In the cultivation of pear trees, fruit bagging can improve the appearance quality of fruits, make the fruit surface smooth and delicate, the area of ​​fruit spots and rust spots becomes smaller, effectively prevent and treat pear fruit diseases and insect pests, reduce pesticide residues, enhance the storage of fruits, and improve pear fruit. One of the important technologies for production efficiency. However, during production, it is found that pear fruit bagging can easily cause a new disease, black spot disease, which affects the appearance quality of pear fruit and pear fruit sales to a certain extent.
First, the symptoms
Black spot disease is also known as black butt disease. According to research and identification, the source of black spot disease is pink Trichosporon, the pathogenic bacteria can easily enter the pear bag along the handle with the rain and fog, and gather in the gingiva. After bagging, the humidity in the bag is relatively high, and the air permeability is very poor. The growth and reproduction of pathogenic bacteria occurs mainly from late June to late July, and the onset of the rainy season is at its peak. At the early stage of disease, small black spots with large sharp spots appear around the fruit pods. With the development of symptoms, the diameter of the fruit spot gradually expands, and multiple lesions can be connected together to form a near-circular depression spot around the lenticels. Lesions only occur in fruits. The epidermis does not cause flesh ulcers, and the dark spots in the late growth and storage period are enlarged and slightly sunken. The disease mainly occurs on pears such as emeralds and yellow crowns.
Second, the pathogenic factors
According to a research survey, the severity of black spot disease is directly related to the climatic conditions in June and July of that year. Humidity in the air and excessive humidity in the bag are the main causes of black spot disease. Overcast days and heavy precipitation are serious. On the contrary, the disease is mild or difficult to occur; through field investigation, the worse the permeability of the fruit bag, the higher the incidence of black spot disease, the orchard with high humidity, poor ventilation, light transmission, severe confinement, and partial application of nitrogen fertilizer, black spots The higher the incidence of the disease.
Third, control methods
The cure for black spot disease is to do a good job of prevention and strengthen orchard management.
1. Strengthen the orchard Qingyuan, Qingyuan use a broad-spectrum fungicide Mengfuli (80% mancozeb) or pure spot wheel (80% tebuconazole) full-tree spray; orchard sick branches should be cleaned.
2. Do a good job of orchard pruning to improve the transparency and permeability of the orchard and reduce the humidity in the garden;
3. Calcium supplementation in young fruit, spraying organic calcium before fruit bagging, spraying once every 7-10 days, spraying 2-3 times continuously;
4. Do a good job of drug prevention. After the flowers are used, use Freudel 600-800 times to prevent them. Use high-efficiency bactericides before bagging. Do not use more than 10 days before bagging. You can use Ye Huimei (25%) Azoxystrobin) 1000-1500 times, this spray must ensure the quality, even and thoughtful, the fruit surface, both sides of the blade must be sprayed.
5 timely bagging, bagging should choose air permeability, good light transmittance of fruit bags.
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