cucurbits vadivel_chellam

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Published on September 28, 2007

Author: vadivel007

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PowerPoint Presentation: PAT-301 DISEASE MANAGEMENT (2+1) DISEASE OF CUCURBITS Assignment on PowerPoint Presentation: DOWNY MILDEW DOWNY MILDEW : DOWNY MILDEW Downy mildew, caused by the fungus Pseudoperonospora cubensis , is primarily an airborne fungus that can cause considerable damage during periods of moist, cool weather This disease produces irregular to angular yellow to brownish areas on the upper side of diseased leaves The underside of the leaves may show a pale grayish-purple mold after damp weather Contin..: Contin.. The mold may vary from white to nearly black in color. The diseased spots may enlarge rapidly during warm, moist weather, causing the leaves to wither and die. This damage may resemble frost injury because the entire vine is killed. The fruit from diseased plants is usually small and of poor quality. Contin..: Contin.. Follow the same spray program recommended for scab control. Fungicides containing mefenoxam have been the most effective fungicides for control of downy mildew. However, fungal insensitivity to these fungicides has been observed, and switching to chlorothalonil products has been recommended when this problem is observed PowerPoint Presentation: POWDERY MILDEW PowerPoint Presentation: cichoracearum , is much more widespread on cucurbits than downy mildew, especially during dry, hot periods. This disease is characterized by a white or brownish mealy growth found on the upper and lower sides of the leaves and young stems If plants are severely attacked, the leaves and young stems may wither and die. In less severe cases, the plant may be weakened or stunted. Early defoliation resulting from the disease may cause premature ripening or sun scald. PowerPoint Presentation: The use of preventive fungicide applications is the most effective means of suppressing powdery mildew. Fungicides used in conjunction with resistant varieties offer the most complete disease management program for powdery mildew on cucurbits PowerPoint Presentation: Cucurbit seedlings infected with Fusarium crown and foot rot Crown necrosis, often with visible fungal growth ANTHRACNOSE : ANTHRACNOSE Anthracnose can be very destructive on cantaloupe, cucumber and watermelon. Pumpkin and squash are rarely affected, except where overripe fruit is left in the field or garden. Losses of fruit in storage or shipment can occur when freshly harvested fruit becomes infected. MODE OF SPREAD : MODE OF SPREAD The causal fungus ( Colletotrichum lagenarium ) survives between crop seasons in infected plant debris as well as on and in cucurbit seed. The disease develops rapidly when moisture is high, and the spores are spread from plant to plant by splashing rain, cultivating tools, clothing and insects. The spores can infect any exposed part of the plant and symptoms usually develop within a few days. CONTROL: CONTROL 1.Use commercially produced, disease-free seed. 2.Rotate cucurbits with unrelated crops. 3.Clean up cucurbit fields at the end of the growing season by removing and destroying or plowing under crop debris. 4.Apply approved fungicides to the crop at regular intervals. You can get current spray recommendations from your Cooperative Extension office. 5.Use resistant varieties (like Charleston Gray watermelon) whenever they are available. PowerPoint Presentation: ANTHRACNOSE PowerPoint Presentation: ANTHRACNOSE ANTHRACNOSE : ANTHRACNOSE Alternaria leaf spot is caused by Alternaria spp. and can cause serious damage under extended periods of wet weather. The occurrence of this disease in Georgia is sometimes sporadic but can be devastating if left unchecked. The disease causes tiny brown spots that enlarge on the leaves, causing a target spot with concentric rings. Older lesions will develop a dark color in the concentric pattern Contin..: Contin.. The dark color is caused by spore production, which can cause new infection sites if no protective measures are taken. Most fungicides used in disease management will suppress Alternaria leaf spot; products containing chlorothalonil are generally the most effective. No resistant cultivars are available. PowerPoint Presentation: ANTHRACNOSE ANGULAR LEAF SPOT : ANGULAR LEAF SPOT Angular leaf spot is a cucumber disease caused by the bacterium Pseudomonas lachrymans . The disease produces angular water-soaked leaf spots which may appear "greasy" green. The spots are restricted by the main veins. Later, the spots turn brown, dry up, and develop ragged tears in their centers. Contin…: Contin… In rainy weather a creamy bacterial ooze forms in droplets on the spots. Stems and fruits are also infected. The spots on fruits are small and circular; later they crack open and turn white ANGULAR LEAF SPOT : ANGULAR LEAF SPOT Contin…: Contin… Angular leaf spot bacteria overwinter on the seed and on diseased cucumber refuse in the field. The bacteria are spread by splashing rain and by individuals working among the vines when they are wet. The disease is favored by warm rainy weather. Control angular leaf spot by planting good quality seed. Destroy crop refuse in the fall. Use crop rotation -- if possible, don't plant cucumbers on the same land more often than once in two-three years. Use a copper fungicide when the weather is wet and the temperatures are above 75 F. Avoid overhead irrigation BACTERIAL WILT : BACTERIAL WILT Bacterial wilt is a common, often destructive, disease of cantaloupe and cucumber. This disease can cause nearly complete losses of a planting