The reasons for summer soybean yellowing may be the following points.
I. Soybean cyst nematode disease: The disease is mainly distributed in soybeans with many years of re-plots and lower groundwater levels. After the disease at the seedling stage, the leaves are yellow-brown, and the growth is slow. When the plants are in serious condition, the plants dwarf and the leaves turn yellow from the bottom. The flowering period is delayed by 5 to 10 days compared with the control. 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.
Second, viral diseases are 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, use 40% omethoate 1000 to 1500 times, or enemy killing, speed killing 0.5 to 10,000 times liquid spray control.
Third, the bean fly disease: mainly occurs in the application of unfermented organic fertilizer more land or heavy land. Seedlings susceptible to disease, the performance of the lower leaves of the plant is normal, the upper leaves are all yellow. Sensory identification: Peel off the root neck, and there are bean fly maggots and worms in the stalk. Control methods: Use 40% omethoate or phoxim 1000 times solution, spray once at the seedling stage and flowering stage, the control effect is better.
Fourth, malnutrition: mainly occurs in the lack of fertilizer fields, or partial application, a single application of a nutrient element fertilizer or severe drought in the 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 grams of monopotassium phosphate 100 grams of water on 30-50 kilograms of leaf spray, can relieve symptoms or disappear, so that the plant returns to normal growth. The use of fog method works better.
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