This latent virus occurs in plants of many potato varieties grown in this country, but doesn't produce marked symptoms on potatoes. When it occurs alone in the tomato plant, it causes only a very mild mottling of the leaves. However, when a tomato plant already infected with the common-mosaic virus becomes infected with the latent virus, then double-virus streak develops. Serious damage may follow. Like common mosaic and single-virus streak, this disease is char- acterized by mottling of the leaves. Small, grayish-brown dead spots develop on the leaves along with the mottling. The leaves may wither and die in the early stage of the disease (Fig. 5). The pith is not dis- colored as it is in plants affected with single-virus streak, but many narrow, dark brown streaks appear on the stems and leaf petioles. Fruit is marked with small, irregular, greasy, brown patches % to % inch in diameter. Control of streak diseases. Since the common-mosaic virus helps to cause double-virus streak, the same general precautions that are given for control of mosaic diseases should be followed. It is particu- larly important not to plant tomatoes next to potatoes in the garden or field. After handling potato tubers or vines be sure to wash your hands with soap and water or a trisodium phosphate solution before working around or handling tomato plants. Do not permit the use of tobacco around the tomato plants. Affected plants should be promptly removed from the greenhouse. This measure, however, may be of little value if the disease is well distributed throughout the planting. **P- ' One characteristic of bacterial wilt is the water-soaked, brownish streak that can be observed in the central part of the stem when the stem is split lengthwise. (Fig. 6) Tomato Diseases 13 Bacterial Wilt This disease, caused by Psendomonas solanacearum, can be found occasionally in Illinois fields set with southern-grown plants. Losses from this trouble are slight for the state as a whole. Affected plants wilt rather rapidly and soon die. There is no spot- ting or yellowing of the leaves. If the stem is cut lengthwise near the ground level, a water-soaked or brownish discoloration of the pith or central tissue can be observed (Fig. 6). A slimy ooze appears if the cut stem is squeezed. This distinguishes the disease from Fusarium and Verticillium. Cavities form in the pith in the later stages. Control. The causal bacteria are spread from diseased to healthy plants and from field to field by drainage water following rains. For this reason infected plants, if relatively few, should be removed from the field at once. Do not replace them with healthy plants, for they also are likely to become infected. If a field shows a relatively high percentage of infection, do not grow tomatoes there for four or five years. Instead, use it for crops that are not susceptible, such as small grains, legumes, and corn. Under no circumstances rotate tomatoes with potatoes, peppers, or eggplants. Leaf Roll A non-infectious disease, leaf roll is widespread in Illinois in some years. It generally follows extended periods of wet or dry weather and is most likely to occur on plants in poorly drained soils. It has also been observed after close cultivation and extremely close pruning, and is worse on staked tomatoes. The rolling generally starts on the lower leaves and proceeds As the name "leaf roll" suggests, this disease is character- ized by rolling of the leaves. Lower leaves are usually affected first. Close cultiva- tion and pruning may bring on this disease. (Fig. 7) 14 Circular No. 912 upward until, in some instances, almost all the leaves are affected (Fig. 7). In severe cases the rolled leaves are somewhat thickened and tend to rattle when the plant is shaken. Ordinarily, affected plants bear a normal or near-normal crop of fruit. But sometimes the plants may lose one-third of their leaves, with a corresponding loss in fruit quality, because rains and winds whip and riddle the rolled leaves. Control. To lessen damage from leaf roll, choose well-drained areas for tomatoes, particularly if you are growing them in a garden. Do not cultivate deeply near the plants. Where leaf roll is an annual problem, it may be necessary to stop priming and staking tomatoes. Maintain as uniform a supply of soil moisture as possible. Tomatoes require as least 1 inch of water per week, supplied as rainfall or irri- gation. Watering with a soaker hose is preferable in the home garden. Mulching tomatoes with straw, corn cobs, grass clippings, or wood shavings, but not diseased plant refuse, will help to maintain a uniform soil moisture. The following varieties are resistant or intermediate in resistance to leaf roll: Alpha 417, Bradley, Burpee Hybrid, Glamour, Golden Boy, Manapal, Moreton Hybrid, Pa 103, Sioux, Sunray, and Valiant. Bacterial Canker At one time bacterial canker was one of the most destructive to- mato diseases in greenhouse and field plantings in Illinois. In recent years losses from this disease have been slight, principally because of the in- creased use of certified and treated tomato seed by south- ern plant growers. However, growers who save their own seed and ignore control mea- sures can expect to suffer losses from canker if weather condi- tions favor its development. The disease is caused by a bacterium, Corynebacterium michiganense, which, so far as One or two stalks of a plant may die as a result of infection with bacterial canker, while the rest of the plant still seems to be free of the disease. (Fig. 8) c Tomato Diseases 15 Discolorations typical of bacterial canker (bottom), Verticillium wilt (middle), and Fusarium wilt (top) are shown by these stems that have been slit lengthwise to reveal these abnormalities. Bacterial canker causes lines of creamy white, yellow, or yellowish brown near the edges. The dis- coloration is usually lighter than in the other two diseases. (Fig. 9) is known, attacks only the tomato. First symptoms are usually droop- ing of the upper leaves and curling of the leaflets. Soon wilting be- comes pronounced, progressing from the bottom of the plant upward. Later, the leaves wilt and die, but the petioles usually remain green and firm. They are very hard to remove from the main stem, thus differing from the petioles of plants affected by Fusarium and Ver- ticillium wilts. This characteristic aids materially in field diagnosis of bacterial canker. Individual stalks may be killed early with the rest of the plant appearing healthy for some time (Fig. 8). 16 Circular No. 912 Yellowish to yellow-brown streaks usually appear on the stems of infected plants. Streaks in the stem may crack open forming a canker. If an infected stem is cut lengthwise, creamy white, yellow, or yellow- ish brown lines can be seen close to the edge on one or both sides (Fig. 9). These are caused by the bacteria in the water-conducting tubes and their subsequent spread to adjacent tissues. The discoloration is generally much lighter than that typical of Fusarium or Verticillium. Two distinct types of fruit infections result from this disease: (1) internal infection and (2) external infection, or fruit spot. Internal infection, which occurs through the vascular (food- and water-conduct- ing) channels of the plant, is by far the more important. The dis- colored tissue typical of the disease may often be traced directly through an infected plant into its fruit and seeds. This type of fruit infection does not materially affect the marketability of the fruit, but it is largely responsible for outbreaks of the disease the following year. Fruit spot, or bird's-eye spot, as it is often called, is a very common form of bacterial canker under Illinois weather conditions. The spots appear as tiny light dots which soon show a rough brownish center Fruit spot (bird's-eye spot) first appears as tiny light dots. These soon enlarge, with rough brownish spots appearing in the center. (Fig. 10) Tomato Diseases 17 surrounded by a white halo (Fig. 10). Fruit may have only a few spots or they may be literally covered with them. The most serious aspect of this infection is its effect upon the market value of the fruit. The causal bacteria are transmitted on and in the seed and on seedlings from diseased seed or infested soil. Wind, rain, and cultural practices account for local spread once the bacteria are established in plants or soil. Exactly how long the organism will live in the soil has not yet been determined but it has been proved to survive in New York for only one year after an infected crop. Control. Bacterial canker furnishes an outstanding example of the importance of using clean, disease-free seed. Never save seed from fields known to have bacterial canker. If you buy seed, it will be well worthwhile to get only certified seed since such seed is usually canker- free. If you use non-certified seed of unknown origin, give it an eradi- cative seed treatment (page 48). Disinfest the seedbed soil (page 49) if it is not known to be free from the disease, or else replace it with soil that has not grown tomatoes. If soil is known to be infested with canker, the best thing to do is to grow other crops for at least three years before planting tomatoes again. In small gardens where three-year rotations are not practical, pulling up and destroying tomato vines after the crop is harvested will help to control bacterial canker. Fusarium Wilt Fusarium wilt is still one of the most prevalent field and green- house diseases of tomatoes in Illinois despite the fact that numerous Pronounced yellowing of individual leaves is char- acteristic