Peanut diseases are a major concern for farmers, as they can significantly reduce yield and quality. The most common diseases include stem rot, root rot, leaf spot, and rust. Each of these diseases has distinct symptoms and requires specific management strategies.
Stem rot typically starts with dark brown discoloration of the cotyledons, which become dry and begin to rot. As the infection spreads to the base of the stem, yellow-brown, water-soaked lesions appear. These eventually turn black-brown and cause the above-ground parts to wilt and die. To manage this disease, it's important to practice crop rotation, ensure seeds are fully dried before storage, and use high-quality seeds. Seed treatment with 50% carbendazim at 0.2% of the seed weight is effective. When the disease incidence reaches 5%, spraying 50% carbendazim or 70% thiophanate-methyl at 800 times dilution is recommended.
Root rot affects the base of the stem, causing it to become waterlogged and yellow-brown. The plants may appear stunted, and leaves dry from the bottom up. The main lateral roots turn brown and rot, leaving only the primary roots. Control measures include proper crop rotation, selecting healthy seeds, and applying carbendazim at 0.2% during seed dressing. Once the disease appears, a full-field spray with 50% carbendazim at 800 times dilution should be applied.
Leaf spot, which includes brown spot and black spot, manifests as circular, dark brown lesions on the leaves. Brown spots often have a yellow halo, while black spots lack this feature and are smaller in size. The disease is more prevalent in hot, rainy months like July and August. When the infected leaf rate reaches 10%, spraying 50% carbendazim or 70% mancozeb at 800 times dilution every 15 days for two to three applications is advised.
Flower rust is characterized by yellow spots on the lower leaves, surrounded by a narrow yellow halo. As the disease progresses, the epidermis cracks, releasing rusty powders. In severe cases, leaves turn yellow and fall off. Early control involves spraying 75% chlorothalonil at 600 times dilution or 20% triadimefon at 500 times dilution.
In addition to diseases, pests such as locusts, beetles, and earthworms also pose threats to peanut crops. Locusts not only feed on plant sap but also transmit viruses. It’s crucial to monitor early and apply 40% omethoate at 1000 times dilution when infestation reaches 10 per plant.
For underground pests like beetles and earthworms, integrated pest management is essential. Practices such as crop rotation with grass crops like corn or millet help reduce pest buildup. Autumn plowing can expose pests to sunlight or predators, reducing their population. Seed coating with insecticides and soil treatment using 3% formazan granules or chelated phosphate granules before planting are effective methods. During the larval stage, applying phoxim granules or insecticides like 50% phoxim or 90% trichlorfon at 1000 times dilution around the rhizosphere can help control infestations.
By implementing these preventive and control measures, farmers can effectively manage both diseases and pests, ensuring healthier and more productive peanut crops.
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