Prevention and treatment of spinach downy mildew

First, the symptoms

Mainly harmful to the leaves. The lesions were pale green at the beginning, the edges were not obvious, and they were irregular in shape after expansion. The size was different, and the diameter was 3 to 17 mm. When the humidity was high, the gray-white mold layer was formed on the lesions on the back of the leaves, and then grayish purple. The lesion spreads upward from the lower part of the plant. When the drought is dry, the diseased leaves are yellow, and when the humidity is high, the leaves are rotted. The whole plant with heavy disease turns yellow and die, and some of the vegetables are atrophic.

Second, the route of transmission and disease conditions

The pathogens are over-wintered on the host and seeds of the victim or by the oospores in the diseased leaves. The springs produce conidia, spread by airflow, rainwater, agricultural machinery, insects and farming operations, and spores sprout to produce germ tubes. Invaded by the host epidermis or stomata, then sporangia are produced in the affected part and reinfected in the field. Low temperature and high humidity, planting density is too large, water accumulation and early sowing.

Third, prevention and treatment methods

1. The critically ill area should be rotated for 2 to 3 years to strengthen cultivation and management, to achieve appropriate density, scientific irrigation, and reduce field humidity.

2. In the early stage of the disease, spray 80% aluminum triethyl citrate 500 times solution, 64% anti-virus hydrazine powder 500 times solution, 58% metalaxyl manganese zinc 500 times solution, 72.2% phlegm water agent 800 times solution, etc. Spray once a day, continuous control 2 to 3 times, can effectively control the spread of downy mildew. The concentration of the liquid can be appropriately increased when spraying the heavy land, but not excessively to avoid phytotoxicity. At the same time, it can be combined with spraying foliar fertilizer and plant growth regulator for better control. (Xinji City Agricultural Technology Center, Hebei Province)