Lettuce planting: what is lettuce downy mildew?

What is lettuce downy mildew? What harm does downy mildew do to lettuce? What prevention and cure method does lettuce downy mildew have? Hope that experienced netizens can help guide the harm and control methods of lettuce downy mildew, the following is a detailed introduction for reference: lettuce downy mildew harm: lettuce seedlings and adult plants can be harmed by downy mildew, so that adult plants can be seriously harmed, mainly harmful to leaves. The diseased leaves spread upward from the lower part of the plant, and at first there was a light yellow near-circular polygonal spot on the leaf. When it was wet, the disease spot on the back of the leaf grew white mold, that is, the cyst peduncle and sporangium of the pathogen, and sometimes spread to the front of the leaf. In the later stage, the disease spot withered into yellowish brown and connected into pieces, causing the whole leaf to dry up. In the overcast and rainy late spring or autumn, the disease is serious; planting is too dense, too much watering after planting, soil moisture or poor drainage is easy to occur. Lettuce downy mildew control methods: 1. Select disease-resistant varieties: general root, stem, leaf with purplish red or dark green varieties are more resistant. 2. 2. Disease-free seeds were selected and rotation was carried out for 2-3 years. 3. Strengthen cultivation management, reasonable close planting and plastic film mulching: if plastic film mulching is not adopted, the times of intertillage should be increased, the field humidity should be reduced, and field drainage should be done well to prevent stagnant water. 4. Chemical prevention and treatment: the control effect can be improved by concentrated spraying in the seedling bed and transplanting with medicine before planting at the seedling stage. The field should start spraying at the initial stage of the disease, and the medicine should be sprayed on the back of the leaves, once every 5-7 days, 2 times in a row. Pay attention to the rotation of medication and stop using it more than 15 days before harvest. Click for more lettuce planting techniques click to get more vegetable planting techniques