Heavy occurrence of grape downy mildew caused by foggy and continuous rainy weather: how to prevent and control it?
The main disease during the grape growing period includes downy mildew. The occurrence and epidemic of downy mildew are closely related to climatic conditions, and it is most likely to occur in late spring and early summer or autumn when there is a lot of fog, heavy dew, or continuous rainy weather. At the same time, low-lying vineyards, overly dense plants, branches and leaves, and too-low trellises with poor ventilation and light transmission can also easily lead to this disease. Grape downy mildew spreads quickly and damages grape leaves, causing leaves to dry up and fall off, resulting in severe yield reduction of 20-40%, or even total crop failure. The prevention and control techniques for grape downy mildew are as follows:
Grape downy mildew
1. Remove the source of the disease. In autumn, clean the vineyard, remove diseased branches and leaves, and carry out deep soil plowing.
2. Apply fertilizer scientifically and strengthen management. During the grape growing period, avoid partial application of nitrogen fertilizer, increase the application of phosphorus and potassium fertilizers and decomposed organic fertilizer to improve disease resistance; prune in time and prune reasonably to prevent branches, vines, and leaves from being too dense; appropriately strengthen ventilation and light transmission in the vineyard to reduce humidity inside the vineyard; irrigate at the right time and in the right amount, and pay attention to drainage after rain to reduce ground humidity and reduce opportunities for pathogen infection.
3. Chemical control. Before the disease occurs, spray 1:0.5-0.7:200 Bordeaux mixture for prevention. Seize the key period before pathogen infection to spray the first application, then spray once every half month, 3-4 times in total, for a good preventive effect; after the disease occurs. Spray 65% zineb wettable powder 500 times solution or 40% phosethyl-Al wettable powder 300 times solution in time, once every 7-10 days, spraying 2-3 times in succession, for a good therapeutic effect on grape downy mildew.