The Causes of Summer Soybean Dead Seedlings and Control Measures
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July 27 04:02:43, 2025
In recent years, summer soybean crops have frequently shown symptoms such as yellowing leaves, stunted growth, and seedling death. Through field investigations, the author has identified several major causes of these issues, along with corresponding results and preventive measures, which are outlined below.
Firstly, **Soybean Blight** is a significant cause of early seedling death. Affected plants exhibit brown ring spots on cotyledons, necrosis at the growing points, and overall wilting. Plants may become stunted, with elongated internodes and curled, brown terminal buds. In later stages, bud and leaf drop occur, and the stem tissue near branches turns brown. The seeds are often underdeveloped and remain green even at harvest. To manage this disease, infected plants should be removed immediately, and foliar sprays of 64% Oxythioquinox (600 times dilution) or 75% chlorothalonil (600 times dilution) should be applied promptly.
Secondly, **Soybean Cyst Nematode** infestation leads to yellowing of cotyledons and true leaves, stunted growth, and poor seed development. Infected plants show weak root systems with few nodules and numerous cysts attached to roots. Control methods include increasing organic fertilizer use, maintaining adequate soil moisture, and applying 40% omethoate (1000 times dilution) around the base of the plants.
Thirdly, **Bean Fly Worm Disease** is common in fields with undecomposed organic matter or excessive cultivation. Symptoms include yellowing of upper leaves while lower ones appear normal. Inspection reveals maggots and worms inside the stems. Spraying 40% omethoate or phoxim (1000 times dilution) during the seedling and flowering stages can help control the issue.
Fourthly, **Nutrient Deficiency** often occurs in poorly fertilized fields or where only chemical fertilizers are used. Symptoms include leaf yellowing, reduced growth, and poor plant vigor. A solution of Huimanfeng (50–80 ml per acre) mixed with 100 g potassium dihydrogen phosphate in 30–50 kg of water can help restore plant health.
Lastly, **Herbicide Residue Damage** is a recurring problem, especially when herbicides like superstars or tribenuron-methyl are applied too late in wheat fields. These residues can persist in the soil and affect subsequent soybean crops, causing stunted growth and reduced yields. Similarly, herbicides such as chlorsulfuron are not easily broken down in alkaline soils, leading to phytotoxic effects. Farmers should ensure proper application timing and avoid using banned herbicides. If damage occurs, immediate irrigation followed by foliar sprays of plant growth regulators or fertilizers can help mitigate the effects.
By understanding these causes and implementing appropriate management strategies, farmers can significantly improve soybean crop health and yield.