Prevention and control of gray mold in the greenhouse

Amaranth, alias grass stalactites, sungrass, lazy dishes, etc., with its unique spicy smell, has become a favorite vegetable variety for urban and rural people. Amaranth is a cold-tolerant vegetable with strong adaptability and is one of the main varieties in the solar greenhouse. In recent years, the solar greenhouses in high-efficiency demonstration parks across the country have been frequently planted in recent years, and gray mold has frequently occurred. It has become the main disease of shed leeks, affecting the yield and quality of leeks. The onset symptoms, pathogenesis and comprehensive prevention and treatment methods of amaranth gray mold are introduced as follows for reference.
First, the symptoms. Mainly harmful to the leaves, divided into white point type, dry point type and wet rot type.
1. White-point and dry-tip type produce white or taupe spots on the front and back of the leaf, which develop downward from the tip of the leaf. Generally, the leaf has more front than the back, and the lesion has a fusiform or elliptical shape. Block, half-leaf or whole leaf withered. The dry tip type is rotted downward from the edge of the cutting blade. It is initially water-soaked, and then becomes pale green with a brown wheel pattern. The lesion spreads into a semi-circular or "v" shape and can extend downwards. 3cm, yellowish brown, surface grayish brown or grayish green fluffy mildew.
2, wet rot type occurs when the humidity is high, the surface of the dead leaves is densely ash to green velvet mold, accompanied by musty smell, no white spots on the leaves. In the storage and transportation of leeks, the diseased leaves showed symptoms of wet rot, completely wet and rot, and gray mold on the surface.
Second, pathogens and pathogenesis 1, pathogens. It is a subgenus of the genus Aspergillus, Botrytis cinerea.
2. Incidence conditions. The gray mold of the leek is mainly spread by the conidia of the pathogen; each time the leek is harvested, the germ can be scattered, and the new leaves can be infected by the water flow and the farming operation. The occurrence of the disease is closely related to temperature and humidity. The suitable temperature for mycelial growth is 15-21 °C. Humidity is the main factor inducing gray mold. The relative humidity of air is more than 85%, and the incidence is light or not. Onset, in addition, nighttime leeks are frozen, high temperature during the day, and the humidity is large, and the incidence is heavy.
Third, prevention and treatment methods 1, agricultural control (1) selection of disease-resistant varieties. <Henan Province Fugou County Amaranth Research Institute production> Hanqing 韭 f f1 cold green king f1 and other varieties of high resistance to gray mold, 791, Pingyi No. 4 varieties followed, Hanzhong 韭 does not resist disease. (2) Clean the shed. After the leek is harvested, the sick body is removed in time, buried or burned to prevent the spread of germs. (3) Turning the fields to dry. Turning the soil between the rows helps to ripen the soil and kill some of the underground pests. (4) Ventilation and dehumidification. Prompt ventilation and dehumidification to prevent excessive humidity in the shed is the key to prevention and treatment of the disease. According to the weather changes, the shed film is opened and opened at noon for ventilation and dehumidification, so that the relative humidity of the air in the shed is reduced to less than 70%. The amount of ventilation depends on the growth of the leek, and it is strictly forbidden to put the bottom wind. (5) Cultivate strong seedlings to raise cockroaches. Through the application of organic fertilizer, timely topdressing, watering, weeding, raising cockroaches, enhance plant disease resistance. Before planting, apply 5000-7000 kg of decomposed farmyard manure, 15 kg of diammonium phosphate, 50 kg of grass ash, deep into the soil, and pour large water; timely watering after planting; topdressing twice before frost, topdressing urea per acre 15 kg, timely irrigation after topdressing. (6) Paving and damping between rows. Lay dry straw between the leeks, absorb moisture, reduce humidity, and maintain ground temperature.
2. Chemical control (1) Dust method. In the early evening of the onset of leek, use a duster to spray 70% of the dust or 5% chlorothalonil dust, 1 kg per acre, once every 10 days, continuously or alternately with other control methods. 2-3 times. (2) Smoke method. In the early stage of the disease, use 10% keeling smoke agent, 200-250 grams per acre, or 5% chlorothalonil, 250 grams per acre, 6-8 points, and ignite in the evening. The shed is fumigation. Once every 10 days, use 2-3 times in a row or alternately with other control methods. (3) Spray method. In the early stage of the disease, spray each time before harvesting, rotate 50% carbendazim or 70% thiophanate-methyl WP 500 times, if necessary, 50% speed or 50% Puppyin and 50% Nongliling WP 1000-1500 times, alternately used, once every 7 days, continuous control 2-3 times. Note: When spraying, focus on the new leaves, cuts and surrounding soil.
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