Systemic products are available, e.g., strobilurins, although they are expensive and, if used too often, the fungus may develop resistance to them. RESISTANT VARIETIES Complete resistance does not exist, but there are varieties which show differences in tolerance to the disease.ĬHEMICAL CONTROL Use protectant fungicides, mancozeb, chlorothalonil or copper products. Avoid planting overlapping crops of tomato, especially if outbreaks of early blight occur.Do not plant one crop of tomato after another in the same land use a rotation of 2-3 years, avoiding crops that belong to the tomato family.Collect plant remains and burn them, or dig them deeply into the soil.Make sure that the plants are healthy by applying fertilizer at recommended rates healthy plants are less susceptible to this disease.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.
#EARLY BLIGHT ON TOMATOES IN NEW AREA FREE#
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. All parts of the plant, leaves, stems and fruit, are infected.
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