With the emergence of tomatoes in greenhouses, tomatoes have become vegetables that can be eaten all year round. However, tomatoes in greenhouses are the high incidence of late blight in winter, so be careful. The following small series will introduce you to the prevention and treatment of tomato late blight in greenhouse.
Symptoms
Late blight can harm tomatoes from the seedling stage to the fruiting stage, which can harm the leaves and damage the stems and fruits, and the leaves and fruits are the most seriously damaged. Generally, the disease starts from the front end of the shed, first infects the leaves and young fruit, and gradually spreads to the stalk and petiole, making it dark brown, and when the plant is severe, the plant is wilting and breaking. The fruit of the diseased fruit is hard and the epidermis is uneven. The initial stage is oily and dark green, and then becomes dark brown to tan. When the humidity is high, white mildew can be seen at the border between the front and the back of the leaf.
Causes
The late blight pathogens mainly overwinter on tomatoes grown in winter protected areas and on solanaceous crops, and can also overwinter on sick bodies that fall into the soil. It spreads on tomato plants by air and rain, and directly invades from the pores and epidermis. The temperature difference between day and night in the protected area is large, the temperature is lower than 15 °C, and the humidity is higher than 85%. It is easy to be affected; even cloudy or foggy weather, excessive dense planting, excessive nitrogen fertilizer, flat cultivation, and flooding, the disease occurs seriously.
Prevention
1. Choose varieties that are resistant to disease and disease, and the ward can be used for more than 3 years, and non-chain vegetables can be planted.
2, high ridge cover plastic film cultivation. The density is suitable, not too dense, early scaffolding, timely pruning, appropriate removal of the old leaves, yellow leaves and diseased leaves in the lower part of the plant to improve ventilation and light transmission conditions. Formulated fertilization technology, combined with nitrogen, phosphorus and potassium fertilizers, the application of potassium fertilizer has the effect of reducing the incidence. Pay attention to reasonable irrigation, avoid flooding.
3. After the grass curtain is exposed every morning, check the leaves and fruits of the tomato in the shed, focus on the tomato 1-2 meters in front of the shed, find the central diseased plant, immediately remove the plant or remove the diseased leaves and diseased fruit. Take out the shed or burn it out, reduce the spread of the field, and control the occurrence of diseases.
4, temperature and humidity regulation. The result of the tomato requirement is to keep the temperature at 25-30 °C during the day, 12-15 °C at night, and the lowest temperature at 10 °C. In the deep winter, the temperature must be lower and the straw must be covered. At the same time, the straw should be covered with a film. In the sunny day, when the indoor temperature reaches 30 °C, the air will be released in time, and at low temperature, the air will be released for a short time. Adjust the temperature and humidity in the shed to control the occurrence of the disease.
5. Scientific medication. In the field, the diseased plant should be removed in time, and the diseased leaves and diseased fruits should be removed in time. In the early stage of the disease, 72.2% of the creamy saline solution 800 times solution, 69% of the Mn-Mn-Zn wettable powder 900 times solution or 58% of the toxic manganese can be used. Zinc wettable powder 500 times liquid spray, leaf back, stalk, green fruit, etc. should be sprayed everywhere, the middle and lower parts of the plant are the key spray area, to be rotated. In the case of rainy and snowy days, you can use 45% chlorothalonil or 10% procymidone to smoke 200-250 grams.
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