What is downy mildew in lettuce cultivation?
What is lettuce downy mildew? What harm does downy mildew do to lettuce? What control methods are there for lettuce downy mildew? I hope experienced readers can help advise on the harm and control methods of lettuce downy mildew. The following is a detailed introduction for reference: Harm of lettuce downy mildew: Lettuce seedlings and mature plants can both be affected...
What is lettuce downy mildew? What harm does downy mildew do to lettuce? What control methods are there for lettuce downy mildew? I hope experienced readers can help adviseThe harm and control methods of lettuce downy mildew are introduced in detail below for reference:
Harm of lettuce downy mildew:
Lettuce seedlings and mature plants can both be harmed by downy mildew, with mature plants suffering more severely, mainly on the leaves.
Diseased leaves spread from the lower part of the plant upward. At first, pale yellow nearly round to polygonal spots appear on the leaves. When humid, white mold, namely the pathogen's sporangiophores and sporangia, grows on the spots on the underside of the leaves, sometimes spreading to the upper surface of the leaves. Later the spots die and turn yellow-brown and join together, causing the entire leaf to dry up.
The disease is severe in late spring or autumn with continuous rain; planting too densely, watering too much after transplanting, moist soil or poor drainage makes the disease more likely.
Control methods for lettuce downy mildew:
1. Choose disease-resistant varieties:Generally, varieties with purple-red or dark green roots, stems and leaves are more resistant to the disease.
2. Use disease-free seeds and practice 2-3 year crop rotation.
3. Strengthen cultivation management, plant at a reasonable density, and use plastic film mulching:
Where plastic film mulching is not used, increase the number of cultivations to reduce field humidity; ensure good field drainage to prevent waterlogging.
4. Chemical control method:
Seize the period before transplanting at the seedling stage, spray the seedlings concentratedly in the seedbed, and transplant with the pesticide so as to improve the control effect. In the field, spraying should begin at the early stage of the disease. The pesticide must be sprayed onto the underside of the leaves, once every 5-7 days, for 2-3 consecutive sprays. Note to rotate the pesticides and stop using them at least 15 days before harvest.
Click to get more lettuce cultivation techniques
Click to get more vegetable cultivation techniques