<h1 class="ql-align-justify" > cherry leaf spot disease</h1>
1. Pathogenesis characteristics
After the invasion of this disease, the incubation period is 1 to 2 weeks. A hyphal mass is formed under the epidermis, which breaks through the epidermis to produce conidia, which are later transmitted by rainwater and repeatedly infected. The veins of the front of the infected leaf produce dead spots of different colors, which expand into brown or purple, die first in the middle, and gradually die outwards, with irregular spots. After the appearance of spots, the leaves turn yellow and fall off, and the spots may also form perforation. Pink mold tends to appear on the back of the spots, and sometimes the petioles and fruits may be infected and produce brown spots. The leaves are large and round on sweet cherries, and pink mold can also be produced on the front, and the pathogen usually does not infect the young leaves.
2. Prevention and control methods
(1) Spray control: After the flowers fall, spray prevention and control begins when the disease spots first appear. Usually sprayed once 1:2:160 times Bordeaux liquid, or 65% Daisen zinc wettable powder 500 times liquid, or 70% methyl tolbuzin wettable powder 800 times liquid, or 75% bacillus 500 to 800 times liquid, or 50% phenyl myrin wettable powder 1200 to 1500 times liquid, etc., when administered, generally sprayed every 7 to 10 days, 3 to 4 times continuously. Increase the number of sprays in rainy areas.
(2) Strengthen management: timely ditching and drainage, removing overcrowded branches, and improving the ventilation and light transmission conditions of cherry orchards.
(3) Reduce the source of bacteria: Leaf spot fungus overwinters on the deciduous leaves, so the key to prevention and control is to sweep away the fallen leaves and burn them completely, or plough in late autumn to reduce the source of overwintering bacteria.
<h1 class="ql-align-justify" > second, cherry brown spot perforation disease</h1>
The lesions of the infected leaves in early May are distributed around the necrotic reddish-brown spots, which then expand to a diameter of 4 to 5 mm, with a light brown in the center and a brownish red edge. Some of the combined lesions form large areas of death. Lesions also develop on the surface of the leaves, sometimes with necrotic tissue falling off, leaving symptoms of perforation. The disease causes early defoliation, and the severely damaged trees all fall off their leaves at the end of July or the beginning of August. This phenomenon leads to autumn flowering and the emergence of new leaves. Often in late November or early December new leaves remain on the tree.
(1) Spray 4 to 5 degree stone sulfur compound before germination, or 1:1: (100 to 200) times Bordeaux liquid to kill the germs lurking in the bark. Starting from mid-April, four sprays of phenylmycin, oligoxine or manganese can effectively prevent brown spot perforation. In May to June, 65% zinc of Daisen can be sprayed with 400 to 600 times liquid.
(2) Enhance the tree potential and improve the disease resistance of the tree body. Combined with pruning, completely prune the diseased dead branches, eliminate the fallen leaves and fruits, and bury or burn them in a concentrated manner to eliminate the source of overwintering diseases. (Author: Yu Changchun)