Grape downy mildew is one of the most harmful grape leaf diseases. When the disease is severe, the diseased leaf scorches and settles early. In that year, it can reduce production by 10% to 20%, and make the yield in the second year significantly affected. First, symptoms of grape downy mildew mainly damage the leaves, but also can infect new young fruit and other young tissues. The leaves were damaged, and the spots with unclear edges of the primary yellowish water spots were gradually enlarged to brown irregular spots or polygonal spots, and the spots were connected to become irregular spots. When the weather is wet, white frosty fungal cysts and sporangia are produced on the back of the lesion. When the onset is severe, the diseased leaves will soon fall off and fall early. The young shoots become victimized, resulting in water-stained spots, followed by brown spots that are slightly sunken, and lesions that produce white downy mildew. When the disease is heavy, new shoots are twisted, growth stops, and even death occurs. Tendril, cobs, and petioles can sometimes be harmed, and their symptoms are similar to those of young shoots. The young fruit was killed, the disease department faded, and the body became hard and subsidence. White downy mildew was produced and it was easy to shrink and fall off. When the fruit is half dead, the diseased part is brown to dark and the soft rot falls off early. After the fruit is colored, it is no longer infested. Second, the occurrence of regular pathogens for grape downy mildew, is a flagellin subphylum, oomycete Myzus persica, Plasmodium. The grape downy mildew bacteria overwinter in the diseased tissue with oospore, or overwinter as the diseased leaves remain in the soil. In the following year, the oocysts germinate under appropriate conditions to produce sporangia, which then produce zoospores, spread by wind and rain, and invade from the dorsal stomata for initial infection. After 7-12 days of incubation, sporangia and sporangia are produced in the diseased area. The spores germinate and produce zoospores to infect again. The suitable temperature for sporangia germination is 10°C-15°C. The suitable temperature for zoospore germination is 18°C-24°C. In autumn, it is cold, rainy and dew, and it is easy to cause disease epidemics. Orchard low-lying, poor ventilation of the trees is weak, which is conducive to disease. In 2001, grape downy mildew occurred in Shenyang. Many vineyards in agricultural production suffered from loss of vineyard leaves when the fruits were not yet fully mature. The production was severely reduced, and some were even absolute. Shenyang region usually starts from July to August, and September to October is the peak period of onset. Third, control methods 1. Eradication of pathogenic bacteria in the autumn to thoroughly clean the orchard, cut off the diseased, collected diseased leaves, concentrated deep or burned. 2. Strengthen the orchard management to timely summer shear, bind the branches, and improve the ventilation and light transmission conditions. Pay attention to weeding, drainage, and reduce the humidity on the ground. Appropriate application of phosphorus and potassium fertilizers, application of lime to acidic soil, improve plant disease resistance. 3. The agent controls and sprays 5 degrees (Baume specific gravity) of lime sulfur before sprouting. Before the onset of disease, it was used to spray 1:0.7:200-240 Bordeaux mixture against other diseases. After the diseased leaf was found, sprayed with 40% diethylphosphorus aluminum wettable powder 200-300 times or 25% toxic manganese zinc wettable powder 600 times liquid. Alpha-aluminum and Rhizoctonia spp. have special effects on downy mildew, and if they are used for a long period of continuous use, they will rapidly develop drug resistance, so they should be used interchangeably with Bordeaux mixture. For example, it can not only increase the synergistic effect, but also delay the development of drug resistance of pathogens, such as the use of agents such as zeson zinc, mancozeb, and dandan. In addition, DuPont series products can also be used to spray the US DuPont eBay 800-1200 times before the onset of disease, 7-10 days interval, a total of 3-4 times a significant effect. In the early stage of disease, 600 to 750 times of gypsum is sprayed or 2000 to 2400 times of fast and clean can also receive better control effect. In order to delay the drug resistance, Kelu and Depression can be used interchangeably. When the disease is more serious, drugs should be mixed to ensure efficacy.
Alpha-Naphthyl Acetic Acid,Plant Growth Regulators,Growth Inhibitor
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