Vulnerable plants should be pruned or staked to improve air circulation, and promote a rapid drying of the leaves.Infected fruit and leaves may be prematurely shed from the plant. Fruit lesions generally appear close to the stem. Lesions that develop on infected fruit are leathery and black, with raised concentric ridges. If the infection girdles the stem, the seedling will wilt and die. The stem proceeds to rot, turning brown, and assuming a dry, sunken appearance. On seedlings, stems are infected at or just below the soil surface. When plants are defoliated, sunscald may occur. Severely infected plants will be rapidly defoliated. As the infection advances, the leaf spots spread outward, causing the affected plant to turn yellow, wither, and expire. High temperatures, and wet humid conditions are conducive to the spread of early blight.Įarly blight symptoms initially appear on older leaves as small, brown spots, with dark brown concentric rings. Early blight infections can occur throughout the growing season. Plants can be infected at any stage of their development. Once a plant has been infected, it will form leaf spots within five to ten days. The lower leaves of susceptible plants can be infected when they make direct contact with diseased soil. Early blight may also be transmitted via contaminated tomato seeds, transplants, or potato tubers. In spring, once temperatures have risen and conditions are sufficiently moist, infectious spores are spread to vulnerable plants by splashes of rain, air currents, insect vectors, and pruning equipment. Early blight is especially severe on plants that have been weakened by environmental stressors, or insect infestations.Įarly blight overwinters on infected plant debris, and in diseased soil. Eggplants may also be infected, as well as several weeds and ornamental plants in the Solanaceae family, including black nightshade and hairy nightshade. Early blight infections affect entire plants, resulting in defoliation, and often, plant mortality.Įarly blight occurs throughout the United States, wherever susceptible plants are present.Įarly blight primarily infects potato and tomato plants. solani infects potato plants more often than A. tomatophilia is more virulent on tomato plants than A. tomatophilia is present in an area, it is the primary cause of early blight on tomato. It is caused by two closely related fungi: Alternaria solani and Alternaria tomatophilia. Early blight is a serious fungal disease that afflicts tomato and potato plants.
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