Watermelon downy mildew control method

Watermelon downy mildew is easy to occur in the middle and later stage of watermelon plant growth, and the disease mainly harms the leaves. At first, the leaves appear flooded light green spots, then gradually turn yellow, the disease spots continue to expand and change from yellow to light brown, due to the limitation of leaf veins, showing irregular polygonal disease spots, severe disease spots into pieces, leaves curled.

Harmful symptoms of downy mildew in watermelon

Downy mildew mainly harms the leaves, generally starting from the basal leaves, and gradually developing to the upper leaves; at the initial stage of the disease, the leaves first show yellow-green spots, and after the disease spots expand, they show yellow-brown irregular polygonal disease spots limited by the veins, in a humid environment, there is a black mildew layer on the back of the disease spots, and when the disease spots are serious, the whole leaves are yellowish dry and easy to break, and the leaves of the whole field are yellow and yellow, as if they had been roasted by fire. The disease has the characteristics of rapid onset and rapid death.

Incidence regularity of downy mildew in watermelon

In the cold areas of the north, the pathogen can not survive the winter in the open field, the plant dies immediately after withering, and the seeds are free of bacteria. The pathogens in the field are mainly spread by air flow and invade from the stomata of leaves. The occurrence of downy mildew is closely related to the temperature and humidity around the plant. The optimum temperature for the disease is 20-24 ℃. It is easy to invade when there is a water film on the leaf surface. It is easy to occur and develop rapidly when the humidity is high, the temperature is low and the ventilation is poor.

Agricultural prevention of downy mildew of watermelon

The main results are as follows: 1. Watering should be properly controlled in the early stage of the disease, and cultivation in protected areas should pay attention to enhance ventilation and reduce air humidity.

2. Cultivate disease-free and strong seedlings, increase the application of organic base fertilizer, and pay attention to the reasonable combination of nitrogen, phosphorus and potassium fertilizer.

3. Thoroughly remove the fallen leaves of diseased plants after harvest.

Control methods of downy mildew of watermelon

1. Agricultural prevention and control: strict elimination of diseased seedlings when planting. Choose plots with high terrain and good drainage for planting. Apply enough base fertilizer, do not apply too much nitrogen fertilizer during the growing period, in order to improve the disease resistance of the plant. Plant disease is often related to the imbalance of carbon-nitrogen ratio in its body. Strengthening leaf nutrition can improve disease resistance. The solution is prepared according to the ratio of urea: glucose (or sugar): water = 0.5~l:l:100, spraying once every 3-5 days, 4 times continuously, and the control effect is very good.

2. Chemical control

① prevention: Orlick Shuber 50ml, 15kg of water, once every 10 days.

② treatment: Olixabel 50ml + garlic oil 15ml, 15 kg of water, once every 3 days, 2-3 times.