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fungaldiseasesofvegetables-tomato-211210061001.pdf

  1. Fungal diseases of vegetables Tomato Vaishali S.Patil Professor, Department of Botany Shri Shivaji College of Arts, Commerce & Science Akola
  2. 1.Alternaria stem canker caused by Alternaria alternata f.sp. Lycopersici Symptoms-Dark brown cankers with concentric rings form on stems and are often associated with wound sites. These cankers may enlarge, eventually girdling the stem and killing the plant. A brown, dry rot develops and brown streaks can extend into the pith above and below the cankers. A toxin produced by the fungus growing in the stem canker moves into the upper part of the plant, killing the interveinal leaf tissue. As the disease progresses, curling of leaf margins and eventual death of the leaf occurs. Fruit symptoms initially appear as small, gray flecks which later enlarge and become dark and sunken with the characteristic concentric rings. Control: Resistant varieties should be used.
  3. 2.Anthracnose caused by Colletotrichum coccodes, Colletotrichum dematium, Colletotrichum gloeosporioides, Glomerella cingulata Symptoms- On ripe fruit small, sunken, circular spots appear. The center of older spots later become blackish. Spots may become numerous in severe cases, and secondary rotting organisms may invade anthracnose lesions to completely rot infected fruit. The fungus forms small, dark survival structures called sclerotia in the centers of fruit spots. Control: Harvest fruit as soon as possible after ripening. Avoid excessive overhead irrigation or use drip irrigation, use of fungicides, crop rotation.
  4. 3. Black mold rot- caused by Alternaria alternata, Stemphylium botryosum, Pleospora tarda, Stemphylium herbarum, Pleospora herbarum, Pleospora lycopersici, Ulocladium consortiale, Stemphylium consortiale Symptoms-black lesions known as blossom end rot appear on fruit & on the stem. Lesions may look shallow and superficial or sink deep into the inner fruit which turns dark black. Control: fungicides
  5. 4.Black root rot caused by Thielaviopsis basicola, Chalara elegans Symptoms-Stunting, yellowing of leaves, and lack of vigorous growth. Roots of affected plants had numerous small, brown lesions. Control: -Maintaining a soil pH below 5.6, removing and destroying all diseased plants, using soil-less media, sterilizing equipment, keeping work areas clean, and controlling fungus gnats and shore flies, “crop rotation, soil fumigants.
  6. 5.Black shoulder caused by Alternaria alternata Symptoms-on leaves as spots that range in size from tiny to the width of thumb. They are usually yellow or brown and once they appear, they spread rapidly in concentric rings of darkening color. Spots usually transfer or begin appearing on fruit and seed pods at about the time they appear on leaves. Control: infected plants should never be composted, fed to livestock, or otherwise consumed,wider spacing, clear weeding, and plant staking to allow air flow, use of organic fungicide.
  7. 6. Buckeye rot of tomato caused by Phytophthora capsici Phytophthora drechsleri, Phytophthora nicotianae var. Parasitica, Phytophthora parasitica Symptoms- grayish-green or brownish, water-soaked spots developing on fruit. The spot rapidly enlarges to cover up to half of the fruit diameter. The rot then appears brown with concentric rings. Control: site selection, staking, mulching, cultural practices, crop rotation, fungicides.
  8. 7.Cercospora leaf mold caused by Pseudocercospora fuligena, Cercospora fuligena Symptoms- chlorotic (yellow) lesions which are visible on the upper side of the leaf that later expands to form a brownish lesion surrounded by a yellow halo. When the humidity is high, gray to blackish-gray fungal sporulation occurs on the lower leaf surface. When the disease is severe the lesions will coalesce, resulting in the collapse of the leaf tissues. Control: sanitation, crop rotation till and fungicides
  9. 8. Charcoal rot caused by Macrophomina phaseolina Symptoms- On seedlings, black, sunken cankers may appear on hypocotyls at the time of emergence. These cankers may develop a concentric ring pattern, stunt affected plants and cause wilt. When older plants are attacked, runners and crown leaves may turn yellow and die. Typically, a water-soaked lesion will occur at the soil level and extend several centimeters up the stem. Brown, water-soaked lesions are also symptomatic of fruit infection. Amber-colored droplets of exudate may form within the affected area. Eventually, the lesion dries up, turns light tan and microsclerotia form. Control: Manage irrigation to avoid drought stress. If soil salinity is high, leach to reduce salt buildup. Drip irrigation may result in higher soil salinity compared to furrow irrigation if salinity of the irrigation water is moderate to high. Destroy or deep-plow all plant debris at the end of the season, a three-year rotation.