of the begin- ning stages of Fusarium wilt. A single leaf may turn yellow first, with the discoloration spread- ing over the entire plant. After a leaf turns yel- low, a slight touch will make it drop from the stem. (Fig. 11) 18 Circular No. 972 desirable resistant varieties have been available for some time. These varieties have made it possible to continue growing tomatoes on several thousand acres of wilt-infested soil in Illinois. Without them, Fusarium wilt would undoubtedly be the most damaging tomato disease in this state. It is present in all important tomato-growing regions of the United States, but does its greatest damage in the southern states and in northern states during excessively hot seasons. The disease is caused by a soil fungus (Fusarium oxysporum f. lycopersici) which enters the roots, and, like the bacterial canker organism, does its damage by growing in the food and water channels of the plant. It is believed that a toxic substance secreted by the fungus causes the wilting and death of the plant. Many growers know this wilt disease as "yellows" because of the characteristic yellow color of infected plants (Fig. 11). The first symp- tom of the disease is the yellowing of a single leaf or a slight wilting and drooping of the lower leaves. If a section of the stem close to the base of the plant is examined now or later, a distinct brown discolor- ation of the water- and food-conducting channels may be seen (Fig. 9). As the disease becomes more acute, wilting and yellowing become progressively worse until finally the entire plant wilts and dies. In damp weather the pinkish-white growth of the causal fungus may be seen in wounds or on leaf scars of plants killed or severely infected by the wilt organism. A black-rot condition in the small side roots is typical of this disease. Shortly after a petiole and the leaflets on it become infected and yellowed, they will drop from the main stem with a mere touch. Petioles of plants infected by bacterial canker (page 14) seldom turn yellow and are very difficult to remove from the main stem. This fact aids materially in telling these diseases apart under field conditions. The first symptoms of Fusarium wilt generally appear about the time of bloom or shortly after the set of the crown-cluster fruit, al- though the infection may occur any time during the life of the growing plant. The disease is favored by hot weather, and the high summer temperatures common in Illinois cause infections to progress very rapidly. Growth and reproduction of wilt are most active when the soil temperature is between 82° and 84° F. Plants sometimes die within 2 to 4 weeks after the first symptoms appear. Fusarium wilt is introduced into a new area in or on the seed, by seedlings grown in infested soil, by dust and rain storms, and on farm implements. Seed is often considered responsible for introducing the disease into widely separated areas, while the other methods account largely for local spread. Seedbed infections commonly result in severe losses. Seedlings grown on infested soil usually do not show the disease until after they have been transplanted for some time. Thus it is ( Tomato Diseases I 9 important that the seedbed soil be disinfested unless it is known to be disease-free. Once the wilt fungus becomes established in the soil, it generally persists there for years, making any reasonable rotation worthless. Control. The usual control of Fusarium wilt is to grow immune, resistant, or highly tolerant varieties, many of which are now avail- able. Immune varieties are seldom affected by wilt. Resistant or tol- erant varieties are not affected when soil temperature is below 70° F. Wilt-resistant or immune, red-fruited varieties suitable for grow- ing out-of-doors in Illinois are Campbell KC-146, Floradel, Floralou. Harvester, Heinz 1350 and 1370, Homestead, Indian River, Manalucie, Manapal, Manasota, Superman, Supermarket, Supreme, Surprise, and Roma (paste). Greenhouse varieties are (red) Michigan-Ohio Hybrid, Ohio WR Red Jubilee, Ohio WR Globe, Tuckcross O; (pink) Hoosier Hybrid, Ohio WR 3, 7, 25 and 29. Yellow-fruited varieties are WR Jubilee and Sunray. Check your seed catalog for a complete descrip- tion of varietal characteristics. If the wilt fungus is known to be present in greenhouse soils, re- sistant varieties should be used and the soil should be disinfested (page 49) . Tomatoes should not be grown on the same ground oftener than once in three or four years since a light infestation of wilt can be greatly increased by too-frequent cropping with tomatoes. It is ad- visable also to pull up and destroy wilt-affected tomato plants in small plantings at the end of the season. Certified seed is less likely to carry the wilt fungus than uncerti- fied seed. If you use home-saved seed, be sure that the fruit for this seed comes only from plants completely free from wilt. Verticillium Wilt The symptoms of this disease are almost identical to those of Fu- sarium wilt (Figs. 9 and 11) and the two ordinarily cannot be distin- guished except by laboratory examinations. Verticillium wilt is caused by a soil fungus (Verticillium albo-atrum) which also attacks pepper, bramble, strawberry, eggplant, potato, and a wide variety of other plants. The causal fungus may be carried at times on or in the seed, which may account for its introduction into widely separated areas. Verticillium wilt, unlike Fusarium wilt, thrives best under cool moist conditions and therefore is more serious in the northern states and Canada than in the southern states. Control. Heinz 1350, Harvester, Roma V F, and Superman are re- sistant to certain strains of the Verticillium wilt fungus. Otherwise, control measures are the same as those described for Fusarium wilt. If 20 Circular No. 912 the disease becomes established in the seedbed or greenhouse, the soil must be disinfested if tomatoes are to be grown profitably. Do not plant tomatoes in fields where eggplant, pepper, and okra have been grown, especially if these were affected by wilt. Gray Leaf Spot Gray leaf spot, caused by the fungus Stemphylium solani,1 is a comparatively new disease of tomatoes in Illinois. Although it may have been present in slight amounts before 1949, it did not occur in ( The brownish-black spots characteristic of gray leaf spot may grow to 3/16 inch in diameter. As they grow, they become shiny and glazed. Later they dry out, often splitting as they do so. (Fig. 12) epidemic proportions until then. That year it caused severe defolia- tion in several fields in Vermilion county. This disease is potentially more destructive than either early blight (page 21) or Septoria leaf spot (page 23), because severe infections occur earlier in the season and the fungus spreads more rapidly from lower to upper leaves. Warm, wet weather hastens the spread of the fungus and its subse- quent penetration of the leaves. Gray leaf spot is limited to the foliage and stems; no lesions de- velop on the fruit. Small, brownish-black spots, either irregular or circular in outline, are the first symptoms on the leaves (Fig. 12). The spots grow larger, 3/16 inch usually being the maximum diameter. Often 1 Another species of Stemphylium occurs on tomatoes in Florida. ( Tomaio Diseases 21 they cover most of the total leaf surface, the tip quarter being espe- cially spotted and browned. Lesions on the petioles and upper parts of the stems are elongated and brown. The spots on the leaves become shiny and glazed as they enlarge, somewhat resembling those of bacterial spot (page 25). After the spots start to dry out, they often crack from side to side. The central part may break out entirely, giving a shot-hole appearance to the leaf. Usually the leaf is quite yellowed at this time. Soon the entire leaf wilts, dies, and falls off the stem. The gray leaf spot fungus apparently can overwinter easily on tomato-plant refuse. It has been reported in Florida on eggplant and pepper and on three species of weeds belonging to the tomato family. Several other weeds related to tomato were inoculated artificially and found to be susceptible. Gray leaf spot infections have been seen on horsenettle (Solarium carolinense) growing in Illinois tomato fields affected by the disease. Control. Eradicative seed treatment (page 48), soil disinfestation (page 49), three- or four-year rotations, and spraying or dusting with fungicides (page 50) in the seedbed and field are recommended as preventive measures against gray leaf spot. Zineb, maneb and Dithane M-45 are effective if applications are made before the disease appears and if leaves and stems are well covered. Resistant varieties are Flora- lou, Floradel, Indian River, Manalee, Manalucie, Manapal, and Ohio WR Red Jubilee. Early Blight Early blight, caused by a fungus (Alternaria solani) , may occur as a collar rot, a stem canker, a leaf spot, or a fruit spot. Collar rot is characterized by large, brown, slightly sunken, irregular lesions on the stems of seedlings and trans- plants at or slightly above the ground level (Fig. 13). Similar but smaller stem cankers may develop for a con- siderable distance above the ground level. Such plants are apt to die or be unproductive if set in the field. Seedlings and transplants affected with collar rot show large, brown lesions at the level of the ground or slightly above it. Other early-blight lesions (stem cankers) may appear farther up on the stem. (Fig. 13) 22 Circular No. 912 The leaf-spot stage can be distinguished by irregular, brown spots which are often marked with concentric rings or ridges giving a "target-board" effect to the spots (Fig. 14). Occasional spots may be almost V2 inch in diameter. Abundant rainfall and high temperatures may result in severe leaf infections and loss of much of the foliage. Often so many leaves are lost that there is considerable sunscalding of the fruit. The result is usually off-quality conditions in the fruit, such as flabbiness, cracking, orange instead of red color, and off-flavors. The susceptibility of the fruit to anthracnose is increased. Lesions may also occur on the flower stems and cause the blossoms to drop. ( Early -blight infec- tions on leaves often look like tar- get boards because of the concentric brown rings. Leaves affected in this way commonly drop from the plant. (Fig. 14) Fruit spots caused by early blight are dark, sunken, and leathery, occurring at the stem end. The fungus often completely covers these affected areas, appearing as a brown moldy growth marked with con- centric rings like those on the leaves. The fruit may drop prematurely. Control. Eradicative seed treatments (page 48) and seedbed disin- festation (page 49) should be used to prevent seedling infections. Provide ample ventilation and avoid overwatering and overcrowding of the seedlings. Discard any transplants with cankers on the stem. Plants should not be held in the seedbed for any length of time after they have reached the proper stage for transplanting. Nor should southern-grown plants be held in storage any longer than absolutely necessary after they are received. General sanitation in the garden and field will help to prevent infection. Ground cherry, horsenettle, night shade, and other weeds related to the tomato should be eradicated from tomato plantings. In commercial fields it helps to cut up vines with a disk and plow them under deeply in fall or early spring. ) Tomato Diseases 23 Spraying or dusting plants in the field with maneb, zineb, Dithane M-45, Polyram, Daconil 2787, ziram, or captan fungicides (page 50) will help to control early blight if this practice is started before the disease appears. Septoria Leaf Spot Septoria leaf spot is most severe during rainy seasons and in fields where plants are crowded and bearing a heavy fruit load. It is caused by the fungus Septoria lycopersici. Although the disease is most serious under field conditions, damage may occur in the seedbed. The lower leaves of seedlings may become severely spotted if held too long before transplanting to the field. As a general rule, the disease is slow in getting started and is not much in evidence before the first or middle of July, or not until the plants have begun to set fruit. Small gray spots, with tinv black specks in the center and with black or brown borders, are the first evidence of the disease. They may remain small or may grow to about % inch in diameter (Fig. 15) . The lower leaves are attacked first. Frequent showers and air temperatures of from 60° to 80° F. bring about favorable conditions for the spread and development of the fungus. Under these conditions, infections spread rapidly with a pro- gressive loss of foliage until only a few leaves are left at the tip of the stem or branch. The fungus may also attack the stems, leaf petioles, * * * * f| ^p" First symptoms of Septoria leaf spot are small gray spots with black dots in the center and with black or brown edges. These spots may become as large as Vs inch in diameter. (Fig. 15) 24 Circular No. 912 blossoms, and fruit stems. Fruit spotting is seldom of any importance, but, as with early blight, fruit on plants defoliated by Septoria leaf spot are apt to be of poor quality and very susceptible to anthracnose. Summer infections of Septoria leaf spot originate from infected seed, from the remains of old plants left in the field from the previous year, or from infected weeds such as horsenettle, ground cherry, night- shade, and Jimson weed. The fungus is spread by splashing rains and by the hands and clothing of those working with wet plants. Control. The control measures given for early blight (page 21) apply in general to the control of Septoria leaf spot. These measures are eradicative seed treatments, seedbed disinfestation, proper cultural practices, general sanitation, weed control, and spraying or dusting with fungicides. In general, this disease is more difficult to control with fungicides than is early blight. Good control is almost impossible if fungicides are not applied until after the disease appears. Maneb, Dithane M-45, Polyram, Daconil 2787 and zineb (page 50) are some- what more effective against this disease than other kinds of fungicides. ( 3 Lesions caused by bacterial spot are first raised; later they sink and have a scab-like appearance. In Illinois these spots are the most serious part of this disease. (Fig. 16) Tomato Diseases 25 Bacteria! Spot Bacterial spot is widely distributed in Illinois. It is particularly serious in warm seasons with frequent or heavy dews. The disease is common as a leaf and fruit spot on pepper as well as on the tomato. Leaf spots appear as small, water-soaked areas which later turn brownish-black. The spots are somewhat irregular in outline and have a greasy appearance on the upper surface. Several lesions may cause a leaflet to turn yellow. Lesions may also occur on the flower stems and cause the blossoms to drop. Spots on the fruit first appear as small, black, raised "pimples" which are surrounded by water-soaked areas. Later the raised portion sinks, forming a cavity and typical scab lesions (Fig. 16). The development of these spots on the fruit and flower stems is the most serious aspect of the disease in Illinois. The bacterium causing the disease is Xanthomonas vesicatoria. Bacteria overwinter on the seed and probably on occasion in the soil. Control. Eradicative seed treatments (page 481 will rid the seed of any spot bacteria. Seedbed disinfestation (page 49) may also be of some help. Spray seedlings in the plant bed every 5 days with a mix- ture (Agrimycin 500) of fixed copper and streptomycin in water. ]\Iix at the rate of 5 pounds in 100 gallons of water and apply at 2aX> to 3V2 gallons per 1,000 square feet of plant bed. This spray provides a con- centration of 4 pounds of fixed copper (53 percent copper as metallic) and 100 parts per million of streptomycin. A mixture also may be made by combining at this rate a fixed copper fungicide (page 50) with any of several streptomycin formulations. Streptomycin is sold for use on plants under such trade names as Agri-strep, Phytomycin, Agri- mycin 17 or 100, Stauffer Streptomycin, Streptomycin Antibiotic Spray Powder, and Ortho Streptomycin. Do not apply streptomycin after plants are set in the field. Spray in the field at 7- to 10-day intervals with a fixed copper fungicide alone (page 50) or mixed with maneb, zineb, Dithane M-45, Polyram, or Daconil 2787. Leaf Mold Leaf mold, caused by the fungus Cladosporium julvum, is princi- pally a greenhouse trouble although on occasion it may develop in the garden or field. All above-ground parts of the plant may be affected, but generally the greatest damage occurs to the leaves. The fruit itself is rarely attacked. Yellowish or light green spots on the upper side of infected leaves are the first evidence of the disease. The lower surfaces of these patches are often covered with a grayish-purple moldy growth (Fig. 17) composed largely of spores of the fungus. When humidity is high, the fungus develops rapidly on the foliage. It is spread as spores from plant to plant by watering and air currents, 26 Circular No. 912 The undersides of leaves affected with leaf mold often show patches of a grayish-purple moldy growth. On the upper sides, yellowish or light green spots correspond to the moldy patches. (Fig- 17) ( and through contact of the leaves. Infections usually progress from the lower leaves upward. If control measures are not practiced, the entire plant may be affected, and the crop greatly reduced. Control. Adequate ventilation and temperatures of at least 60° to 65° F. throughout the growing season will lessen damage in the green- house. At night keep the temperature of the greenhouse higher than that outdoors. This will reduce the amount of moisture that forms on the leaves and thus help to control the disease, since moisture is essential for the growth of the mold fungus. If leaf mold becomes serious, some night heating may be needed as late as the middle of June and as early in the fall as the first of September. The control obtained in this way will more than pay for the additional heating. If at all possible, avoid syringing the plants with water. Mold-resistant, red-fruited varieties for greenhouse production are: (standard varieties) Improved Bay State, Vantage, Vinequeen, Waltham Mold-Proof Forcing; (hybrids) Michiana, Tuckcross W, and Veegan. Harris' Pink Trophy is a resistant pink variety but it's per- formance under Illinois conditions is unknown. Tomafo Diseases 27 Late blight first ap- pears as dark brown water-soaked areas on leaves and stems. Often a pale green band surrounds the brown spot on the leaf. (Fig. 18) Spraying or dusting with maneb, Dithane M-45, zineb, or fixed- copper fungicides (page 50) will help to prevent leaf-mold infections in the field but may be of little value in the greenhouse. Late Blight The fungus (Phytophthora infestans) that causes the late-blight disease of potatoes is also responsible for late blight in tomatoes. When conditions are extremely favorable for infection (temperatures between 50° and 70° F., plus high humidity or rainfall) and where protective fungicides have not been