The disease is more troublesome in heavy, poorly drained soils during prolonged warm wet weather.īacterial Spot (bacterium – Xanthomonas campestris pv. The fungus lives in the soil and it can also affect pepper. The surface of the lesion is usually smooth and firm. Later, dark zonate bands can be seen on the surface of affected areas. Buckeye rot is first noticed as a light green water-soaked area on the fruit. The fungus is different from the one causing late blight, which affects both leaves and fruit. The best control of this disease is by using a preventative fungicide program at 7 to 10 day intervals, the same as used for late and early blight control.īuckeye Rot (fungus – Phytophthora parasitica): This disease occurs on tomato mainly on the fruit, particularly where it touches the soil. Infection occurs readily, and the disease becomes established in the fields quickly. The fungus produces abundant spores during periods of high temperature and very high relative humidity. When conditions are proper for fungal development, large areas of the field are infected, plants are weakened and the crop is greatly reduced. Under humid conditions, the lower surface of these spots become covered with a gray, velvety growth of the spores produced by the fungus. At first, diffuse whitish spots appear on the upper surfaces of older leaves these rapidly enlarge and become yellow. Leaf-Mold (fungus – Fulvia (Cladosporium) fulvum): Leaf mold is usually first observed on older leaves near the soil where air movement is poor and humidity is high. Resistant varieties should be used when possible. Control measures include crop rotation, seedbed sanitation and preventative fungicide applications as for the control of late and early blight. The fungus overwinters primarily on diseased refuse spread is by airborne spores from diseased to healthy plants. They become glazed and at times the centers crack and tear across. These spots usually remain small, but may enlarge until they are about one-eighth inch in diameter. Gray Leaf Spot (fungus – Stemphylium solani): First infection appears as minute, brownish-black specks on the lower leaves that extend through to the undersurface of the leaf. Control practices include the use of disease-free transplants and regular preventative fungicide applications during the growing season. Infection of young seedlings usually results from fungi and soil it occurs principally during periods of high humidity and warm temperature. The fungus is cosmopolitan, affecting a wide range of plants and is present in and on the seed and on crop refuse. Lesions attain considerable size, usually involving nearly the entire fruit concentric rings are also present on the fruit. The fungus also infects the fruit, generally through the calyx or stem attachment. Transplants showing infection by the late blight fungus often die when set in the field. Lesions on the stems are similar to those on leaves, sometimes girdling the plant if they occur near the soil line. If high temperature and humidity occur at this time, much of the foliage is killed. Tissue surrounding the spots may turn yellow. Spots enlarge, and by the time they are one-fourth inch in diameter or larger, concentric rings in a bull’s eye pattern can be seen in the center of the diseased area. Applications should continue on a 7 to 10 day schedule until harvest.Įarly Blight (fungus – Alternaria solani): Early blight is first observed on the plants as small, black lesions mostly on the older foliage. Spraying should begin whenever weather conditions are favorable for disease development. Crops should be sprayed regularly with a fungicide. Control practices include rotating fields so as not to follow potato or tomato avoiding planting tomatoes near potatoes using disease-free seed and transplants. Infection on tomatoes may occur from nearby potato fields or from airborne spores. Hot and dry weather reduces disease development. Ideal conditions for late blight development are cool nights and moderately warm days with abundant moisture. These spores infect healthy leaves, stems and fruit readily if climatic conditions are optimum. The fungus produces abundant numbers of spores which may be splashed by rains or be airborne. White moldy growth may also appear on fruits under humid conditions. Fruit lesions occur as large, green to dark brown lesions, mostly on the upper half of the fruit, but they may also occur on other parts. The disease spreads rapidly under humid conditions, destroying quickly large areas of tissue. These areas enlarge rapidly, becoming brown, and under humid conditions, develop a white moldy growth near the margins of the diseased area on the lower surface of the leaves or on stems. Late Blight (fungus – Phytophthora infestans): Lesions produced on the leaves are at first irregular, rather large, greenish-black and water-soaked.
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