  10. 9. Corky root rot caused by Pyrenochaeta lycopersici Symptoms-Extensive brown lesions, often arranged in bands with lengthwise cracking of the cortex, develop on the larger roots. The tips of infected older roots are pinched off. Small feeder roots may be completely decayed. Infected plants are stunted and slow-growing. Branches on mature plants may die back from the tips. Control: Cultural practices, soil fumigation on fields, plant when soils are warm in spring, avoid consecutive crops, soil solarization, rotate with nonhost crops, use of metam sodium.
  11. 10. Didymella stem rot caused by Didymella lycopersici Symptoms-The lesions can be noticed as dark sunken and usually girdle the stem. The entire plants can turn yellow and wilt. Fruiting bodies of the fungus (pycnidia) are black in color and numerous on lesions. As the wilting progresses, the plant may eventually die. Numerous black specks (pycnidia), which are the fruiting structures of the fungus, frequently form in the darkened stem lesions. Fruit infection typically occurs at the calyx end and starts as a water soaked lesion that progresses rapidly into a sunken black lesion with concentric rings. Leaf infection begins as small spots, which develop into brown lesions with concentric rings. Pycnidia may develop in the center of these lesions with the leaf eventually taking on a shot hole appearance, or dying. Control: Fungicide, sanitation , three-year rotation, avoid overhead irrigation and provide adequate Ventilation.
  12. 11. Early blight caused by Alternaria solani Symptom-Extensive defoliation from early blight exposes fruit to sunscald and increases fruit rot. It also attacks stems and fruit. Dark brown cankers may develop on stems and girdle stems of seedlings at the soil line. Stem lesions on older plants usually remain confined to one side of the stem. Infected leaves show circular spots (lesions) that are brown and have a pattern of concentric rings imparting a “target-like” appearance to the spot. The leaf area surrounding these spots may turn yellow. Infected leaves eventually turn brown and drop from the plant. Defoliation progresses upward from the lower plant. Sunken, dry lesions occur most frequently on the stem end of the fruit and also have a zonate or “target-like” appearance. Control: Crop rotation. Avoid prolonged wetting of leaves from irrigation or use drip irrigation. Maintain adequate, but not excessive, soil fertility. Use of proper fungicide.
  13. 12. Fusarium crown and root rot caused by Fusarium oxysporum f.sp. radicis-lycopersici Symptom-brown vascular tissue in stem from crown to slightly above; stem surface can be brown; roots are brown and rotting. Control: Use disease-free transplants, avoid over watering, disinfect transplant trays by steaming, use a preplant fumigant, avoid injuring transplants, rotate with a nonsusceptible crop, use of biological control, cover crops, and soil solarization alone or in combination with fumigants.
  14. 13. Fusarium wilt caused by Fusarium oxysporum f.sp. Lycopersici Symptom -A yellowing of the lower leaves, which gradually wilt and die. The disease progresses up the stem until all of the foliage is killed and the plant dies. If stems or petioles from wilted areas of diseased plants are cut, a reddish-brown discoloration can be seen between the pith (center of the stem) and the outer green part of the stem. It is soilborn & seedborne disease. Control: Use of resistant varieties, crop rotation
  15. 14. Gray Leaf Spot caused by Stemphylium botryosum f.sp. Lycopersici, Stemphylium lycopersici, Stemphylium floridanum, Stemphylium solani Symptoms- Small brownish-black flecks that extend to both sides of the leaf. Spots may be bordered by a narrow yellow halo. As the spots enlarge, the central portion becomes gray, cracks and falls out imparting a shot-hole appearance to affected leaves. Leaves with numerous spots turn yellow and drop to the ground. Control: Use of susceptible variety, cultural and chemical controls.