applied, the disease may spread throughout a large tomato field in a few days' time, killing the vines and rotting all green and ripe fruit. First symptoms of late blight are irregularly shaped, dark brown, water-soaked areas on the stems and leaves (Fig. 18) . A pale green band of tissue usually surrounds the affected area on the leaf. The grayish, moldy growth of the fungus may be found on the underside of these spots. Severely affected plants look as if they have been killed by frost. Fruit rotting usually starts at or near the stem end and soon spreads over the entire fruit (Fig. 19). Rotted areas are greenish-black with a rather firm but slightly wrinkled surface. Under moist conditions the growth of the fungus may be apparent on the surface of affected fruit. Infections on tomatoes originate for the most part from imported tomato plants, from nearby potato fields, or from infected greenhouse tomatoes. After infection begins, it is spread by the microscopic spores or seeds of the fungus. These are produced by the hundreds on each individual spot and may be carried for some distance by air currents. Since a new crop of spores is produced every two or three days under 28 Circular No. 912 ( Late blight attacks both green and ripe fruit. Rotted areas are greenish- black and somewhat wrinkled, though firm. (Fig. 19) favorable conditions, a single blighted tomato or potato plant may give rise to a tremendous number of infections in a field. Control. Maneb, Dithane M-45, Polyram, zineb, or fixed-copper fungicides (page 50) will control late blight satisfactorily, particularly if they are applied before the disease appears. Tomatoes should not be planted in the field following potatoes, nor should these crops be planted in adjacent fields. Buckeye Rot Buckeye rot, caused by a fungus {Phytophthora parasitica), occurs on either green or ripe fruit and is most common in poorly drained fields during warm, wet weather. The rot appears as a greenish to brownish water-soaked spot near the blossom end of the fruit where it is in contact with the soil. The rotted area enlarges rapidly in warm weather until one-half or more of the fruit is covered. When the rot develops slowly, definite zona- tions or dark concentric rings appear in the decayed area (Fig. 20). In wet weather the grayish-white fungus growth may develop on the rotted fruit. These tomatoes in- dicate how "buck- eye rot" gets its name. Infection starts as a greenish to brownish spot near the blossom end and enlarges rapidly in warm weather. (Fig. 20) Tomafo Diseases 29 %J"% 4*h$2!Fl Control. Good drainage is particularly important in preventing losses. A three-year rotation with crops other than eggplants or peppers will also help to control the disease. Staking plants in the garden will help considerably by keeping the fruit from touching the soil. Spraying or dusting with maneb, Dithane M-45, Polyram, zineb, or a fixed-copper fungicide (page 50) will help to protect the fruit against infection. Blossom-End Rot Blossom-end rot is a noninfectious disease caused by a deficiency of calcium. It is usually more severe on staked tomato plants than on those that are not and is worse in some seasons than in others. Condi- tions that favor blossom-end rot also favor leaf roll (page 13). Although the disease may appear at any stage of fruit growth, the fruit seems most susceptible when it is one-half to two-thirds mature. A small water-soaked spot around or near the blossom end is the first symptom of the disease. Later the spot enlarges, soon becoming sunken, brown, and leathery (Fig. 21). In severe cases it may involve more than half the affected fruit. It is very common for secondary fungi and bacteria to attack fruit affected with blossom-end rot and thus cause further rotting. Control. In the greenhouse and garden, the disease can be pre- vented to some extent by maintaining a uniform supply of soil moisture and by avoiding the use of excessive amounts of ammonia or nitrated nitrogen and highly soluble potassium salts. A light application of dolomitic limestone, gypsum, superphosphate, or hydrated lime should be worked into the soil to a depth of 4 to 6 inches before planting. The Florida Experiment Station suggests that a calcium chloride solution 30 Circular No. 912 ( Blossom-end rot is just starting on the top tomato. As the rot spreads it becomes sunken and leathery, as on the bottom tomato. (Fig. 21) Tomato Diseases 31 (4 pounds of 95-percent material or 5 pounds of 78-percent dissolved in 100 gallons of water) be sprayed on the leaves when blossom-end rot is first noted or when it is anticipated. Such sprays should be used during periods of most rapid growth. In Illinois commercial and home gardens, gardeners might try calcium chloride sprays on an experi- mental basis, beginning when the first fruit are the size of golf balls and continuing at weekly intervals until 3 or 4 applications have been made. Prolonged, periodic applications of this chemical may cause marginal leaf burn. Botrytis Fruit Rot Severe losses occur in greenhouse crops some years as a result of Botrytis fruit rot (caused by the fungus Botrytis sp.) . Damp, cloudy weather appears to be very favorable for outbreaks of the disease. Syringing the plant with water and jarring the plant to insure pollina- tion loosen tremendous numbers of the fungus spores (seeds) into the air. These spores are then carried by air currents to other plants. The disease first appears as a small, water-soaked spot near the stem end of the green fruit. The infection spreads rapidly, and ulti- mately most, if not all, of the fruit may be affected (Fig. 22). The A grayish, powdery, moldy growth covers diseased areas of tomatoes af- fected with Botrytis fruit rot. (Fig. 22) 32 Circular No. 912 diseased area is covered with a grayish, powdery, moldy growth com- posed of countless fungus spores. Although infection is most evident on the fruit, the main stem, the flowers, and the fruit stalks may also be affected at times. Control. Measures for the control of this disease are essentially the same as those for leaf mold (page 26). It is particularly important not to syringe plants. Carefully picking diseased fruit and removing them from the greenhouse may help to keep losses at a minimum, particularly if this is done when the disease first appears. Spraying or dusting with maneb, Dithane M-45, Polyram, zineb, or fixed-copper compounds (page 50) may help prevent infection, but cannot be relied upon exclusively. Anthracnose Anthracnose, or ripe rot, caused by the fungus C olletotrichum phomoides, is the most widespread and destructive tomato fruit rot in Illinois. It appears to be most common on plants growing in poorly drained and infertile soils, and on plants which have lost much of their foliage from disease or other causes. The causal fungus can overwinter in soil debris and, as recent experiments at the New York (Geneva) Station have shown, it can spread from infected leaves to nearby fruit. Although many infections probably take place when the fruit is still green, the disease is not evident until the fruit is ripe or nearly ripe. Then it appears as small, slightly sunken, circular, water-soaked spots (Fig. 23), which enlarge rapidly in warm weather. The center Anthracnose becomes evident when fruit is ripe or nearly ripe, making its appearance as small, round, slightly sunken, water-soaked spots. (Fig. 23) Tomato Diseases 33 of each spot becomes darkened and in moist weather may turn pink. These rotted areas are commonly marked with concentric rings. The whole fruit may be almost completely covered with anthracnose spots approximately 24 hours after picking if conditions are favorable. Control. Some of the losses from anthracnose can be avoided if adequate soil fertility is maintained and if the soil is well-drained. A four- or five-year rotation will also help control the disease. In the home garden, anthracnose can be largely controlled by staking the plants to keep the fruit away from the soil and by har- vesting all ripe fruit at each picking. Decaying fruit left under the plants serve as sources of infection for the remaining fruit. Maneb, Dithane M-45, Polyram, Daconil 2787, zineb, ziram, and captan fungicides (page 50) are valuable as protectants against anthracnose infections. They are effective only if application is started when the first fruit is no larger than a golf ball or not later than two weeks after the first flowers are seen. Commercial growers should apply maneb or Dithane M-45 (4 pounds to 100 gallons of water) to the soil under the plants at lay-by time. This practice prevents infection of the fruit from the fungus on the soil. Minor Fruit Rots Several minor rots may damage the tomato fruit in the field or, in the case of "green wraps," during shipment to market. Many different species of fungi and bacteria are responsible for such rots. They com- monly infect the fruits through insect-feeding punctures, growth cracks, or mechanical injuries. Some of these organisms cause a distinct odor of fermentation. One of the most common types is a soft, watery rot which makes the diseased fruit resemble hanging bags of water. These fruit rots appear to be least severe on plants growing in well-drained soil. They are generally most prevalent during and after periods of excessive rainfall. Control. Grow tomatoes in well-drained soil. Use care to avoid injuring fruits that are picked and wrapped for shipment while they are still green. Spraying or dusting with maneb or zineb fungicides may aid in controlling some of these rots, particularly if an insecticide also is applied. Injury from 2,4-D1 The weed-killing chemical 2,4-D has caused serious damage in Illinois to tomato and other susceptible kinds of plants, such as grapes 1 The herbicide commonly known as 2,4-D is 2,4-dichlorophenoxyacetic acid. The herbicides 2,4,5-T and MCPA may also severely injure crop plants and cause symptoms similar to those of 2,4-D injury. The herbicide 2,4,5-T is 2,4,5- trichlorophenoxyacetic acid and MCPA is 2-methyl-4-chlorophenoxyacetic acid. This discussion applies equally to injury from any of these herbicides. 