Groundnut Stem Rot Control

Symptoms

Plants suddenly wilt and dry up, often in patches. At the base of the stem near the soil line you see a white cottony fungal growth, and on it form many small round mustard-seed sized bodies that turn from white to brown. The stem and collar rot and the plant can be pulled out easily. Pods and pegs in contact with infested soil also rot.

Damage

Stem rot caused by Sclerotium rolfsii is a destructive soil-borne disease of groundnut and can cause heavy plant death and pod loss, in severe cases over 25 percent or more of plants. The fungus rots the stem base and pods and its hardy resting bodies survive in soil for years, making infested fields a long-term problem, especially in warm moist conditions.

Organic & cultural control

Treat seed with Trichoderma viride or Trichoderma harzianum and apply Trichoderma enriched farmyard manure to the soil before sowing to suppress the fungus. Do deep summer ploughing to bury crop residue and expose resting bodies to the sun. Follow crop rotation with cereals for at least 2 to 3 years. Remove and destroy infected plants and avoid burying loose green residue near the plant base where the fungus thrives.

Chemical control

There is no cure for a rotted plant, so treat seed and protect the crop early. Treat seed with a recommended fungicide such as tebuconazole or carbendazim plus a biocontrol agent. Where disease appears, a soil drench of a recommended fungicide such as tebuconazole or azoxystrobin around affected plants can check spread. Always follow the product label for dose and instructions and consult your KVK or an agronomist before use.

Always follow the product label, the recommended pre-harvest interval, and your local KVK or agronomist. Pesticide approvals change, so verify before use.

Prevention

Use clean seed and treat it with Trichoderma and a recommended fungicide before sowing. Do deep summer ploughing and follow crop rotation with cereals for 2 to 3 years to starve and bury the fungus. Ensure good drainage and avoid waterlogging, and avoid heaping loose organic matter against the stem base. Remove and destroy infected plants and crop residue, and avoid moving infested soil between fields.