Grape powdery mildew can infiltrate all green parts such as leaves, fruits, and vines, and young tissues are more susceptible to infection and harm. Leaves suffer damage, irregular shaped faded green or yellow patches on the front of leaves, visible on both sides of the lesions covered with a layer of white powder (usually more on the front, less on the back), and when the powder is full Leaf, uneven foliage, gradually curling and wilting; fresh shoots, fruit stems and cobs affected, irregular brown or dark brown spots, feathery lines extending outwards, covered with white powder, make the spike Axes and fruit stems became brittle and shoot growth was blocked.
Grape powdery mildew usually begins from late May to early June, and is in full bloom from mid-to-late June to late July. Planting and cultivation of grapes are most susceptible to the occurrence and prevalence of powdery mildew; grape growing areas with arid growing season are conducive to the occurrence of powdery mildew; for grape growing areas such as rainwater, there is a high chance of occurrence of powdery mildew in drought years; Powdery mildew is not easy to occur in epidemic regions where there is much seasonal rain, and if the plants are cultivated too densely, excessive nitrogen fertilizer is applied, pruning and picking of the shoots are not timely, and the branches and shoots are too long, and the air or light is in poor condition, the plant skin is fragile and the disease is severe. . In addition, young shoots, young leaves, and young fruit are susceptible to disease.
The key points in preventing powdery mildew:
1. Do a good job of field sanitation, clean out branches, leaves, diseased grains, diseased stems, and cobs from the field and concentrate the treatment (high-temperature fermentation compost, high-temperature treatment, etc.);
2. Spray lime sulfur before germination;
3. After the fall of flowers, it is a critical period for the control of powdery mildew;
4. The young fruit growth period to the color change period must be strictly monitored and the disease should be found and handled in time.
Powdery mildew prevention agent:
1. Sulfur preparations include lime sulfur, sulfur powder, sulfur rubber suspension, etc. It has a good therapeutic effect on grape powdery mildew, and it is the basic medicine for controlling grape powdery mildew.
2. The protective bactericide is used in the critical period before and after flowering to exert its broad spectrum and long duration, and it can also be used in conjunction with therapeutic agents after onset. Chlorothalonil, NPK 120, Wuyimycin, Bacillus preparations, etc.;
3 within the suction fungicide Difenoguanidine, tebuconazole, azoxystrobin.
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