Apple scab is mainly harmful to leaves and fruits. The main symptoms after onset are black-green to black mold on the surface of the lesion. The leaves are damaged, and the lesions can appear on both sides. The lesions are initially light brown and gradually turn black. The surface produces a velvety black mold layer, round or radial, with a diameter of 3-6 mm. In the later stage, the lesions are convex upwards, and the center becomes gray or grayish black. When the lesions are many, the leaves are distorted and deformed, and even fall off early. The fruit is damaged, mostly in the shoulders or crotch, initially yellow-green, gradual dark brown to black, round or oval, with black mildew on the surface. As the fruit grows, the diseased part becomes a depression due to the stop of growth, and the diseased part is cracked and the diseased fruit becomes a deformed deformed fruit.
Pathogen and pathogenesis
The scab is a fungal disease. The pathogen is an apple black star. The pathogen can be harmed from the time of flowering to the ripening stage. The black mold produced on the surface of the lesion is a large number of pathogen spores. The pathogen of Scab is mainly wintering in the deciduous and bud scales. During the second year of growth, a large number of spores are produced, which are transmitted by airflow or wind and rain, infecting young fruit. After 15 days of disease on the leaves and fruits, the spores of the pathogens produced on the lesions were transmitted through the wind and rain, and repeated infections were repeated.
The fruit is affected, and the disease begins from the expansion period. The disease is serious in the late stage of expansion, and the onset of maturity is better. The incidence of early rain and heavy rainfall is early and heavy, especially the rain from May to June is an important factor in determining the severity of the disease; summer rains are continuous and the disease is fast. There was a significant difference in the susceptibility between apple varieties, which was mainly caused by small flat fruit varieties.
Control method
Black spot disease is the object of quarantine. When preventing and treating this disease, we should first do a good job in quarantine work, and then carry out chemical control in a timely manner on the basis of doing a good job in the health of the orchard.
(1) Strengthening plant quarantine It is strictly forbidden to mobilize scion and seedlings from infected areas to prevent the spread of black star disease areas.
(2) Do a good job in the orchard before the defoliation to the germination, thoroughly clean the leaves, concentrate deep or burn, to avoid the bacteria overwintering on it. It is not easy to clean the deciduous orchard. In the early spring, before the pathogen spores mature and scatter, the ground leaves are sprayed with 10% ammonium sulfate solution or 5% urea solution to kill the overwintering bacteria in the diseased leaves.
(3) Prevention and treatment of pesticides in the growing season
The key is the spraying period. It is most important to stop the growth period after the flower falls to the spring shoot. It should be sprayed and controlled according to the rainfall situation. Once in 10-15 days, severe areas should be sprayed 3-5 times in a row. Spraying is best before rain, but it is necessary to use rain-resistant scouring agents. The pesticide bactericides that can be used in the early stage are 80-800 times of 80% mancozeb wettable powder, 1000 times of 68.75% easy-to-water-dispersible granules, 800 times of spray-expanded suspension, 600 times of Prudential WP, 600 times, etc. The use before the onset has a certain preventive effect on black spot disease. In the early stage of the disease, 12.5%% of nitrile emulsifiable concentrate can be used 1500 times, 25% of Jinlix emulsifiable concentrate is 4000-5000 times, and 40% of Fuxing emulsifiable concentrate is 6000-8000 times. Adding 3000-4000 times of soft water to each dose can significantly increase the control effect.
Dr. Boronidazole http://
Stainless Steel Castings,Stainless Steel Coupling,Stainless Steel Parts
Chuang Hong Mei Metal Products Co., Ltd. , http://www.tzcastingmfg.com