Symptoms This disease mainly affects the roots, leaves, shoots, bulbs, etc. of hops. At the beginning of the disease, only the tip of the petal was yellowed and gradually expanded downward. The color changed from pale yellow to gray until all died, and finally it was light brown to brown. Leaf lesions produce irregular multi-use lesions with a mildew layer on the back.
Pathogen Pseudoperonospora humuli (Miyabe et Tak.)Wils. It is known as the flagellin and subphylum fungi. The sporangia sessin is colorless, with false bifurcation branching, branching 2-4 times, small stalk tip tapering, pedicel length 530um. The sporangia is colorless to light grey, pear-shaped, and mastoidous, with a size of 26–4719–22 (um). The oospores are round to near-circular, with a size of 33-3620-2(um), colorless to light gray, double wall;
Transmission Pathway and Pathogenic Conditions The pathogenic bacteria used in the root buds of the diseased plants for latent overwintering was the source of infestation early in the year. The oospore does not work in the infection. In drought conditions in western Gansu, the ball flowering period began in August. The onset of budding after budding, sporangia of the diseased part, re-infection when conditions are appropriate, and constantly expanding damage, causing widespread disease. During this period, there was heavy rainfall, heavy rainfall, and high density of flat crops. Flat ventilation is easy to disease.
Control methods (1) Improved cultivation techniques for leveling as ridges, flattening nets for three-dimensional nets; appropriate thinning, 667m2 Liumiao 220-250 strains are appropriate. (2) Appropriate cuts are made when spring cutting buds are applied, and 90% ethidiumphosphine aluminum wettable powder 400 times fluid or 58% metalaxyl manganese zinc wettable powder 500 times fluid is poured; 58% metalaxyl manganese is sprayed after budding; Zinc, 64% anti-virus M8 WP 500 times, 72% Kelu or Keshuang or frost tyrants WP 700 times, 69% Zn WP 1000 times. Every 7-10 days once, continuous control 2 times.
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