34 Circular No. 912 (wild and cultivated), melons, sweet potatoes, beans, roses, dogwood, and redbud trees. Weedkillers such as 2,4-D are quickly absorbed by the leaves and transported throughout the plant. Only a trace of the chemical is needed to kill susceptible plants. Unfortunately, 2,4-D is unable to differentiate between broadleaf weeds and crop plants. The active ingredient may be carried by air currents and cause injury at a distance of % mile or more from the sprayed area. Dust formula- tions may be carried for several miles. Contaminated sprayers and pesticide containers may also be responsible for injury, particularly in home gardens. Tomato plants in all stages of growth are susceptible to injury from 2,4-D. The degree of injury is directly proportional to the con- centration of the chemical to which the plant is exposed. At high con- centrations when the spray is applied directly to the plant, the first symptoms can usually be seen within 3 to 4 hours. The upper part of the stem becomes twisted and the petioles (leaf stalks) bend down- ward (Fig. 24). The entire plant may die within a week. If the plant This tomato plant was sprayed directly with 2,4-D at a concentration used for weed control. The symptoms of in- jury — drooping and twisting of the upper part of the stem and leaf stalks — appeared 24 hours after it was sprayed. (Fig. 24) survives, the new vine growth is apt to be severely stunted, the stem may split open near the ground, and adventitious roots develop on the side branches above ground. Root growth is severely restricted. There is extensive dropping of flowers. Any fruit that is green at the time of spraying is likely to become heart-shaped or to crack open. (Fig. 25). At lighter concentrations where the fumes or spray mist has drifted several hundred feet before settling on the tomato plant, the first symptoms may not become apparent until 5 or 10 days after Tomato Diseases 35 The cracks in these tomatoes are the result of injury by direct spraying with 2,4-D. The three heart-shaped fruit at the top devel- oped on plants in- jured by 2,4-D mist. (Fig. 25) Upper part of a tomato plant as it looked several days after it was exposed to 2,4-D mist. The wavy margins and drawn out tips of the leaflets are typical symptoms of 2,4-D injury. (Fig. 26) 36 Circular No. 912 spraying or until new leaves have expanded. The leaflets have wavy or frilled margins (Fig. 26) , and the veins are lighter and more prom- inent than usual. The tips of the leaflets tend to be drawn out to a fine point. Fruit may ripen prematurely. The amount of blossom drop and heart-shaped fruit may be considerable but depends on the con- centration of 2,4-D to which the plant has been exposed. At distances of y Hornworms can practically strip a plant of its leaves (A). They are held in check by tiny wasp parasites. Hornworms with parasite cocoons on their backs (B) should not be destroyed, since the hornworms will do no more feeding and the parasites emerging from the cocoons will attack other hornworms. (Fig. 28) Tomato Fruitworms By far the most destructive of the tomato fruitworms is the corn earworm.1 This insect is often referred to simply as the tomato fruit- worm, although the general classification of tomato fruitworms in- cludes several species of cutworms as well. The corn earworm ranges in color from a flesh pink to green or dark brown, with darker stripes running the length of the body. Full-grown worms are usually about \y2 inches long. 1 Heliothis zea (Boddie). 40 Circular No. 912 Injuries on these tomatoes are typical of the damage done by the corn earworm. The fruit is ruined by the feeding of these worms. They may attack the fruit at any stage of its devel- opment. (Fig. 29) Injury. Unlike hornworms, com earworms feed mainly on tomato fruit, attacking fruit of all sizes. They do not confine their feeding to single fruit, but move from one to another, destroying much more than they consume. Damage to the tomato crop (Fig. 29) is greatest when the moths are abundant and the supply of green corn silk is more or less limited. In northern Illinois the greatest injury occurs during the latter part of the growing season. Cutworms sometimes attack tomato fruit, but ordinarily do not do much damage. Life history and habits. The corn earworm does not often over- winter north of the Ohio river. To the south, it spends the winter 2 to 6 inches beneath the soil surface as a brown pupa. The moth which emerges in the spring has a wingspread of about V/2 inches. The wings are dark straw to grayish-brown. The moths lay their eggs on the fresh silks and tassels of corn, on tomato plants and eggplants, and on other host plants, both wild and cultivated. It takes 5 to 7 days for the eggs to hatch. The worms feed for 3 weeks or more before becoming full-grown. During this time each worm injures several fruits. Pupation takes place in the ground soon after the worms become mature. None of the pupae developing in the late fall are able to survive the cold winter in central and northern Illinois. Migrating moths are responsible for the initial tomato fruitworm infestation each year in the northern two-thirds of the state. Control. Regular dusting or spraying of tomatoes for control of the corn earworm or tomato fruitworm is not necessary in northern Illinois until late in the season in years when the insect is abundant in field and sweet corn. However, this insect is damaging in southern Illinois almost every year. Where tomatoes are regularly attacked by Tomato Insects 41 fruitworms, early and thorough treatment is essential for tomatoes free of worms. Make applications of carbaryl as dust or spray at weekly intervals beginning at first fruit set. Carbaryl may be combined with fungicides used in the regular spray schedule, thus saving the expense of a sepa- rate application. Cutworms attacking tomato fruits can also be controlled in this manner. Colorado Potato Beetles The Colorado potato beetle1 is an oval, hard-shelled insect about % inch long, with alternate black and yellow stripes on the wing covers. The full-grown young are sluggish, soft-bodied, humpbacked grubs. They are red with two rows of black spots on each side of the body and are about the same size as the adult beetles. Injury. This beetle is a typical chewing insect. Although it is pri- marily a pest of other crops, it often attacks tomatoes. Both the adults and larvae feed on the foliage and if they are numerous may com- pletely strip the plants. Life history and habits. The Colorado potato beetle overwinters in the adult stage several inches below the surface of the soil. The beetles come out of the soil in the spring to feed and lay cylindrical, orange-yellow eggs. The eggs are deposited in groups of 5 or more on the undersides of the leaves. It takes 4 to 9 days for the eggs to hatch and about 3 weeks for the grubs to become full-grown. These full-grown grubs then descend into the soil, make a spherical cell, and transform to the pupal stage. After 5 to 10 days, the adult beetles appear, feed for several days, and lay eggs for the second generation. Two genera- tions occur annually. Control. The Colorado potato beetle can be easily controlled by carbaryl dusts or sprays. The insecticide should be applied when the beetles or grubs are first noticed. One or two treatments should elimi- nate both the adults and larvae. Garden Slugs Several species of slugs attack tomatoes. Their presence is easily detected by the shiny trails of slime they leave in their paths. These slimy, repulsive creatures resemble snails in general appearance. They range in color from gray to dark blue and are 1 to 3 inches long. Injury. Slugs are most troublesome during seasons when there is a great deal of moisture. They rasp out holes in the foliage and fruit of tomato plants, the principal injury being to the ripening fruit. Blemishes and decay are common on tomatoes that have been attacked. 1 Leptinotarsa decemlineata (Say). 