Watermelon root rot is a newly occurring disease in watermelon in Zhongmu County in recent years. It occurs early, spreads rapidly, and is a serious and serious loss. From 1997 to 1998, 2a consecutive years of pandemic in Zhongmu County, the affected area of ​​10,000 hectares, accounting for 38% of the county's watermelon planting area, yield loss of more than 30%. In 1999, the disease recurred in large areas on protected areas in Zhongmu County and cultivated watermelons in open fields. To this end, we conducted an investigation of the disease. 1. Symptoms The disease mainly affects the roots of the melons and stems and rarely affects stems. After the colonization, the onset of disease can begin, the watery appearance is early, and then it is light brown to dark brown rot, the disease part does not contract, the vascular bundle becomes brown, but does not expand upwards, can be distinguished from withered blight disease, the latter part of the disease often Worse, the tissue breaks, leaving only filamentous vascular bundles. Victim vines were initially upturned with tiny curls and grew slowly. Afterwards, the leaves of the entire plant wilted at noon and recovered sooner or later and gradually died. 2. After the pathogen was isolated and cultured, it was identified as FusariumsolaniTM (Mart.) App. et Wollenw. The melon Fusarium solani was classified as a fungus of the subphylum Aspergillus. 3. Onset of the disease According to the field survey conducted in 3a, the watermelon in protected areas began to develop in mid-February, and in the middle and early March, the incidence was high. The rate of diseased plants was 35% to 60%. Severe cases were watermelons in a large greenhouse in Dahong Village, Hansi Town. Infected, re-infected after the onset of the disease, causing no harvest. The open-water watermelon is the initial stage from late April to early May, and the epidemic stage occurs in the middle and late May. The rate of diseased plants is as high as 80%. At the same time, in the survey, watermelon root-knot nematodes were also found to be harmful to melon fields, and watermelon root rot was also a serious disease. Sunny days, little rain, disease development is slow, light damage; after rainy days or watering, the disease develops quickly, and it is seriously harmful; the incidence of continuous cropland, clay land, saline-alkali land and low-lying land is heavy. 4. Prevention and control measures From the perspective of 3a large-scale control effect, at the early stage of disease, use thiophanate-methyl 50% WP 600 times, or 50% carbendazim WP 500 times, or 40% polysulfide suspension 600 Dilution, or 77% can kill WP 500 times, or 14% pluronic emulsion spray 300 times, have good control effect. When the onset is severe, 50% acetaminophen wettable powder 1000 times solution and 70% mancozeb WP wettable powder 1000 times are used to irrigate the root. The effect is very good.
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