  16. 15. Gray mold caused by Botrytis cinerea, Botryotinia fuckeliana symptoms: Tan or gray lesions typically form at the tips of leaflets and become covered with brown or gray fungal growth. Dead flowers and dying calyx tissue may also become infected. Stem cankers may also develop. Typically large, brown cankers may girdle the stem, causing wilting and plant death above the canker. The production of “ghost spots,” small, whitish rings or halos that develop on the fruit. Fruit that does become infected becomes water-soaked and soft. Control: reduce leaf wetness, proper pruning, sanitation, fungicides
  17. 16. Late blight caused by Phytophthora infestans Symptoms- appear on the upper surface of leaves as greasy, gray spots that expand rapidly. White mold usually develops at the margins of affected areas. If stems and petioles are infected, areas above these infections wilt and die. Entire plants may be rapidly defoliated when conditions favor the disease. Fruit infections begin as brown, greasy spots that rapidly expand to rot the entire fruit. Control: Dead vines from previous crops should be removed or destroyed, avoid use of sprinkler irrigation, use of fungicide.
  18. 17. Leaf mold caused by Fulvia fulva, Cladosporium fulvum symptoms are pale green or yellowish spots on the upper leaf surface, which enlarge and turn a distinctive yellow. The spots on the lower leaf surfaces become covered with a gray, velvety growth of the spores produced by the fungus. When infection is severe, the spots coalesce, and the foliage is killed. Occasionally, the fungus attacks stems, blossoms and fruits. Green and mature fruit can have a black, leathery rot on the stem end. Control: Crop residue should be removed from the field. Staking and pruning to increase air circulation, avoid wetting leaves when watering, crop rotation, use of fungicide.
  19. 18. Phoma rot caused by Phoma destructiva symptoms -In its earliest stages, green fruit is marked by minute, slightly sunken spots. As these spots enlarge they develop brown or black borders with slightly lighter centers which become dotted with black pimple-like bodies (pycnidia) in which the seedlike bodies, or spores, of the fungus are borne.On the plant; spots are seen on the leaves, leaf petioles, and the stems of the vines. Spotted leaves dry out and are shed. In the early stages the spots on the leaves are mereiy small discolored areas, later turning brown or black, which are definite in outline. These spots enlarge, and often several merge into a large blotch. On petioles and stems the diseased areas appear as streaks or blotches. Control: fungicide, Crop rotations, disease-free seed, diseased parts are cut away.
  20. 19. Powdery mildew caused by Oidiopsis sicula, Leveillula taurica symptoms: Powdery white patches of fungal mycelium develop on the upper surfaces of infected leaves. These leaves may become chlorotic and eventually necrotic. Light green or bright yellow, irregularly shaped lesions typically appear on the upper surfaces. Control: resistance, fungicides
  21. 20. Pythium damping-off and fruit rot caused by Pythium aphanidermatum, Pythium arrhenomanes, Pythium debaryanum, Pythium myriotylum, Pythium ultimum Symptom- A small water-soaked spot appear on fruit. At severity the entire fruit becomes rotted, the skin ruptures and the watery contents of the fruit spill out. A white, cottony growth may be observed within rotted areas of the fruit. Control: Start seeds indoors in sterilized potting mix. Do not start seeds in soil that has a high nitrogen level. Add nitrogen fertilizer after the seedlings have produced their first true leaves. Allow the surface of the soil to dry between waterings.
  22. 21. Rhizoctonia damping-off and fruit rot caused by Rhizoctonia solani,Thanatephorus cucumeris Symptom- Alternating light- and dark brown colored zonate bands and sharply defined margins appear on fruits. The rot may be firm at first, but later, affected fruit becomes mushy. Control: Avoid planting tomatoes in poorly drained soils or in low areas of a field. Mulching with plastic film or with organic matter to keep fruit from contacting the soil and/or to reduce soil splashing onto fruit will reduce the chance of soil rot infection. Use of fungicide spray.
