![]() ![]() 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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