12/13/2023 0 Comments Blight treatment for tomatoes![]() Control weeds, as these may be sources of the fungus, especially those in the tomato/potato family.Preferably, water only at the base of the plant avoid overhead irrigation or, if used, apply early in the day, to make sure the plants are dry before nightfall.Prune any diseased leaves from the bottom of the plants as they become infected.Remove a few branches from the lower part of the plants to allow better airflow at the base. ![]() Space plants (60-90 cm) so that air circulates around them this helps to dry the leaves rapidly after overhead irrigation or rain.Select fields with good drainage, and where surrounding trees do not prevent airflow, so that leaves dry as rapidly as possible after rain or overhead irrigation.If symptoms are seen, discard the plant, and spray with fungicide. Carefully check each seedling before transplanting in the field, and remove any that show early blight symptoms.Remove any 'volunteer' tomato plants as well as weeds, especially those in the tomato family, from around nurseries, and in and around field plots.Make sure that the seed is free from contamination of the fungus, by saving seed only from disease-free plants.Favourable conditions for the disease are warm, humid weather with heavy dews or rains. Survival occurs in crop remains, and also on seed. Spread over short distances occurs when spores are moved plant-to-plant in wind, rain and overhead irrigation water. Spots also occur on the stems of seedlings as large brown spots near soil level, and may lead to stem break and death. The rots become covered in black spore masses of the fungus (Photo 5). On the fruits, the spots are dark brown or black, sunken, extending over part or all of the fruit. On the stems, the spots are similar, except that they are darker and more elongated (Photo 4). Loss of leaves can cause sunscald on the fruits. As they grow, they develop dark brown rings, like a target, a characteristic of the disease (Photos 1&2, tomato & Photo 3, potato). The spots often merge, and the leaves dry up and fall. Small, pinpoint to 6 mm, circular to angular brown spots occur on the older leaves, with yellow margins. FL DPI Archive, FDACS, Bugwood.All parts of the plant, leaves, stems and fruit, are infected. Lesions on tomato leaves and stems ( Lycopersicon) caused by late blight. Lesion on tomato leaf ( Lycopersicon) caused by late blight. For an organic approach to Strategy 5, consult the Organic Materials Review Institute (OMRI™) for appropriate organic copper products. Strategies 1, 2, 3, and 4 are strictly organic approaches. Apply when symptoms are first identified. Do not plant tomatoes, potatoes, and celery in succession. Remove and destroy any affected plants as soon as they are observed.Ĥ. Both of these practices can spread the fungal spores from plant to plant.ģ. Avoid working around plants when they are wet. Several tomato varieties are designated as resistant to late blight.Ģ. Infection rarely occurs when temperatures are higher than 80 degrees F and humidity is less than 90%.ġ. The fungus invades the plant through leaf stomata. The spores are transmitted by water or are wind blown and may be introduced from diseased plants in nearby gardens. The fungus can produce spores over a broad range of temperatures although spores are most infective at temperatures of 68 degrees F with high humidity. The fungus overwinters on tomato and potato plant debris, including potato tubers. On the fruit, you will see rough, firm, dark-colored spots. These patches will enlarge quickly, and in moist weather, a downy growth may develop on the underside of the leaf. Green-black watery patches develop on the upper surfaces of older leaves. Late blight attacks the older leaves first, then spreads to the fruit. One of the first symptoms of late blight is watersoaked patches on older leaves. Watch for the disease when cool, moist nights are followed by warm, humid days. Late blight is more common in north central and northeastern states, but is observed in the Midwest when the humidity is high and temperatures are around 68 degrees F late in the growing season. As the common name implies, Phytophthora is prevalent on tomato hosts in late summer, after the plants have bloomed. Late blight on tomato fruit ( Lycopersicon)Ī strain of the fungus, Phytophthora infestans, causes late blight in tomatoes.
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