Make sure that these are disease-free and not taken from plants that were previously infested by the early blight disease. Proper selection of seeds and tubers for sowing/planting.Too much moisture during cool and warm weather.Over crowded plants that cause the poor flow of air among the plants.Infested tomato seeds and potato tubers.Examination of internal damage shows a brown to black corky, dry rot, usually not more than 1/4 to 3/8 inch deep and deeper cracks may form in older lesions. There is usually a well-defined and sometimes slightly raised margin between healthy and diseased The lesions are usually slightly sunken, circular or irregular, and vary in size up to 1.8 cm (3/4 inch) in diameter. Infected fruits often drop before reaching maturity.Īn Infested potato tuber has surface lesions that appear a little darker than the adjacent healthy skin. Fruits can also be infected during the green or ripe stage through growth cracks and other wounds. Affected areas may be covered with velvety black masses of spores. These spots may enlarge to involve the entire upper portion of the fruit, often showing concentric markings like those on leaves. The fruit stems are spotted with lesions that lead to loss of the young fruits.Īn infested tomato fruit has dark, leathery sunken spots, usually at the point of the stem attachment. Infestation during the flowering stage of tomato causes the blossoms to drop. Concentric markings, similar to those on leaves, often develop on Early blight lesions show a generally dry "bulls-eye" angular pattern that do not usually spread very far and rarely affect petiole tissue, as the progress of the fungus is stopped by the veins of the leaf.Īn infected stem has small, dark, slightly sunken areas that enlarge to form circular or elongated spots with lighter-colored centers. Infected leaves eventually wilt, die, and fall off. Infection usually begins on the lower, older leaves and progresses up the plant. Dark, concentric circles (circles with a common center) are found within these lesions.
The infected leaf has circular lesions of about 1.2 cm (1/2 inch) in diameter. Collar rot occurs when the young stem becomes girdled with dark lesions at the soil level. Seedlings grown from infested seeds may damp off soon after emergence because large lesions develop at the ground line on stems of transplants or seedlings.
Photo courtesy of University of MinnesotaĮarly blight produces a wide range of symptoms at all growth stages of both potato and tomato which include damping-off, collar rot, stem cankers, leaf blight, and fruit/ The most important hosts are tomato and potato but it will also attack eggplant, pepper, horse nettle, black nightshade, wild cabbage, cucumber, and zinnia.
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