42 Circular No. 912 Life history and habits. Slugs lay their eggs in clusters in moist soil or other protected places. These hatch in three weeks or more, depending upon the weather. Development depends largely upon food and living conditions. Slugs are said to live for several years. Control. Metaldehyde is recommended for the control of garden slugs. Follow the manufacturer's directions in the use of this material. An application of hydrated lime may afford some protection. Cutworms Most growers are familiar with cutworms and the damage they do. Several species of these plump, well-fed worms (Fig. 30) damage tomatoes. Although they vary considerably in habits and appearance, Newly hatched cut- worms are usually darker and more hairy than mature ones. After feeding for about a month they become full grown (b, c, d). Then they change into pupae (co- coons), and remain in this stage about two weeks. Emerg- ing as moths (a), they are ready to lay eggs (e, egg much enlarged; /, egg mass) to start a new generation. (Fig. 30) they are usually gray to brown or black in color and are from 1% to 2 inches long when full-grown. Injury. Cutworms are ordinarily most troublesome during the early spring, doing their damage in the hotbed or in the field and garden soon after transplanting. They may cut the plants off at or near the ground level, feed on the foliage or fruit, or destroy the roots. The cutting off of the young plants is usually the most noticeable injury. Life history and habits. Most of the common cutworms pass the winter in the worm stage. They may be found hibernating in the soil, clumps of grass, or other protected places. Feeding begins early in the spring and continues until the worms become full-grown. Pupation takes place underground. Adult moths emerge during late spring and Tomato Insects 43 commence laying eggs shortly thereafter. Eggs are laid on the ground, and on the stems of weeds, grasses, or other plants. Most of the common cutworms have but one generation a year. Control. Clean cultivation of crops that precede tomatoes is of considerable importance in cutworm control. Sod or weedy ground upon which tomatoes are to be grown the following year should be plowed during late summer or early fall and kept clean in order to keep cutworm moths from laying eggs. In a small garden, cutworms can be collected by hand. Young plants can be protected by pressing tin or cardboard cylinders into the soil around the plants, or by wrapping the stem with a 4-inch collar of paper at transplanting time. One-half teaspoon of granular dieldrin or heptachlor worked into the soil about the base of the plant will protect the newly transplanted plants. Sprays or dust of carbaryl or toxaphene will successfully control cutworms that attack plants above the ground. Treating the above- ground portion of the plant will not control the black cutworm and others that feed underground. For these insects, a soil insecticide must be worked into the soil around the base of the plant. Aphids or Plant Lice Aphids, or plant lice,1 are small, soft-bodied insects that secure their food by sucking sap from the plants. They are about % inch or less in length, and vary in color from solid pink to dark green. Both winged and wingless adults may appear on the same plant. Injury. Aphids are seldom numerous enough on tomatoes to kill the plants. They may, however, stunt the plants and injure the fruit clusters enough to reduce yields. They also transmit virus diseases of tomatoes. Aphids prefer the shaded parts of a plant, but may be found on exposed blossom clusters and growing tips. They feed entirely on juices extracted from plants with their small, piercing mouth parts. Whether grown in the greenhouse or out-of-doors, tomatoes should be carefully watched for aphid infestation and promptly and thoroughly treated if the insects are abundant enough to cause damage. Life history and habits. The potato aphid, which is commonly found on tomato plants, spends the winter in the egg stage on rose bushes. During the summer, winged females are produced that migrate back to tomato, potato, and other plants, where they feed and repro- duce. Both winged and wingless females occur, each capable of giving birth to as many as 50 young over a period of two weeks. Ten days to three weeks are required for the young to reach the adult stage. 1 Macrosiphum solanifolii (Ashm.) and other species. 44 Circular No. 912 During the fall, winged females migrate back to the rose, where a generation of wingless egg-laying females is produced. Several gen- erations are produced each year. Control. Aphids can be controlled on tomato plants by a thorough application of either 40-percent nicotine or malathion dust or spray. Nicotine should be applied only when the temperature is above 70° F. Parathion is also effective on tomato aphids. Avoid overdosing with this insecticide as it may injure tomato plants. When applying para- thion, wear a good respirator or dust mask and protective clothing. Bathe or shower as soon as possible after using this material. The home gardener should not use this material. Whiteflies Greenhouse tomatoes are sometimes infested with tiny, powdery- white insects, known as whiteflies,1 that swarm off the plants when disturbed. The adults, which may be seen at rest on the underside of infested leaves, are about Y1G inch long and have four wings. The young, also found on the underside of leaves, are very small, oval, scale-like creatures, light green in color. Injury. Injury from this pest is common on tomatoes and other greenhouse crops. Both adults and young suck sap from the plants. If the infestation is very heavy, the plants become stunted and unpro- ductive. The young excrete a sticky substance which covers foliage or fruit and supports a growth of black fungus. Life history and habits. All stages of whitefly may be found at any time in an infested greenhouse. The eggs, which hatch in 10 to 14 days, are deposited on the underside of leaves. After hatching, the nymphs attach themselves and begin sucking sap from the plants. They are then oval-shaped, motionless, and light green. About two weeks from the time of hatching, adults emerge and begin at once to lay eggs. Control. Whiteflies can be controlled by an application of dust or spray. Malathion applied in the form of a 10-percent aerosol at a dosage of 1 pound to 50,000 cubic feet is effective in the greenhouse. While applying aerosol in a greenhouse, be sure to protect yourself by wearing a mask recommended to absorb the insecticide. Nematodes or Eelworms Root-knot of tomato is caused by microscopic nematodes,2 or eel- worms. In Illinois these pests cause most trouble in the greenhouse, but may attack tomatoes in the field, especially if the young plants were grown in infested soil. 1 Trialeurodes vaporariorum (Westw.) 2 Species of Meloidogyne Goeldi. Tomato Insects 45 Injury. These very small white worms bore into the roots of tomato and other crops, causing characteristic knots or swellings, as shown in Fig. 31. This abnormal growth of the roots prevents the normal transportation of water and food materials, causing the plants to become stunted and eventually to die. If tomatoes are wilting or dying prematurely, a few plants should be dug up and the roots examined for this trouble. Control. Every precaution should be taken to prevent transfer of nematodes from greenhouses to fields and from one farm to another by movement of soil or by planting infected transplants or tubers. An extreme case of root swelling and distortion caused by the root-knot nematode. Affected plants become stunted and eventually die. (Fig. 31) 46 Circular No. 97 2 Unless greenhouses, hotbeds, and coldframes are known to be free from root knot, the soil should be disinfested (page 49). Steam dis- infestation is preferred for it is not only effective against nematodes but also kills fungus pathogens, insects, and weed seeds. If steam is not available, certain chemicals can be used alone or in combination to fumigate nematode-infested soil. Field or garden soil that is known to be infested should not be planted to tomatoes or other susceptible crops. Symphylids Symphylids1 are primarily greenhouse pests in this state. Tomatoes cannot be grown successfully in houses where the soil is infested with these insects. They are white, centipede-like creatures, about % inch long when full-grown, and may be found to a depth of 3 feet. Injury. By eating off the young roots, these tiny creatures cause plants to become badly stunted and to finally die. They may also attack the larger roots and underground parts of the stem, making them warty and tough. Life history and habits. Throughout the year an infested green- house will contain symphylids in all stages of development. They spend their entire life below the soil surface. Usually they lay their eggs, which are almost invisible to the naked eye, several inches below the surface. It takes 4 to 6 weeks for symphylids to complete their develop- ment from egg to adult. Control. Prevention is better than cure, for once an infestation has become well established in a greenhouse, it is hard to clean up. Symphylids are most easily controlled in raised benches, though even this is difficult. All symphylids and eggs in raised benches can be killed by steam disinfestation if this is properly done. In ground benches, steam disinfestation will kill all symphylids in the upper part of the soil. Since some of the eggs and adults survive in the lower sub- soil, disinfestation will have to be repeated each year in order to pre- vent serious injury. Walks, as well as benches, must be treated. Infestation is sure to occur again in disinfested benches if infested soil is brought in from the outside or other parts of the greenhouse. Lindane gives good control of symphylids. Use 5 ounces of 25-percent lindane wettable powder in 50 gallons of water and apply the mixture wL I to 1,000 square feet. Additional watering will aid penetration. Mites Spider mites and tomato russet mites are sometimes troublesome in commercial plantings. Malathion, kelthane, or parathion give good control of spider mites. Sulfur is very effective against tomato russet 1 Scutigerella immaculata (Newp.). Tomato Insects 47 mites. Use either 10 pounds of wettable sulfur or 30 pounds of sulfur dust per acre. Parathion or kelthane can also be used to control russet mites. When applying parathion, wear a good respirator or dust mask and protective clothing. Bathe or shower as soon as possible after using this material. The home gardener should not use this material. Cloudy Spot of Tomato Fruit Cloudy spot of tomato