Tomato leaf spot disease is a newly increased tomato disease in recent years and has become one of the major diseases of tomato in winter and spring.

The disease began in the greenhouse in the county in mid-April this spring. It also occurred in tomatoes in the small greenhouse. At the beginning of the onset, there was a central diseased plant, and then spread from the central diseased plant to the surrounding area until the entire shed occurred. The incidence of individual plants is often spread upward from the lower leaves. The pathogenic bacteria can overwinter in the soil in the body or the seed, and the temperature and humidity in the next year are suitable to produce conidia, and the initial infection and reinfection can be carried out through wind and rain. Warm and humid, long days of cloudy rain and condensation are important conditions for the onset of illness.

Harmful symptoms:

The disease can appear on both young and old leaves. In the early stage of disease, the leaf surface was full of round or irregular spots. The center of the lesion was light brown and surrounded by dark brown. The color of the leaves on the back was darker than the front of the leaves, and was dark brown in the surrounding. The lesions are slightly concave, more small, and also have larger round brown lesions. The lesions expand over time and are irregularly shaped by veins. The lesions were thin and later easily broken and perforated. Leaf margins can also be affected, with irregular lesions along the leaf margins, and the leaves are almost identical in color on the front and back. Lesions often develop along the leaf margins, forming lamellae, dark brown, and with the leaves drying, the spots gradually fade from gray to gray-brown. When the damage is severe, all the leaves turn yellow. The infested leaves gradually turn brown and soon die and fall off from the plants. Symptoms of leaf spot disease are basically limited to the leaves, but also occur at the stem and petiole areas when environmental conditions are appropriate.

Incidence rule:

Germs can lurk in the soil or on the seeds with the sick. When the temperature and humidity are appropriate, conidia are produced for initial infection. Warm and humid rainy days and long duration of condensation are important conditions for the onset of disease. General soil fertility is insufficient, plant growth is debilitating or nitrogen fertilizer is too much, and the disease is severe when the plants are long.

Control methods:

An agricultural measure

1, choose resistant varieties.

2, strengthen management. Increase organic fertilizer and phosphorus and potassium fertilizers. Spray foliar fertilizers to enhance plant resistance to disease.

3. Eradicate the source of infestation, remove the diseased body after harvest, and focus on incineration.

Second, chemical control

1. In case of no disease or early stage of disease, use 65% zein-zinc (blue) wettable powder or 40% chlorothalonil (sayan) suspension 500 times spray. Use it once more every other week.

2. After the onset of illness, use 25% Difenoconazole plus 25% Propiconazole (Exhibition) EC 1500 times, or 15% Difenoconazole plus 15% Propiconazole (Birun) EC 1000 times treatment

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