The latest control methods of watermelon leaf blight

Leaf blight is one of the common diseases of watermelon, which is more common than that on open-field watermelons in summer and autumn, and watermelons can also occur in spring. The incidence rate is 1030%, and the plant rate of serious land disease is more than 80%. It withered a large number of leaves and significantly affected watermelon production. In addition to harming watermelon, it also harms melons, cucumbers, wax gourds, pumpkins and other cucurbitaceae plants. Let's take a look at the prevention and control methods of watermelon leaf blight.

Hazard characteristics

Watermelon leaf blight mainly harms leaves, but also harms vines and fruits. Cotyledons of seedlings often occur at the edge of leaves, first as small spots, and then expand into brown, round or semicircular spots, which can harm the whole cotyledons and wither them under high humidity conditions. True leaf damage, mostly occurred in the leaf margin or between the veins, at the beginning of the small spots, in high humidity rapid merger, infiltration, so that the leaf dehydrated and withered. In high temperature and dry weather, round brown spots with a diameter of 2 to 3 mm are formed. when the weather is wet, they can be merged into large brown spots, which become thinner and cause leaf withering in severe cases. The stem vine is damaged, resulting in oval or fusiform, slightly sunken light brown spots. When the fruit is damaged, it produces round sunken dark brown spots that are slightly raised around it, and when serious, it causes the fruit to rot.

Occurrence regularity

The pathogen of watermelon leaf blight is not strict on temperature, the temperature is 14-36 ℃ and the relative humidity is higher than 80%. It is easy to spread or occur when the relative humidity is higher than 90%. Wind and rain is conducive to the spread of the pathogen, causing the disease to occur generally, continuous cropping land, partial or heavy application of nitrogen fertilizer and barren soil, weak plant disease resistance and serious disease. Continuous sunny days and long sunshine have an inhibitory effect on the disease. There were differences in disease resistance among varieties, and Admiralty and Guannong were more susceptible. In recent years, it is becoming more and more serious, which should be paid attention to in production.

Prevention and cure method

1. Establish disease-free field and select disease-tolerant varieties suitable for local cultivation. At present, the more disease-resistant varieties are Zhengzhou 5, Zhengza 7, Xinnong 8, Yueyou 2, Fuzhou watermelon, Xinhongbao and so on.

2. After the watermelon is harvested, pay attention to remove the diseased remains, concentrate on burying or burning them, and do not pile up the diseased bodies at the edge of the field.

3. Adopt formula fertilization technology, apply compost made by enzyme bacteria retting, avoid excessive application of nitrogen fertilizer, and start spraying Huimanfeng liquid fertilizer before sitting melon, 320ml per mu to 500 times of water to improve disease resistance.

4. To determine the sowing date scientifically, the open field should sow seeds when the daily average temperature is more than 15 ℃ and the soil temperature at the depth of 5 cm is more than 12 ℃. If you want to get early, you can use plastic film mulching to reach the above temperature before sowing.

5. Soak the seeds with 75% chlorothalonil wettable powder or 1000 times of 50% prohydantoin wettable powder for 2 hours, rinse and then accelerate germination and sow seeds.

6. the cultivation method of rain shelter should be advocated conditionally, and watermelons in the open field should pay special attention to trenching and drainage after rain, so as to prevent moisture retention, which plays an important role in alleviating the disease.

7. Using the method of frame cultivation, 1500 plants per mu, single vine pruning, picking the first female flower at 6-7 leaves, retaining 12-13 leaves, not only increase yield and income, but also reduce the disease.

8. It is effective to spray 1500 times of 50% Sukeling wettable powder or 1000 times of 50% prohydantoin wettable powder, 75% chlorothalonil wettable powder, 70% mancozeb wettable powder or dry suspension powder and 80% Dasheng wettable powder when there is no disease spot before the disease. 60 liters of good solution per mu, once every 7 days, 3 times in a row.