fruit, caused by the feeding of stink bugs, is one of the most common troubles reported from Illinois home gardens. It is most common from late July or early August until the end of the season when activity and feeding of the stink bugs stop. Although these bugs may be so few in number as to go unnoticed, only a very few are necessary to cause cloudy spots on most tomatoes. Injury. The injuries appear on the green fruit as whitish areas with indistinct borders. Isolated spots may be from l/1G to V2 inch or so in diameter, or the spots may run together and involve a large portion of the fruit surface (Fig. 32). On ripe fruit the spots are light yellow. If the skin is peeled back, the discolored area is seen to consist of shiny, somewhat spongy masses of tissue that do not extend deeply into the fruit. The processor, however, must cut these areas out to get whole canned tomatoes of top quality. Life history. The stink bug overwinters as an adult in debris along fence rows and ditch banks. The adults leave hibernation in early spring to feed and lay eggs in weeds or weedy areas. The bugs, hatched from the eggs, suck plant juices and become full grown in 4 to 6 weeks. In Illinois 3 or 4 generations are probably produced each year. Control. Stink bugs are difficult to control. Weedy areas, such as fence rows and ditch banks, are homes of these insects. Spray weedy areas near commercial gardens with toxaphene. The feeding of stink bugs caused the indistinct whitish or yellowish areas on this tomato. (Fig. 32) 48 Circular No. 912 SEED TREATMENT Tomato seed treatments are of two types: eradicative seed treatment, which destroys disease-producing fungi and bacteria carried with the seed; and protective seed treatment, which coats or "galvanizes" the seed coat, thus protecting the seed against decay and damping-off caused by soil organisms. Both types of treatment are important in producing disease-free tomato plants. Since very few seed-treating materials will serve as both eradicants and protectants, it is usually advisable to follow the eradicative treatment with a protective treatment. Eradicative Seed Treatments Hot water or bichloride of mercury can be used for eradicative treatment. Hot-water treatment will eliminate most internal and ex- ternal seed-borne disease organisms; bichloride of mercury treatment will disinfest only the surface of the seed. Bichloride of mercury is available at any drug store, is relatively easy to use, and is therefore especially recommended for the home gardener. Hot-water treatment. Put the seed in a loosely woven cotton bag, filling not more than half the bag. Then soak the seed for 25 minutes in hot water held at 122° F. It is very important that water be kept at this temperature. If it gets even 2 or 3 degrees hotter, the seed may be injured. For this reason, an accurate thermometer is essential. For best results the volume of water should be at least five times the volume of the seed. When the seed bag is first put in the water it should be worked with the fingers to make sure that all seeds are wetted and that all air is out of the bag. After treatment pour out the seed in a thin layer on paper or screens in a warm but not hot place. CAUTION — All the chemicals used for seed treatment are in- jurious to man and animals when taken internally. Some may cause severe skin irritations if allowed to accumulate. Every pre- caution should be taken to avoid inhaling them. Wear a dust mask or respirator if large quantities of seed are being treated with dusts. Wash exposed skin surfaces at frequent intervals with soap and water. When finished with treatment, pour all chemical solutions down the drain or pour out in such a way that they will soak into the ground. So/7 Disinfestation 49 When the seed is thoroughly dry (24 to 36 hours after treatment) it should have a protective treatment. Bichloride of mercury treatment. This material (also known as mercuric chloride and corrosive sublimate) can be bought in the form of blue tablets or as a crystalline powder. It is mixed with water in a non-metallic container at the rate of 1 to 2000. One tablet in 1 quart of water or l/8 ounce of the powder in 7% quarts of water will give the right proportions. First completely dissolve the chemical in a small amount of boiling water; then add as much cold water as is needed. There should be at least 1 gallon of solution for each pound of seed. Put the seed in a cotton bag and soak it in the solution for 5 minutes. Remove the seed from the solution, let it drain for a few seconds, wash it in several changes of water, and spread it out in a thin layer to dry. After the seed is thoroughly dry, it should be given a protective treatment. A bichloride of mercury solution should be used for only one lot of seed and then discarded. This material is a DEADLY POISON. Before using, read care- fully the precautions on page 48. Protective Seed Treatments Captan 75 (sold under such trade names as Stauffer Captan 75 Seed Treatment, Orthocide 75 Seed Protectant, and Miller's Captan 75), and thiram 75 (sold under such trade names as Arasan 75, Arasan SF-X, Panoram 75, and Thiram 75W) are suggested as protectants against seed decay and damping off. Combinations of a fungicide and an insecticide may be purchased. Fill a jar or can up to half full with seed, add the amount of fungicide recommended on the package label, close lid tightly and shake or roll on floor for 5 minutes or until the seed is evenly coated. To treat in the seed packet, place a small amount of the fungicide on the tip Vi inch of a penknife blade, dump into the slit corner of the envelope, fold the top tightly shut, and shake for a minute or two. The seed can be sown at once or stored for some time if kept dry and in a container that will permit some air circula- tion. Any excess fungicide remaining after treatment can be screened off and used again. SOIL DISINFESTATION When properly done, disinfestation of the soil is one of the most effective ways of controlling soil-borne diseases, nematodes, insects, and weeds. The various methods of soil disinfestation using heat or chemicals are described in detail in Circular 893, "Soil Disinfestation; Methods and Materials.'' This circular can 50 Circular No. 912 be obtained from your farm adviser or by writing to the College of Agriculture, University of Illinois, Urbana, Illinois 61801. FUNGICIDES AND INSECTICIDES Several fungicides and insecticides are suitable for the control of diseases and insects on tomatoes. These materials can be used profitably only if ( 1 ) a spray or dust is selected that is known to control the disease or insect concerned, (2) the plants are uni- formly covered, and (3) applications are properly timed. Most fungicides and insecticides can be combined and ap- plied in one operation, thus saving considerable time and labor. When combining pesticides, use the same proportions as if they were to be applied separately. Spraying gives better control of tomato diseases and insects than dusting, but dusting is valuable when outbreaks of disease and insects threaten and large acreages must be covered quickly. Fungicides The fungicides listed are compatible with most organic insecticides. Regardless of what fungicide is used, read carefully the precautions on the label before mixing and using. Fixed coppers have largely taken the place of bordeaux mixture because they are less apt to cause plant injury and are easier to pre- pare. They can be purchased ready to mix with water for spraying or in a form suitable for dusting. Fixed coppers are sold under various trade names including such forms as basic copper sulfates, basic copper chlorides, copper oxychlorides, cuprous oxides, and copper hydroxides. Zineb is the common name for organic fungicides containing zinc ethylene bisdithiocarbamate. It is sold under such trade names as Dithane Z-78, Parzate Zineb Fungicide, Parzate C, Ortho Zineb 75 Wettable, Chipman Zineb, Niagara Zineb, and Penco Zineb. It can be made in the spray tank by mixing nabam (disodium ethylene bisdithio- carbamate) with powdered zinc sulfate in water. Maneb is the common name for organic fungicides containing manganous ethylene bisdithiocarbamate. It is sold under such trade names as Dithane M-22, Dithane M-22 Special, Manzate D, and Manzate Maneb Fungicide. Ziram is the common name for organic fungicides containing zinc dimethyl dithiocarbamate. It is sold under such trade names as Zerlate « Fungicides and Insecticides 51 Ziram Fungicide, Karbam White, Z-C Spray or Dust, Corozate, Orchard Brand Ziram, Penco Ziram, Ortho Ziram, and Stauffer Ziram. Captan is the common name for organic fungicides containing N- (trichloromethylthio)-4-cyclohexene-l,2-dicarboximide. It is sold under such trade names as Captan 50W, Orthocide 50 Wettable, Orthocide Garden Fungicide, Orthocide Fruit and Vegetable Wash, and Miller's Captan 50W. Daconil 2787 is the proprietary name for an organic fungicide con- taining tetrachloroisophthalonitrile. Difhane M-45 is the proprietary name for an organic fungicide con- taining the coordination product of zinc ion and manganous ethylene bisdithiocarbamate. Polyram is the proprietary name for an organic fungicide contain- ing zinc polyethylene thiuram disulfide. If home-grown plants are used, they should be given one or two applications of fixed copper, zineb, ziram, or captan while in the seed- bed. Maneb may be injurious to young seedlings. Direct-seeded fields should be sprayed or dusted before blocking and thinning. Fungicides applied at this time give protection against collar rot, anthracnose, and early stages of various leaf spot diseases. If late blight or leaf spot diseases appear before flower development, another application of fixed copper, zineb, ziram, or captan may be needed. Insecticides Commercial vegetable gardeners find it impossible to produce vegetables profitably unless they control insects at maximum efficiency and minimum cost. The housewife of today will not accept unsightly wormy vegetables; not only are wormy fruit and vegetables unap- petizing but the waste from trimming increases food costs. Thus the commercial vegetable gardener must produce a quality product that is acceptable and safe to the consumer. Careful and correct use of the right insecticides will enable him to do this. Insecticide recommendations are prepared each year for use by Illinois commercial vegetable farmers; they are not for home gardeners, who should use only those insecticides that are extremely safe to handle, apply, and store. The commercial tomato grower should refer to Circular 897, "Insect Control for Vegetable Crops." The home gardener should obtain circular 900, "Insect Control by the Homeowner." These circulars can be obtained from your farm adviser or by writing to the College of Agriculture, University of Illinois, Urbana, Illinois 61801. 