Spinach is one of the main leafy vegetables in the vegetable growing areas in northern China. In recent years, the area of ​​spinach cultivation in protected areas has expanded year by year, and a new disease of gray spinach, gray mold, has appeared. Due to the lack of relevant information, farmers find that the disease is often at a loss, most People misdiagnosed it as leaf mold, downy mildew or other diseases, wasting a lot of manpower and material resources, causing great losses to production. The occurrence and prevention methods are described below.
Development and development of spinach gray mold
In November 2004, we first discovered gray mold disease leaves in a plastic greenhouse spinach field in the suburbs of Zhengzhou. According to Koch's law, the pathogen was isolated, cultured, ligated, re-isolated and re-cultured, and the pathogen was identified. The investigation was conducted on the incidence, pathogenesis and prevention techniques.
In November 2005, we discovered spinach gray mold disease plants in the spinach plots of Nanle, Huaxian, Neihuang, Xiangyang, Zhongyu, Zhumadian small arch sheds, greenhouses and solar greenhouses in Henan Province. The investigation found that the incidence of spinach gray mold in the greenhouse of Duhedao Village, Jingdian Town, Neihuang County was as high as 100%, and the highest incidence rate was over 65%. On December 2, 2005, in the spinach field in Gaoping Township, Hua County, the incidence of diseased plants was 3% to 5%, and the serious plots reached more than 10%.
symptom
The plastic greenhouse and the small arch shed spinach gray mold mainly damage the lower leaves of the plant, initially producing light brown irregular spots on the leaves, then expanding into light brown moist large spots, and producing gray mold layer on the leaf back lesions, ie germs Conidiophores and conidia. When the humidity is small, the surface of the diseased leaf has yellow-brown irregular spots on the front side, and there is no obvious halo on the edge. The gray mold layer on the back side is not obvious; when the humidity is large, the diseased leaves become dark brown and rot, and many gray mold layers are formed on the front side of the diseased leaves. In the later stage, the leaf lesions are in a "V" shape with a deep and shallow pattern. The growth potential of the diseased plants is weakened, and the commerciality is deteriorated.
pathogen
The pathogen is Botrytiscinorca Pers., which belongs to the subfamily Fungus. The conidia are round to elliptical, concentrated, five-color, and single-spore, with large differences at both ends, such as water droplets. There is no separation of hyphae.
Route of transmission and disease conditions
The bacteria overwinter on the sick body and spread by airflow and rain. Most of the plots cultivated in the arch shed occur, and the spinach cultivated in the open field rarely occurs. The pathogen can be infested at 1～30°C, and it is easy to occur under low temperature and high humidity conditions; the temperature is 15～20°C, the humidity is above 95%, continuous rainy weather is encountered, or the planting density is large, and the ventilation and light transmission conditions are poor. Gray mold is extremely prone to pandemic. The pathogen can infect melons, beans, solanaceous vegetables and a variety of leafy vegetables at the same time, and cross-infection may occur when the field conditions are suitable.
Disease prevention "five-word method "
1 Adjust the protected area to artificially adjust the microclimate, strengthen the field management, adopt ecological control, and avoid the occurrence of low temperature and high humidity conditions. In the rainy days, it is necessary to ventilate and dehumidify in a short time. Under the conditions of low temperature and sunny weather in the winter season, close the tuyere around the greenhouse and raise the temperature of the shed. To fertilize water reasonably, it is necessary to pour water in small water, avoid flooding with large water, and timely drain moisture after watering, reduce air humidity and control the occurrence of disease conditions.
2 In the sunny days before the rainy weather, the protective fungicide should be sprayed in time. The general product is 600 times liquid or methyl thiophanate 1000 times liquid for spray protection.
3 When smoking and rainy weather is cultivated, the Keling smoke agent can be applied in the evening, 250g per 667 square meters, sealed vents after ignition, and ventilated the next morning, for 2 to 3 times.
4 clear and timely remove the diseased leaves and middle and lower old leaves to facilitate ventilation and light transmission. After the spinach is harvested, the sick body is cleaned up in time, the garden is cleaned, and the deep burial treatment is concentrated to reduce the source of re-dip.
5 killing found sporadic disease plants began spraying 70% thiophanate-methyl WP 800 times solution, 75% good speed WP 800 times solution, 50% keering WP 1500 times solution, 50% bacteria Ling Wet Powder 600 times solution, 50% Nonglietic WP 1000 times solution or 40% ash clear suspension agent 500 times solution, even spray 2 to 3 times. However, it is not advisable to spray on cloudy days, and spray control should be chosen on a sunny morning. At the same time, because the spinach plants are short, the middle and lower leaves are mostly squatting on the ground, and it is difficult to spray on the back of the leaves. It is better to add a small amount of penetrant during spraying control to improve the control effect.
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