How does persimmon corner spot happen? What are the symptoms? How to prevent and cure it?

Persimmon corner spot is a very troublesome disease that harms persimmon trees. Often let growers have one or two big ones. So how did persimmon corner spot happen? What are the symptoms? How to prevent and cure it? Below, the editor of Tuliu.com will take you to understand it.

First, symptoms

It mainly harms the persimmon stalks and leaves of persimmon and Jun Qianzi. After the damage of the leaf, the yellow-green disease spot appeared on the front of the leaf at the initial stage, the shape was irregular, the edge was blurred, and the vein of the leaf inside the spot turned black. With the expansion of the lesion, the color gradually deepened, showing a light black, and then the middle color faded to a light brown. As the expansion of the disease spot is limited by the leaf vein, the shape becomes polygonal, on which there are dense black fluffy particles with obvious black edges, and the back of the disease spot is light yellow at the beginning, then the color gradually deepens, and finally becomes brown or dark brown, but also has a black edge, but it is not as obvious as the front, and the black particles are also rarer than the front. Persimmon stem disease, the four corners of the disease first, showing a light brown to dark brown spot, the shape of polygonal, and then expand inward, the edge is black or not obvious, both sides of the spot produce black velvety particles, the back of the leaf is more than the front of the leaf.

2. Pathogen and infection route

The pathogen belongs to Cercospora, a semi-known fungus of the fungus. The invasion route is mainly spread by conidia invading from stomata by wind and rain. The diseased pedicel left on the tree is the main source of infection and the site of transmission. Generally, the diseased pedicel can survive in the tree for 2-3 years, and the pathogen can survive in the diseased pedicel for more than 3 years. The pathogen overwintered with mycelia in diseased pedicels and diseased leaves, and took the diseased persimmon stalks remaining on trees as the main source of primary infection and transmission center. In June and July of the following year, Rain Water produced a large number of conidia on the diseased stem of the tree overwintering. The conidia invaded from the stomata with the help of wind and rain, and the incubation period was 25-38 days. The disease began at the beginning of August, and the optimum temperature for the development of the pathogen was about 30 ℃. The disease of Yan Yu in September can cause a large number of fallen leaves and fruits. The conidia formed on the disease spot in the same year can be re-infected when the conditions are suitable. The occurrence and damage degree of the disease are closely related to the early and evening rainfall in the same year, such as early rainfall, more rainy days and heavy rainfall from May to August, which is beneficial to the production and infection of conidia. The disease occurred early and produced barren soil, weak tree potential, poor disease resistance and serious disease. The disease is serious in the luminal leaves of the crown, especially in the old leaves. The disease of Broussonetia papyrifera near Junqianzi is more serious when the fog is heavy and foggy for a long time.

III. Prevention and control methods

1. Remove the diseased pedicles hanging on persimmon trees, which is the main measure to reduce the source of germs. Thorough removal of persimmon stalks and elimination of the source of infection can effectively control or reduce the occurrence of the disease.

2. The protective spraying period is 20-30 days after persimmon blossoms. The medicament can be sprayed with 1:3-5 purge 200,300 Bordeaux solution 65% Dysen zinc wettable powder 500600 times, or 70% methyl topiramate 800-1000 times for 2-3 times, which can effectively prevent the occurrence of diseases.

3. To avoid the mixed planting of persimmon and Jun Qianzi, it is necessary to avoid the mixed planting of persimmon and Jun Qian Zi. In order to avoid infecting persimmon with disease, persimmon and Jun Qianzi should be avoided.

4. Strengthen the management of cutting and cultivation, increase the application of organic fertilizer, improve the disease resistance of trees, reduce the humidity of orchards, create conditions that are not conducive to the reproduction of pathogens, and control the occurrence of diseases.

5. Persimmon trees should be planted in well-ventilated and sunny places because of the choice of land, but it is not suitable to develop persimmon trees in low-lying and moist land. The best planting form is square planting in the north and south.