52 Circular No. 912 Spray and Dust Schedules A regular spray or dust schedule with fungicides and insecticides for tomatoes in the field should begin about two weeks after the first crown-cluster flowers appear. Maneb is the preferred fungicide for use in the field, with zineb second. At least four or five applications at 7- to 10-day intervals will be necessary, with the exact number depending on weather conditions. More than five applications may be needed if the weather is cool and rainy, and if late blight is present in the field or general vicinity. Dosage of Insecticides and Fungicides For use on tomatoes for the home gardener, for the fresh market, or for the processor, follow exactly the directions given on the label of the container. CAUTION — All the chemicals used for spraying and dusting are injurious to man and animals when taken internally. Some may cause severe skin irritations if allowed to accumulate. Every pre- caution should be taken to avoid inhaling them. Wash exposed skin surfaces at frequent intervals with soap and water. Bathe or shower and change clothes after applying insecticides or fungi- cides. Zineb is inflammable. To avoid dangers from handling and using these chemicals and to make sure no hazardous residues remain on tomatoes, the directions of the manufacturer should be READ, UNDERSTOOD, AND CAREFULLY FOLLOWED. SPRAYING AND DUSTING EQUIPMENT Home Gardens Manually operated sprayers and dusters are suitable for use in the home garden, where only a relatively small number of plants are grown. Regardless of the type, a sprayer or duster should have enough force to drive the insecticide or fungicide into the center of the plant. A coarse, driving spray may give better coverage of the fruit and inside leaves than a fine, mist-like spray. Frequent agitation of the spray suspensions will be necessary to prevent the pesticides from settling out. Home gardeners will find that prepared mixtures contain- ing insecticide and fungicide are usually available at local pesticide stores. These products are quite effective and are easy to use. The new Spraying and Dusting Equipment 53 ' % J^H - wi 'tifrii* A wide boom is needed on high-pressure sprayers used for tomatoes. This will keep down vine damage and also permit coverage of a maximum num- ber of acres in a day. The sprayer pictured will cover 9 rows. (Fig. 33) granular insecticides in 1-pound containers are particularly adaptable for use in the home garden to control soil insects. Commercial Fields High-pressure sprayers. There are large-volume, high-pressure sprayers which are satisfactory for applying fungicides or insecticides in commercial fields. These sprayers cover as many as 10 rows on one trip across the field (Fig. 33) . In order to use conventional sprayers, some growers have adopted a spacing of 5% to 6 feet between rows, with the plants 2% to 3 feet apart in the rows. These distances provide not only room for wheeled equipment but also more space for pickers to walk and place hampers. Regardless of the type of power-driven, wheeled sprayer employed, certain details must not be overlooked. The nozzle disc should be at least a No. 5 (hole with a diameter of %4 inch). Although discs smaller than No. 5 make pressures easier to maintain, they break up the spray stream into such a fine mist that part of it drifts away and the remainder wets only the outside leaves of the plant. There should be at least three nozzles to each row. Pressures in the spray lines should be at least 200 but not over 500 pounds to the square inch. Speed of operation should not exceed 3 or 4 miles an hour. Proper gallonage can be obtained by regulation of pressure, speed, disc size, and number of nozzles to the row. It is usually necessary to experiment with each sprayer to find the proper regulation. Proper mixing of fungicides or insecticides in the spray tank is necessary for good control of diseases and insects. The tank should not 54 Circular No. 912 im «SL»>«S This mist-concentrate sprayer will cover 20 or more rows of tomatoes in one round trip across a field. Sprayers of this type carry less water than high- pressure sprayers and thus are lighter in weight. (Fig. 34) be more than half full when the pesticide is added. It is advisable to make a thin paste of the fungicide with water in a pail before pouring it into the tank. After thorough mixing in the tank, which means running the sprayer agitator for at least one minute, the rest of the water is added and agitation continued for another minute or two before spraying is started. Low-gallonage, mist-concentrate sprayers. These sprayers have a high-speed, motor-driven propeller which blows water droplets con- taining fungicides to the plants (Fig. 34). The concentration of the fungicide is usually increased over that prepared for a high-gallonage sprayer. Thus if 3 pounds of a fungicide in 160 gallons of water is applied per acre with a conventional, high-gallonage sprayer, then the concentration must be increased in the low-gallonage sprayer to 2 X (3 pounds in 80 gallons) , 4 X (3 pounds in 40 gallons) , or 8 X (3 pounds in 20 gallons) in order to achieve comparable disease control. The amount of water used per acre will depend on pump and nozzle capac- ity, as well as speed. This type of sprayer is lighter in weight and covers a wider swath than the high-pressure sprayer. Spray-deposit tests indicate that fairly uniform coverage of foliage and fruit can be obtained if these sprayers are carefully operated. Dusters. Power dusters for use on tomatoes should have two or three outlets to the row and should discharge equal quantities of dust from each outlet. Dusters have been developed which put out the same amount of dust regardless of whether the dust hopper is full or one-fourth full. Fungicidal dusts should be applied at the rate of at least 50 pounds to the acre if conventional ground equipment is used. Spraying and Dusting Equipment 55 Dew does not have to be present but if the wind is strong enough to prevent complete coverage, dusting operations should be suspended. Airplanes. Airplanes have been used in some instances for applying fungicides and insecticides to tomatoes. Airplane dusting may be of considerable value in combatting late blight where large acreages have to be covered in a short time. The fungicide dosage should be between 60 and 70 pounds to the acre. The application of liquid fungicides to tomatoes by airplanes cannot be recommended at present. How to Send Diseased Plants for Identification If a disease appears in your tomatoes that you can't diagnose from the information in this circular, you may send a specimen from the dis- eased plant to the Department of Plant Pathology, University of Illinois, Urbana, Illinois. Select representative samples of the diseased material you want iden- tified and, if possible, a sample of similar material from a healthy plant. Send plenty of material. A small specimen often fails to show a sufficient range of symptoms to make accurate identification possible. Leaves. Press flat between several sheets of newspaper or paper toweling, place between two layers of cardboard, and mail in an enve- lope. Do not moisten the paper or the plant. Fruit. Send fresh fruit showing symptoms. Do not send fleshy fruit in advanced stages of decay. Wrap separately in paper toweling or news- paper and pack in a strong cardboard box. Do not pack in foil, moistened paper, cotton, or a plastic bag. Roots, stems, or entire plants. Wrap moistened paper toweling tightly around roots. Wrap stems or entire plants in dry paper. Do not moisten tops of plants. Mail in a strong cardboard box. If possible, mail all specimens so that they reach the University no later than a Thursday. Specimens that lie in the post office over a week- end are likely to spoil. Since letters and specimens mailed separately are apt not to arrive at the same time, a letter should be enclosed with the specimen or attached to the package. The letter should give the variety of the plant involved, a description of the disease, weather, and soil condi- tions, and the kind and amount of fertilizers, fungicides, insecticides, and other chemicals that may have been applied to the soil or plants. Don't forget your return address. 6M— 6-67— 93160 UNIVERSITY OF ILLINOIS-URBANA 3 0112 004557465