What are the control methods for downy mildew in melons?

First, plant varieties with strong disease resistance. Second, do a good job of field management. For example, apply more organic fertilizer, and apply chemical fertilizers with a combination of nitrogen, phosphorus and potassium; after rain in July-August, do not water; if water is needed, water half a furrow; prune the vines in time to maintain ventilation and light penetration. Finally, spray chemicals. At the early stage of disease onset, spray 47% Kasumin wettable powder at 700-800 times dilution and other chemicals, spraying 70 liters of the prepared solution per mu, once every 7-10 days, for 3-4 consecutive sprays.

I. Introduction to melon downy mildew

Melon downy mildew mainly affects cucurbits grown year-round in greenhouses, and can occur continuously. Once it occurs, it usually cannot be controlled, and it spreads extremely quickly. It mainly damages leaves, and is most likely to occur after fruit set at the mature plant stage, when losses are also great.

Melon downy mildew has a wide temperature adaptation, with 15-24°C suitable for its onset; in production, excessive watering or watering followed by moderate to heavy rain, a high groundwater table, and dense plant leaves make it prone to occur; it mostly starts on leaves near the roots, and the pathogen spreads through wind, rain or irrigation water; pathogen germination and invasion have high humidity requirements, and the pathogen can invade only when there are water droplets or a water film on the leaves, with relative humidity above 83% leading to rapid onset.

When infected at the seedling stage, water-soaked small spots appear on the cotyledons, later expanding into light brown lesions, and when humidity is high, a grayish-purple mold layer grows on the underside of the leaves. When mature plants are infected, light yellow lesions appear on the leaf surface and expand along the leaf veins into a polygonal shape. When there is dew or guttation on the leaf surface in the early morning, the lesions appear water-soaked, and later the lesions become light brown or yellow-brown polygonal spots. Under continuous rainfall conditions, the lesions rapidly expand or merge into large patches, causing the leaves to curl upward or dry up, with all the lower leaves drying up, sometimes leaving only a few green leaves near the growing point.

II. What chemicals are used for melon downy mildew?

At the early stage of melon disease onset in July-August, you can spray 47% Kasumin wettable powder at 700-800 times dilution, 60% succinic acid · fosetyl-aluminum wettable powder at 500 times dilution, 70% fosetyl · mancozeb wettable powder at 500 times dilution, 18% metalaxyl · mancozeb wettable powder at 600 times dilution, 64% Sandofan wettable powder at 400-500 times dilution, 72% Kekangling wettable powder at 800 times dilution, 56% Kaoshan water-dispersible microgranules at 800 times dilution, 72.2% Previcur water agent at 600 times dilution, 15% Zhuangyuanle water agent at 200 times dilution, and 15% Xiaomieling water agent at 600 times dilution. Spray 70 liters of the prepared solution per mu, once every 7-10 days, for 3-4 consecutive sprays. If it rains within 4 hours after spraying, re-spray. Stop using the chemicals 3 days before harvest.