What are the characteristics of downy mildew of Chinese cabbage? How to prevent and cure it?

In the process of planting Chinese cabbage, it is inevitable that some diseases will harm the growth of Chinese cabbage. Downy mildew is one of the important diseases of Chinese cabbage in autumn, which can be harmful in the whole growth period of Chinese cabbage. How to prevent and cure it?

What are the characteristics of downy mildew of Chinese cabbage?

Downy mildew of Chinese cabbage is a common fungal disease during cabbage planting.

When the disease occurs in the cotyledon stage, there is a white mildew layer on the back of the leaf. Under the condition of high temperature, nearly round withered spots often appear in the diseased part. In severe cases, white mildew also occurs on the stem and petiole, and the seedlings and leaves die.

In the adult stage, small green to yellowish spots appeared on the front of the leaves, which were yellowish brown after enlargement, and the disease spots were polygonal when they were limited by the veins of the leaves. When Chinese cabbage entered the pericardium stage, when the conditions were suitable, the disease spots on the leaves increased and connected with pieces, the leaves withered and yellow, and the diseased leaves developed from the outer leaves to the inner leaves.

When the plant is damaged, white mold can grow on leaves, pedicels, flower organs and seed pods, pedicels and flower organs are hypertrophic and deformed, petals are green, seed pods are yellowish, thin and shrivelled.

The disease mainly harms leaves, initially light yellow or yellowish green spots, enlarged and yellowish brown, polygonal or irregular.

Second, how to prevent and cure downy mildew of Chinese cabbage?

1. Select disease-resistant varieties

There were significant differences in disease among varieties. Chinese cabbage varieties resistant to virus disease are generally also resistant to downy mildew and can be selected according to local conditions.

2. Sowing at the right time

The suitable sowing date should be determined according to stubble, variety and climate. Early sowing disease is serious, late sowing disease is mild, but the heart is not enough, but if encountered high temperature and drought years, Chinese cabbage should be properly late sowing, the disease resistance of hybrids is stronger than farm seeds, sowing date can be arranged in advance.

3. Sowing at the right time

The suitable sowing date should be determined according to stubble, variety and climate. Early sowing disease is serious, late sowing disease is mild, but the heart is not enough, but if encountered high temperature and drought years, Chinese cabbage should be properly late sowing, the disease resistance of hybrids is stronger than farm seeds, sowing date can be arranged in advance.

4. Pest control and virus prevention

Early viral disease strains are often early and recurrent strains of downy mildew. Chinese cabbage virus disease is transmitted by aphids. Early prevention and control of aphids should be done. Suitable drugs include 5% acetamiprid EC, 2.5% cyhalothrin wettable powder and 2.5% deltamethrin EC.

5. Remove the central diseased plant and clean the diseased leaves

The central diseased plant can be removed in the early stage of the disease, and the diseased leaves and seriously diseased plants can be cleared out of the field as soon as possible when the disease is common, and do no harm in time.

6. Chemical control

The corresponding prevention and control agents should be selected according to the period of the disease. When there is no disease in the field, if there is continuous rainy, foggy, light and other adverse weather, or field planting is too dense, poor ventilation, 1.6% amine fresh ester water agent or 0.0016% brassinolide water agent can be sprayed to enhance plant disease resistance. At the initial stage of the disease, you can choose 70% Bingsen zinc wettable powder or 75% chlorothalonil wettable powder and other medicine spray protection, once every 5-7 days, continuous prevention and treatment for 2-3 times. During the onset period, 687.5 g / L fluorobacterium ·aldicarb suspension, 45% Dysenamine water agent or 40% triethyl aluminum phosphonate wettable powder can be sprayed once every 7 to 10 days for 2 consecutive times.