Control method of melon downy mildew

Muskmelon downy mildew is a kind of fungal disease aimed at muskmelon outbreak, which is mainly aimed at planting melons in greenhouse all year round, which can occur continuously. Once it happens, it is usually out of control, and the epidemic is very fast, causing the middle and lower leaves to dry up very quickly, and the loss is also great. It can be controlled through field management or chemical spraying. Let's take a look at the prevention and control methods of muskmelon downy mildew.

Harmful symptoms

Muskmelon downy mildew is mainly harmful to leaves. When infected at the seedling stage, water-stained spots appeared on the cotyledons, then expanded into light brown spots, and a grayish-purple mildew layer grew on the back of the leaves when the humidity was high. When the adult plant is infected, the light yellow disease spot appears on the leaf surface, which expands in a polygonal shape along the leaf vein. When there is condensation or spitting water on the leaf surface in the early morning, the disease spot is flooded, and in the later stage, the disease spot becomes light brown or yellowish brown polygonal spot. Under the condition of continuous rainfall, the disease spot rapidly expanded or fused into large patches, causing the leaves to roll up or dry up, and all the lower leaves dried up, sometimes leaving only a few green leaves near the growing point. During the fruit development period, the disease spread rapidly during the rainy season, and the yield was reduced by 3050%.

Disease condition

The pathogen of muskmelon downy mildew had a wide adaptability to temperature, and 15-24 ℃ was suitable for its occurrence. It is easy to suffer from excessive watering or moderate to heavy rain, high groundwater level and dense leaves after watering. Most of them start from the leaves near the roots, and the bacteria are spread by wind, rain or irrigation water. Bacteria germination and invasion require high humidity conditions. Only when the leaves have water droplets or water film can the bacteria invade, and the disease occurs rapidly when the relative humidity is higher than 83%.

Prevention and cure method

1. Agricultural control: select varieties with resistance to downy mildew, such as Yellow River melon, red meat reticulated melon, Snow White, Suizhou white melon and so on. Implement crop rotation, timely drainage after rain, do not flood irrigation. Apply fertilizer reasonably, trim the vine in time, keep ventilated and transparent. Avoid neighboring or continuous cropping with melons and adopt rain shelter cultivation under certain conditions. It is not suitable to be watered after the rain from July to August. If water is needed, half of the ditch should be watered, and flood irrigation should be avoided.

2.Nutrition control: after flowering, 0.2kg urea and 0.5kg white sugar (or brown sugar) per mu were sprayed on the leaves of 40-50kg water, once every 5-6 days, even 5 times, or 50-70kg per mu of organic active liquid fertilizer such as "Gaomeishi UA-102 nutrients" was sprayed on the foliar and root soil, once every 10 days, twice in a row to enhance plant resistance and prevent disease.

3. Chemical control: spraying 70% ethyl phosphorus ·manganese zinc wettable powder 500 times, or 18% metalaxamide ·manganese zinc wettable powder 600 times, or 64% germicidal alum wettable powder 400 times 500 times, or 72% Kangling wettable powder 800 times, or 50% Fumishuang wettable powder 600 times, or 25% Ruidui wettable powder 800 times, or 20% benzaxyl EC 350 times. Or 72% Kelou wettable powder 700 times solution, once every 7 to 10 days, continuous prevention and treatment for 3 times.