Grape powdery mildew control and ** strategy.
In China, powdery mildew is widespread in wine-growing areas. Although rain has a detrimental effect on the occurrence of powdery mildew, the incidence and prevalence of powdery mildew is relatively low in areas with high rainfall during the growing season. In arid areas such as Xinjiang, Gansu, Ningxia and northern Hebei, powdery mildew is more common and harmful due to less rainfall. Rain-sheltered cultivation, facility cultivation and dry grape growing areas during the growing season are all conducive to the occurrence and prevalence of powdery mildew.
Site and symptoms of infection.
Powdery mildew can infect all green parts of grapes, including leaves, branches and fruits. Tender tissues are more susceptible to damage and appear as grayish-white, "oily" lesions with indistinct edges. In severe cases, the back of the leaf will also be covered with a grayish-white powder, causing the leaf to shrink, wilt, and eventually fall off. Cobs, stalks, and shoots may also be affected, with irregular brown or black-brown spots covered with white powder. The damaged inflorescence shafts, cob shafts, and fruit stalks will become fragile and easy to break, while the branches will not mature properly.
Young fruits or fruits with a sugar content of less than 8% are particularly susceptible to powdery mildew. When these fruits are infected, a grayish-white powdery mold layer appears on the surface and may have brown or purple-brown reticulations underneath. After the small and young fruits are damaged, the fruits are not easy to grow and fall easily; Large and young fruits may become hard, deformed, and longitudinally dehiscible; Disease in the veraison stage will make it difficult to accumulate sugar, and the taste will be sour and easy to crack.
Prevention and control strategies. Timely cleaning of diseased tissues is the basic measure for the prevention and treatment of powdery mildew. Before and after flowering, the use of pesticides in combination with the control of other pests and diseases can effectively control the number of powdery mildew epidemic bacteria. In addition, the fruit development period also needs to be strictly monitored, and once signs of powdery mildew are found, corresponding measures should be taken immediately to deal with them.
Sulfur preparations such as stone sulfur mixture, sulfur powder or water dispersible granules have a good effect on grape powdery mildew. 50% Fumei double wettable powder is also a commonly used protective biocide. Other systemic fungicides such as 25% hexaconazole suspension and 24% benzolate, pyrazole suspension can also be used**. The application of 10% difenoconazole water-dispersible granules at the young fruit stage after flowering can treat grape anthracnose and white rot at the same time, which is safe for young fruits, and normal use will not inhibit growth.