![]() Plow or rototill to bury the remaining crop refuse. Remove and destroy tomato vines in the fall. Plant tomatoes in the same place only once in three or four years. When conditions are favorable, the disease may progress very rapidly.Īvoid these diseases by rotating crops. At first, the spots are gray-green and water-soaked, but they soon enlarge and turn dark brown and firm, with a rough surface. In wet weather, the spots may have a downy, white growth on the lower leaf surface near the outer portion of the spot. Dark-green to nearly black wet-looking spots begin spreading in from the leaf edge. Late blight, caused by the fungus Phytophthora infestans, occurs in moist weather with cool nights and moderately warm days. The fungus overwinters on old tomato vines and on weeds in the nightshade family. This disease is most common late in the growing season. Infected fruits often drop before they mature. It occasionally attacks the fruit, producing large sunken black target spots on the stem end of the fruit. Early blight fungus also infects stems and may produce stem cankers. The leaf area around each target spot turns yellow, and soon the entire leaf turns yellow and drops. Concentric rings develop in the spot forming a bull’s eye. It overwinters on tomato and weed refuse.Įarly blight, caused by the fungus Alternaria solani, appears on the lower leaves, usually after a heavy fruit set. The fungus is spread by splashing water and by working among the plants when they are wet. All the leaf loss reduces fruit yield and quality, and exposed fruits are more susceptible to sunscald. Septoria leaf spot, sometimes called Septoria blight, is caused by the fungus Septoria lycopersici and usually appears on the lower leaves after the first fruits set. All are fungal diseases spread by spores, which require dew or rain to infect the plant. There are three major blights that can attack your tomatoes: Septoria leaf spot, early blight and late blight. ![]() Is there anything we can do to keep them from getting it again? - Mrs. Our tomatoes have had blight the last two years. Pruning off low leaves can slow the spread of the disease by reducing the number of spores present.Q. Invisibly small spores are spread to new leaves by wind, rain and insects, where warm, damp conditions encourage them to germinate and grow. When watering tomatoes, avoid wetting the foliage. Use mulches to keep soil from splashing onto tomato leaves. In early summer, clip off the first spotted leaves when you see them, and compost them in an active compost pile. Grow tomatoes at wide spacing in full sun, so their leaves dry promptly each morning and after rains. Try resistant varieties, which are new but very worthwhile. Most of the time early blight weakens plants but does not kill them. Tomatoes can tolerate losing some of their low leaves to early blight, but if persistent rain causes the disease to move more than halfway up the plants, they may be doomed. Early blight spreads fastest in humid weather when temperatures are between 80 and 85F (27-29C). ![]() Affected leaves gradually wither to brown and hang on the stems, while leaves higher up on the plant remain green and healthy. The irregularly-shaped spots have concentric rings around their edges, sometimes with a dark dot in the center. The most common cause of dark spots on tomato leaves, early blight begins on the oldest leaves closest to the ground. Worldwide, in temperate climates Description:
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