Powdery mildew is a fungal disease that occurs severely in warm and arid conditions and can harm other tree species in the drupe fruit class in addition to peach trees.
1. Pathogens
There are two pathogens of powdery mildew. One is the tridential filament monocysticus, which occurs more commonly, mainly harming peach leaves, but also endangering young shoots, and its hosts are plum and cherry. The other is Myrtle monoculus, which mainly harms the fruit.
2. Symptoms of harm
After the peach leaves are infected, the front side produces small greenish pale yellow spots with very inconspicuous edges. The spots are covered with white powder (conidia, hyphae, and conidia), and the diseased leaves are wavy. In late summer and early autumn, many small black dots (ascomycetes) often grow on the spots. Diseased leaves often dry out early and fall off. The fruit is more susceptible to disease as a young fruit, with rounded spots, dense white powder, and the shape of the fruit is not correct (often crooked).
Third, the law of pathogenesis
The hyphae of this pathogen are latent on the host tissue or in the bud in a parasitic state; ascomycetes are an important form of overwintering of powdery mildew bacteria, and generally dormantly survive on deciduous leaves. In the early spring of the following year, during the host germination to leaf spread, the pathogen spreads with air and wind in conidia and ascospores, forming a primary infection.
In general years, powdery mildew occurs more often and more severely in seedlings, and the incidence of large trees is less severe and the harm is less. There are great differences in susceptibility between rootstock varieties, with Xinjiang mao peach being the least resistant and the most severe disease. Powdery mildew bacteria are sensitive to sulfur and sulfur preparations.
Fourth, prevention and control methods
1. Enhance the disease resistance of the tree. Pay attention to the combined fertilization of nitrogen, phosphorus and potassium, apply more potassium fertilizer and trace elements such as boron, silicon, copper, and manganese, control the amount of nitrogen fertilizer, avoid growth, and enhance the disease resistance of the tree.
2. Pharmaceutical prevention and treatment. At the beginning of the disease, the diseased fruit is removed in time and buried deeply, and the drug is sprayed at the same time, and the agent is recommended: powder rust ning, pyrazole ether ester, diethyl methylcyclazole, flupiramide, oxime fat, acetylamide, ether ester and other drugs with insecticide suitable for the season.
3. Eliminate the source of the disease. After the peach tree leaves fall and before germination, the leaves, dead branches and diseased fruits of the peach orchard are completely removed, and the peach tree is burned or buried deeply in combination with fertilization to reduce the source of initial infection. In the early stage of bud expansion, spraying stone sulfur compound can eliminate overwintering bacteria. Stone sulfur compound is quite effective in preventing the disease, but it should be stopped when the temperature is high in summer to avoid drug damage.
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