Detailed Explanation of Key Technical Points for Controlling Grape Powdery Mildew
Grape powdery mildew is a difficult-to-control fungal disease that has occurred widely in recent years. Both table grapes and wine grapes are susceptible to it, and it most easily affects the young and tender organs of grapevines, such as leaves, new shoots and fruit. In particular, as the area planted with table grapes continues to increase, the damage is especially severe in Shandong, Hebei and the northern foothills of the Qinling Mountains in Shaanxi, north of the Yellow River. It not only reduces grape quality and yield, but also affects the appearance and taste of the grapes. So what is the control technology for grape powdery mildew?
1. Clean the vineyard at the right time
After harvesting in autumn, clean the vineyard promptly, thoroughly remove fallen leaves, diseased branches and diseased fruit from the orchard, and spray lime sulfur mixture; during the disease season in the growing period, promptly remove diseased leaves and diseased fruit, take them out of the orchard and destroy them promptly; in spring, when the grapevine sap begins to flow, spray lime sulfur mixture; during the disease season in the growing period, promptly remove diseased leaves, diseased fruit, diseased shoots, etc.
2. Strengthen cultivation management
Apply more organic fertilizer in the field, appropriately increase the application of phosphorus and potassium fertilizers, strictly control the use of nitrogen fertilizer, and improve the disease resistance of the vines; make scientific use of pruning techniques, and prevent powdery mildew in a timely manner during the growing period.
3. Use chemical control scientifically
Before the grape buds swell but have not yet sprouted, spray 3~5°Be lime sulfur mixture or 45% crystalline lime sulfur mixture at 40~50 times dilution 2~3 times for prevention, which can effectively control the initial infection and reduce later disease development.
In addition, under high temperature and high humidity conditions in June, in combination with the above management measures, promptly spray once with chlorothalonil or carbendazim at 1000 times dilution after the rain clears, to prevent the occurrence of grape powdery mildew and other diseases. If grape powdery mildew is found, promptly spray triadimefon at 800~1000 times dilution, and spray again after an interval of 7~10 days, or apply 0.3% tetramycin 50g + water 70kg for control, and spraying 2~3 times continuously has a significant effect.
Sulfur preparations are the basic agents for controlling grape powdery mildew, including lime sulfur mixture, sulfur powder, sulfur suspension concentrate, etc., all of which have good therapeutic effects on grape powdery mildew. Be sure to persist in spraying protective fungicides. These agents are used at the key periods before and after flowering and have the advantage of a long duration of effect. They can also be used in combination with therapeutic agents after plants develop the disease. Generally, protective fungicides include chlorothalonil, agricultural antibiotic 120, wuyiencin, etc. The number of applications depends on the specific situation, and the general interval is 1 spray every 7~10 days.
Precautions: Strictly use the above pesticides and concentrations. Stop spraying triadimefon 20 days before grape harvest, stop spraying carbendazim and chlorothalonil 10 days before harvest, and stop using any pesticide 7 days before harvest. When spraying, spray the leaf surfaces and fruit clusters evenly at the same time.
4. Strengthen fertilizer management
In combination with irrigation, apply 200~300g of a mixture of triple superphosphate and diammonium phosphate to each grapevine, and do not apply urea. When fertilizing, keep 30~40cm away from the grapevine, bury to a depth of 10~20cm, and water immediately. Spraying potassium dihydrogen phosphate foliar fertilizer allows nutrients to be quickly absorbed by the vines, improving fertilizer use efficiency and the nutritional level of the vines. It reduces dried cluster tips and dried fruit tips in grapes, increases the sugar content and coloring of the grapes, and enables the grapes to mature earlier.