Swarming caterpillar: Spodoptera mauritia

Symptom of damage:

• Larvae cut the seedlings in large scale
• Cattle grazed appearance in severely infested fields
• They feed gregariously and march from field to field

Identification of insect pest:

• Egg: eggs are spherical and creamy in colour, which are laid in a group covered over with grey hairs
• Larva: caterpillars are light green with yellowish white lateral and dorsal stripes in the early stages and later become dark brown or grayish green in colour with a crescent shaped black spot on the side of each segment
• Pupa: pupates in an earthen cocoon in soil. Pupa is dark brown and measures 16-17 mm long.
• Adult: moth is medium sized, stout built dark brown with a conspicuous triangular black spot on the forewings. Hind wings are brownish white with thin black margins.

Management:

• Flood the nursery to expose the hiding larvae to the surface for birds to pick them up.
• Allow ducks into the field to feed on the larvae.
• Larvae perish in heavy rains, and are victims of various diseases, parasitism and predation.
• Dig trenches around the infested field and place ashes in the trenches to make it difficult for the larvae to escape.
• Insecticides should be the last resort for armyworm control. In nursery, drain the water and spray chlorpyriphos 20 EC @ 80ml + 20 lit of water for 8 cents.
• In main field, spary Chlorpyriphos 20% EC @ 500 ml/ac during late evening in case of severe infestation.