Principle and Control of Cauliflower Downy Mildew

Cauliflower is a vegetable, a variety of cabbage, cauliflower is a cruciferous plant, a leaf cauliflower production (20) seed broad, base obtuse, the edge is wavy, smooth glabrous, yellow-and-white flowers of the annual or biennial herbs. Leaves on the root, the main stem and branch stem, the stem is covered with small grains to form a flower, the flower is fleshy, the whole is like a large flower, the color is white and beautiful. Cauliflower is tender, sweet and delicious, and is easy to digest and absorb after eating.

Principle of downy mildew of cauliflower:

Cauliflower downy mildew is common in the north and south of China. The seed collecting plants are mainly harmed in the south, which has a great influence on the seed yield, and when the production field is serious in the north, the yield will be lost to a certain extent. Cauliflower leaves, flower heads, pedicels and pods can all be damaged. The leaf forms the yellow disease spot, the edge is not obvious, has the dark brown stain, the leaf back disease spot has the black brown spot, is more obvious and slightly raised, there is a white mildew layer on the leaf, and when the leaf is serious, the leaf is withered and yellow and falls off. The pedicel is often broken and withered, so that the pods can not bear seeds. The disease produces polygonal spots limited by leaf veins on the back of the leaves, and frost-like mildew is scattered at high temperature. The pathogen of cauliflower downy mildew is flagellum subphylum downy mildew, and its morphology is the same as that of Chinese cabbage downy mildew, but the cauliflower is infected by Brassica varieties of cruciferous downy mildew. The primary infection sources of cauliflower in spring and autumn in northern China came from overwintering and summer mycelia and oospores respectively, while those in southern regions came from pathogens on overwintering cruciferous vegetables. When the average air temperature is 16-20 ℃, the air temperature is high, and the plant surface is covered with water, the disease is easy to occur and epidemic, and the disease is more serious in spring than in autumn in the north, and it is common in winter and spring in the south. When the temperature is low, the damage is more serious. If it is cultivated in the protected area without heating, the disease is serious in winter.

The control methods of downy mildew of cauliflower are as follows:

1. To strengthen cultivation and management, avoid continuous cropping and adjacent cropping with cruciferous vegetables, it is best to rotate with field crops, disease-prone areas or forecast late sowing in rainless years.

2. Select disease-resistant varieties.

3. Seed disinfection, seed dressing with 35% metalaxyl powder with 0.3% seed weight, or 50% Fumei cream, a better effect can be obtained.

4. Chemical prevention, spraying at the initial stage of the disease in the field, commonly used drugs include 40% ethyl phosphate aluminum wettable powder 200 times dilution, or 25% alaxyl wettable powder 700 times dilution, or 75% chlorothalonil wettable powder 500 times dilution, or 70% mancozeb wettable powder 500 times dilution, or 58% mancozeb new 7 wettable powder 500 times dilution.