The reasons for summer soybean yellowing may be the following:
The first is soybean cyst nematode disease. The disease is mainly distributed in many years of high-yield soybean blocks and low groundwater levels. After the disease at seedling stage, the leaves are yellow-brown, and the growth is slow. In severe cases, the whole plant withers. After the adult stage, the plants are dwarfed, and the leaves turn yellow from the bottom. The flowering period is delayed by 5 to 10 days compared to the control, and the pods are less. The grain is not full and the color is dark. Sensory identification: Plant roots are undeveloped, with many fibrous roots, few root nodules, and many cyst nematodes (shaped as tiny yellow particles) attached to the roots. Control methods: change crop rotations and prevent drought. A coarse spray of the plant stem base can be applied to the diseased field with 40% omethoate 1000 times. Note that the use of mist control method is less effective.
The second is viral disease. It is mainly distributed in the fields where heavy locusts occur. Plants caused by aphid-borne virus disease caused leaf shrinkage, yellowing, internode shortening, and plant dwarfism. Control methods:
When aphids occur in summer soybean fields, they are treated with 40% omethoate 1000 to 1500 times, or killed and killed at a speed of 0.5 to 10,000 times.
The third is bean fly disease. Mainly occurs in fields or heavily populated plots where unfermented organic fertilizers are used. Seedlings susceptible to disease, the performance of the lower leaves of the plant is normal, the upper leaves are all yellow. Sensory identification: Peeling the roots, there are visible bean maggots and worms. Control methods: Use 40% omethoate or phoxim 1000 times solution, spray once at the seedling stage and flowering stage, the control effect is better.
The fourth is malnutrition. Mainly occurs in fertilizer-free plots, or partial application, single application of a nutrient element fertilizer or severe drought in high-yield plots. Plants have different degrees of leaf yellowing, shrinkage, and growth retardation. Control methods: Spraying Huimanfeng 50-80 ml per acre or Opporum, Green Wind 95 plus 100 g of potassium dihydrogen phosphate to spray 30-50 kg of water on the leaves, so that the symptoms can be relieved or disappeared, and the plants can return to normal growth. The use of fog method works better.
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