Late blight is the main disease of tomato in the greenhouse. Early detection, early removal, early control and early cure are all important.
Symptoms: Late blight of tomato can occur from the seedling stage to the end of the season. It damages both the leaves and the stems and fruits. The damage to the leaves and fruits is the heaviest. Generally from the front of the shed to the onset of disease, first invade the leaves and young fruit, and gradually spread to the stems and petioles to make it dark brown, severe plant wilting break. The fruit of the disease was hard and uneven, with a dark greenish oily appearance at the beginning and a dark brown to tan afterwards. In general, the susceptible fruit did not become soft and rot. When the humidity is high, white moulds can be seen at the junction between the front and back of the leaves.
Disease conditions: tomato late blight is a low temperature and high humidity type disease, greenhouse temperature during the day at 22 ~ 24 °C, night at 10 ~ 13 °C, relative humidity of 80% or more can infect plants. In the morning and evening, fog, dew, or drizzle, high humidity, and severe onset. The disease develops quickly. Once it is discovered, it must be prevented and treated as soon as possible.
Prevention:
1. Choose disease-resistant and disease-resistant varieties. Serious disease greenhouses must achieve rotation for more than three years, and can plant non-sweet potato crop rotation.
2. High ridge cover film cultivation; suitable planting density, not too dense, early scaffolding, timely pruning, appropriate removal of the plant's lower leaves, yellow leaves and diseased leaves, improve ventilation and light transmission conditions. The use of formula fertilization techniques, combined use of nitrogen, phosphorus, and potassium fertilizers, increased potash fertilizer can reduce the incidence of disease. Pay attention to reasonable irrigation, avoid flooding irrigation.
3. Each morning, we will finish the draperies, check the leaves and fruits of the tomatoes in the shed, and focus on the 1-2 meters of tomato at the front of the shed to find the central diseased plants. Immediately remove the plants or remove the diseased leaves and diseased fruits. Deeply buried or burned out of the shed to reduce field transmission and control disease occurrence.
4. Temperature and humidity control. The tomato's result period requires the daytime temperature to be maintained at 25-30°C, nighttime at 12-15°C, and minimum temperature not to be less than 10°C. On sunny days, when the room temperature reaches 30°C, the air is released in a timely manner, and when the room temperature is high, the air is released in a short period of time.
5. Scientific medication. Field diseased plants should be removed from the field, and diseased leaves and diseased fruits should be removed. Use 50% Anke manganese zinc WP 500 times, 72% Kelu wettable powder 800X, 72.2% Prokone 800X fluid, or 58 % Rhodamine MnZn WP 500 times spray. The leaves, stems, green fruit, etc. must be sprayed. The middle and lower parts of the plant are the key spray areas and should be used for rotation. Pay attention to the time when fighting drugs must be in the morning. In the afternoon, when the medicine is sprayed, the water does not spread out and the humidity is high, which is detrimental to disease prevention. In case of rainy days, dust or smoke can be used for prevention and control. Dust method: Mu with 5% chlorothalonil dust 1 kg spray powder. Smoke agent method: 45% chlorothalonil smoke agent or 10% fast Ke Ling smoke agent 200 to 250 grams of smoked shed.
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