  23. 22. Rhizopus rot caused by Rhizopus stolonifer Symptom-water soaked regions on the fruit leading to puffy white growth that collapses the outer fruit tissue. The white fungal mycelia can be noticed with large masses of black mustard like spores on raised stalks. Control: Postharvest fungicide applications are effective. Avoid injuring fruit during harvesting and handling and maintain proper temperature control during storage and transit.
  24. 23. Septoria leaf spot caused by Septoria lycopersici Symptom-The disease first appears on the lower leaves after the plant has set fruit. Leaf spots begin as yellow areas that later become circular with gray centers and dark borders. Spots surrounded by a yellow halo. Tiny black specks may develop in the center of these spots. These are fruiting structures that release spores. Severely infected leaves fall off. Defoliation progresses from the base of the plant upwards. Loss of foliage may cause fruits to become sunscalded. Control: Crop rotation, removal of plant residue, Weed control, use of proper fungicide.
  25. 24. Sour rot caused by Geotrichum candidum, Galactomyces geotrichum, Geotrichum klebahnii (= G. penicillatum) Symptom-It usually begins at the stem scar and may extend in sectors down the side of the fruit. A dull white fungal growth may occur where the epidermis cracks. The fruit often remains firm until the rot is advanced, and then a sour odor develops. Control: Avoid fruit injury, especially at harvest. Cultural methods, which keep fruit from coming in contact with the soil, help prevent many of the fruit rots. Improve air movement in the field by orienting planting rows in the direction of prevailing winds, and use proper row and plant spacing to shorten the length of time that the fruit remains wet. Schedule sprinkler irrigation to minimize the length of time that free water remains on the fruit. Fungicides may offer some protection against some fruit rots. Firm fruited, crack-resistant varieties may escape infection by some fruit rots.
  26. 25. Southern Blight caused by Sclerotium rolfsii, Athelia rolfsii Symptom- Rapid wilting of the entire plant take place. A water-soaked lesion on the stem near the soil line rapidly expands, turns brown and girdles the stem. A white mold (mycelium) eventually covers the stem lesion and surrounding moist soil. Sclerotia form on the mycelium which is first white, later becoming brown. It is soilborn disease. Control: Crop rotation, use of fungicide, removal of plant residues.
  27. 26. Target spot caused by Corynespora cassiicola Symptoms on leaflets begin as small, water-soaked lesions that expand and become light brown and circular. These lesions often develop a target-like appearance. Yellow halos develop around individual lesions. Lesions may coalesce and result in the collapse of leaflet tissue. Similar lesions develop on petioles and stems, but these are more elongate than those on leaves. These lesions may girdle petioles and stems and result in leaflet or leaf collapse. On young fruit, lesions begin as brown, sunken spots the size of a pinpoint, but they can develop into craters. On ripe fruit, large, circular lesions with brown centers can develop. A crack often develops in the centers of the lesions on ripe fruit. Control: Fungicides
  28. 27. Verticillium wilt caused by Verticillium albo-atrum, Verticillium dahliae Symptom- They block the vascular tissue in the plant and cause the leaves and stems to wilt. Symptoms progress slowly, often one stem at a time. Eventually, the entire plant yellows and withers. Control: Plant only resistant varieties. Soil solarization will help kill the fungal spores, crop rotation.
  29. 28. White mold caused by Sclerotinia sclerotiorum, Sclerotinia minor Symptoms: Water-soaked areas near leaf axils or in stem joints are form. Stems become soft once infected and eventually become light gray or tan and have a bleached appearance. Mycelium often develops on or in infected stems. Black sclerotia that look like rat droppings are often present on the fungal mycelium or inside infected stems. These sclerotia are typically black on the outside and white on the inside. Infected fruits typically turn gray and develop a watery rot. The characteristic white fungal mycelium and black sclerotia may also develop on infected fruits. Control: cultural practices, deep-plowing, fungicides.
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