before the first harvest. Squash and pumpkin are also susceptible, but damage to them is usually less severe. Symptoms: Symptoms The term "wilt" perfectly describes this disease. Individual leaves become dull green and wilt soon after infection. These first symptoms are often associated with insect feeding damage. As the disease progresses, more leaves wilt and eventually the entire vine is affected. Finally, the leaves and vines shrivel and die. Even the fruit on affected vines shrivels. Contin..: Contin.. Field diagnosis of bacterial wilt can be confirmed using a simple "bacterial ooze test. " With a sharp knife, cut through a wilted vine near the crown. Touch the edge of the knife to the surface of the cut end and then slowly pull the knife away from the stem. If the bacterial wilt organism is present, fine thread-like strands of a sticky bacterial slime can be drawn out of the cut end. Contin..: Contin.. The bacterial ooze test works well for cucumber and cantaloupe but is less reliable for squash or pumpkin. For these crops, place pieces of stem into a glass of water. if this disease is present, bacterial ooze will flow into the water. FUSARIUM WILT: FUSARIUM WILT Symptoms of Fusarium wilt differ from bacterial wilt in that a general yellowing of foliage usually precedes wilting. However, sometimes a sudden wilt occurs without any yellowing of foliage occurs. Fusarium wilt is usually more severe later in the season because of the stress of fruit load. Vascular discoloration may or may not occur PowerPoint Presentation: FUSARIUM WILT PowerPoint Presentation: CROWN ROT PowerPoint Presentation: Crown rot is caused by the fungus Phytophthora capsici and may cause serious damage once established. The fungus infects all above ground plant parts of cucurbits SYMPTOMS: SYMPTOMS Symptoms on cucurbits appear as constricted, water-soaked lesions near the base of stems that are in close proximity to the soil. Infected fruit may have circular, sunken, water-soaked lesions, which may contain a pasty or powdery sporulation of the fungus PowerPoint Presentation: Rotation with a non-susceptible crop has been highly effective in disease prevention. It is not advisable to plant a susceptible crop in an infested field for two years. Measures that ensure good field drainage such as using crowned beds, subsoiling and avoiding over-irrigation will lessen the severity of disease. Preventive applications of some fungicides have shown some promise SCAB: SCAB Scab, caused by the fungus Cladosporium cucumerinum , inflicts severe losses on melons in all areas where moisture is high and temperature is relatively low (70° to 75°F). Most damage occurs in North Georgia, where weather conditions are more favorable for disease development. However, damage to fall melons in South Georgia can occur. The fungus causing scab lives over winter in old cucurbit vines and on infected seed. Contin..: Contin.. Early spring infection may come from either of these sources. Spots are produced soon after the fungus begins to sporulate; spores are spread by insects, clothing or tools, or are blown long distances in moist air. PowerPoint Presentation: SOUTHERN BLIGHT PowerPoint Presentation: The soilborne fungus Sclerotium rolfsii causes Southern blight of cantaloupes and melons. This disease is particularly damaging to fruit lying on moist soil during periods of warm weather. Contin...: Contin... Coarse white mycelium and reddish tan sclerotia are characteristic signs of the disease. Infected tissue is usually water soaked and disintegrates rapidly. Extensively damaged fruit will collapse upon handling. BELLY ROT: BELLY ROT Symptoms may vary from small, yellow sunken areas to large rotted spots on the undersides of fruit. Pythium causes a water-soaked lesion that develops into a watery soft rot. White, cottony mycelium is also generally associated with Pythium lesions. Rhizoctonia belly rot typically appears as dry, sunken cracks on the underside of cucurbit fruit. Contin..: Contin.. Rotation and deep turning are cultural practices that can reduce the amount of disease inoculum near the soil surface. Practices that ensure good drainage can also reduce losses to these fungi. Systemic fungicides may aid in suppression of Pythium; fungicides have proven to be inconsistent in dealing with Rhizoctonia belly rot. GUMMY STEM BLIGHT : GUMMY STEM BLIGHT Gummy stem blight, caused by Didymella bryoniae, attacks primarily the leaves and stems of cucurbits and is one of the most destructive diseases of cucurbits in the state. This disease is driven by cool moist periods, especially extended periods of leaf wetness. The gummy stem blight fungus can easily be brought into a new area on or in the seed. Once the disease becomes established, it produces millions of sticky spores. These spores are spread over the field as people, animals and machines move through wet vines. PowerPoint Presentation: GUMMY STEM BLIGHT PESTICIDE APPLICATION: PESTICIDE APPLICATION Two types of sprayers, boom and air-assisted, are used for applying insecticides, fungicides, herbicides and foliar fertilizers. The air-assisted sprayer uses a conventional hydraulic nozzle plus air to force the spray into the plant foliage. Boom sprayers get their name from the arrangement of the conduit that carries the spray liquid to the nozzles. Booms or long arms on the sprayer extend across a given width to cover a swath as the sprayer passes over the field. PowerPoint Presentation: AIR-ASSISTED SPRAYER PowerPoint Presentation: BOOM SPRAYERS PowerPoint Presentation: Development of disease-resistant cucurbits

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