Managing pod borer in blackgram

Blackgram, commonly known as urdbean is cultivated in about 3.30 million hectares in the country.

Among the various pests and infestations attacking the crop, insect pests are a major problem affecting the yield.

Spotted pod borer is a widespread problem. Webbing together of pods, inflorescence and leaves by a dull white or yellowish caterpillar, presence of frass on pods, stem and shoot near the larval entry holes are common symptoms.

Blue butterflies are another major pest. The larvae of these butterflies chew on the leaves, but preferably feed on buds, flower and young pods. The infested pods show irregular or oblong boreholes. The caterpillar looks like a slug.

Small, blue, beautifully sculptured eggs are laid singly on buds. Larvae are medium in size green in colour, oval and flat in shape.

Pupation occurs inside the soil or on plant debris. One generation is completed in about five weeks. A female lays about 120 eggs.

Gram pod borer is popularly called as American boll worm. The borers feed on leaves, flower buds, flower and pods. They bore round holes on pods. The larva can be seen feeding with the head alone thrust inside and rest of the body hanging out of the pods.

A single larva can destroy 30-40 pods before it reaches maturity.

Owing to feeding on developing grains, the yield of pulses is considerably reduced.

— Apply 50 kg potash per hectare to crop raised with closer spacing (20x10cm) to reduce the incidence.

— Remove weeds as and where found . Collect and destroy the egg masses and pupae.

— Set up light traps. Set up pheromone traps @ 12 nos per hectare to reduce gram pod borer incidence.

— Release egg parasite, Trichogramma spp., and egg larval parasite, Chelonus blackburnii for control of gram pod borer.

Apply any one of the following insecticides like Emamectin benzoate 5 per cent SG 220 g per hectare, or Neem Seed Kernel Extract (NSKE) 5 per cent twice.

(Dr. S. Pasupathy is Professor, National Pulses Research Centre,TNAU , Vamban – 622 303, Pudukkottai district. Tamil Nadu, email : sundarampasupathy@rediffmail.com, Mobile : 09443291019.)