Peanut diseases are a major concern for farmers, as they can significantly reduce yield and quality. Common diseases include stalk rot, root rot, leaf spot, and rust. Understanding these diseases and their control measures is essential for effective management.
Stalk rot typically begins with dark brown cotyledons that become dry and decay. As the infection spreads to the stem base, yellow-brown, water-soaked lesions appear. These eventually turn black-brown and cause the plant to wilt and die. Early signs may include water-soaked spots at the base of the stem or main lateral branches. Control involves crop rotation, proper seed drying before storage, and using healthy seeds. Before planting, seeds should be sun-dried and disinfected with 50% carbendazim at 0.2% of the seed weight. When disease incidence reaches 5%, spraying with 50% carbendazim or 70% thiophanate-methyl diluted to 800 times is recommended.
Root rot affects the base of the stem, causing it to become waterlogged and turn yellow-brown. The plants become stunted, and leaves dry from the bottom up. In later stages, the main lateral roots turn brown and rot, leaving only the main roots shrunk and darkened. Control methods include crop rotation, selecting high-quality seeds, and treating them with 50% carbendazim at 0.2%. When the disease starts, spraying the entire field with 50% carbendazim at 800 times dilution is effective.
Leaf spot, which includes brown spot and black spot, appears on the leaves. Brown spots are round, dark brown, and surrounded by a yellow halo, while black spots are smaller, dark brown, and lack a yellow border. To manage leaf spot, use resistant varieties, maintain good crop rotation, and spray 50% carbendazim or 70% mancozeb at 800 times dilution when 10% of the leaves are infected. Repeat the application every 15 days for 2–3 times during July and August, which are critical months for disease development.
Flower rust disease first appears on the lower leaves, starting with small yellow spots and a narrow yellow halo. Once the epidermis breaks, orange-red spores are released. Severe cases lead to yellowing and drying of the leaves. Early treatment with 75% chlorothalonil at 600 times or 20% triadimefon at 500 times dilution helps prevent spread.
In addition to diseases, pests such as locusts, tigers, and earthworms also threaten peanut crops. Locusts feed on the plant sap and act as vectors for viruses. Monitoring is crucial, and when infestation reaches 10 per plant, 40% omethoate at 1000 times dilution can be used.
Tigers and earthworms are underground pests that cause significant damage by disrupting the root system, leading to poor seedling establishment. Effective control requires integrated strategies, including crop rotation with grass crops like corn or millet, autumn deep plowing to expose pests to sunlight or birds, and seed coating with protective agents. Soil treatments with 3% formazan granules (2–3 kg/ha) or chelated phosphate granules in the furrow can also help. Insecticides mixed into organic fertilizers provide long-term protection.
During the larval stage, applying 35–45 kg of phoxim granules mixed with 250–300 kg of fine soil around the rhizosphere, or using 50% phoxim or 90% trichlorfon diluted to 1000 times, can effectively control underground pests.
By implementing these cultural, chemical, and biological practices, farmers can significantly reduce the impact of both diseases and pests, ensuring better yields and healthier peanut crops.
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