Groundnut Tikka Leaf Spot Control

Symptoms

Early leaf spot shows roundish brown spots with a yellow halo, mostly on the upper leaf surface. Late leaf spot shows darker, almost black spots with little or no halo, often with a rough surface and visible on both sides of the leaf. As spots increase the leaves yellow, dry and drop off so the plant looks scorched. Heavy defoliation before harvest is the main effect.

Damage

Tikka, the combined early and late leaf spot disease, is the most important foliar disease of groundnut and can cause pod yield losses up to 50 percent. Loss of leaves cuts photosynthesis so pods fill poorly and pegs and pods may detach during digging, lowering both yield and fodder quality. Late leaf spot is usually the more damaging of the two.

Organic & cultural control

Use clean seed and remove and destroy infected crop residue, since the fungus survives on debris between seasons. Follow crop rotation of at least 2 years with non-host crops to lower carryover. Grow tolerant varieties where available. Spray plant extracts or biocontrol agents that have shown some effect, and maintain proper spacing for airflow. Avoid continuous groundnut on the same land which builds up the disease.

Chemical control

Spray a recommended fungicide at first appearance of spots, usually from about 30 to 40 days after sowing, and repeat at 15 day intervals as needed. Protective fungicides such as mancozeb 0.2 percent or chlorothalonil 0.2 percent are common, and systemic or combination fungicides such as tebuconazole or carbendazim plus mancozeb give strong control. Always follow the product label for dose and pre-harvest interval 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

Grow tolerant varieties recommended for your area and use clean seed from a healthy crop. Follow crop rotation of at least 2 years and avoid growing groundnut after groundnut. Sow at the recommended time and spacing, remove and destroy infected residue, and keep fields free of volunteer groundnut. Scout from about a month after sowing so you can start fungicide at the first spots rather than after defoliation.