Control Methods for Three Major Soybean Diseases
What does soybean dodder look like? What should you do if soybean dodder appears? Dodder, also called yellow silk vine or tangled silk vine, is a malignant weed. It harms many crops, can cause total loss of soybean yield, and occurs commonly in various regions. (1) Morphology: The stem of soybean dodder is yellow, orange-yellow, or yellow-green, smooth and hairless,...
Root rot, sclerotinia rot, and gray leaf spot are three major soybean diseases, and measures should be taken promptly to control them.Root rot: Soybeans can be affected throughout the entire growth period. At the beginning of the disease, dark brown lesions appear at the base of the stem and spread upward to the lower side branches; the pith of the diseased stem turns brown, the base of the petiole constricts, and the leaves droop. For chemical control, seed treatment can be done with 58% metalaxyl·mancozeb or 72% cymoxanil at 0.3%-0.4% of seed weight.
Sclerotinia rot: The disease begins in late July. At first, brown lesions appear on the stems, after which white cottony growth and white granules form on the lesions, and finally the white granules turn black. Black sclerotia can be seen when the diseased stem is cut lengthwise. For chemical control, spray with 50% procymidone 1000-fold solution, or 40% dimethachlon 1000-fold solution, or 50% thiophanate-methyl 500-fold solution.
Gray leaf spot: The disease begins in early to mid-June and enters its peak period in mid-July. In July-August, high temperature and rainy weather lead to severe disease. It mainly harms leaves; in severe cases, the leaves are covered with lesions, the leaves fall off prematurely, and serious yield reduction is caused. For chemical control, in addition to treating seeds before sowing with 70% dexon or 50% thiram at 0.3% of seed weight, 40% carbendazim 100 g mixed with 30 kg of water should also be sprayed per mu during the flowering and podding stage of soybeans.