Control methods of watermelon powdery mildew

Powdery mildew is a common disease of watermelons, which is distributed in all watermelon producing areas throughout the country. spring watermelons and autumn watermelons can occur in the south, but autumn watermelons occur more seriously in autumn, and watermelons in open fields in the north occur in summer. protected areas such as greenhouses and plastic greenhouses can be infected throughout the growth period, but they are serious in the middle and later stages of growth. let's take a look at the prevention and control methods of watermelon powdery mildew.

Damaging symptoms

Watermelon powdery mildew mainly harms leaves, followed by petioles and stems, and generally does not harm fruits. In the early stage of the disease, white nearly round star-shaped powder spots were produced on the leaf surface or on the back of the leaf, and most of them were on the leaf surface. when the environmental conditions were suitable, the powder spots expanded rapidly and connected into a large powder area with no obvious edge, which was covered with white powder mold. in severe cases, the whole leaf surface is covered with white powder. There is less white powder on petioles and stems. The disease gradually spread from old leaves to new leaves. In the later stage of the disease, the white mold layer turned gray due to the maturity of the hyphae, and the diseased leaves were withered and yellow, curled and generally did not fall off. When the environmental conditions are not conducive to the reproduction of the bacteria or the senescence of the host, piles of yellowish-brown particles appear on the disease spot, and then turn black.

Occurrence condition

The occurrence and prevalence of watermelon powdery mildew are closely related to temperature, humidity and cultivation management. the watermelon fields with too much nitrogen fertilizer, overgrowing plants, lack of soil water and untimely irrigation are easy to occur. the disease is also serious in watermelon fields with too much irrigation, increased humidity, low-lying terrain, poor drainage or close to protected areas such as greenhouse. The resistance of watermelon to powdery mildew is also different in different growth stages, and the disease resistance of young leaves in seedling stage or adult stage is generally strong.

Prevention and cure method

The main results are as follows: 1. Reasonable close planting and high border and deep trench planting mode, covering the border with plastic film, focusing on strengthening field management after melon period, reasonable pruning, timely removal of diseased heavy leaves and some old leaves, so as to facilitate ventilation and light, reduce field humidity and reduce repeated infection of bacteria.

2. Grasp the characteristics of watermelon loving water and afraid of water, adopt dry-wet irrigation method, pay attention to drainage after rain, prevent melon field from being soaked and waterlogged, and apply medicine after continuous rainfall to prevent the disease from spreading rapidly in melon field.

3. To do a good job of fertilization, mainly organic fertilizer, the combination of organic fertilizer and inorganic fertilizer, nitrogen, phosphorus and potassium combined application. Compound fertilizer should be the main topdressing in the later stage of watermelon, with little or no urea application as far as possible, so as to improve the disease resistance of the plant.

4. Strengthen the cultivation management and pay attention to the combined application of nitrogen, phosphorus and potassium fertilizer to prevent the partial application of nitrogen fertilizer. Cultivate healthy plants. Pay attention to timely plant adjustment to prevent leaf vines from being too dense and affecting ventilation and light transmission. Cut off the diseased leaves and burn them in time to prevent spread.

5. The key point of chemical control of watermelon powdery mildew is to do a good job in the early stage of the disease, such as the disease continues to develop after application. When spraying, the amount of water should be sufficient, the back of the leaves should be sprayed, and the whole field should be sprayed evenly to prevent leakage.