Dept of Agriculture Development 
SFAC KeralaBolls showing regular, circular bore holes Larvae seen feeding on the boll by thrusting their heads alone inside and leaving the rest of the body outside
Presence of granular faecal pellets outside the bore hole.
A single larva can damage 30-40 bolls.
For bollworm, spray quinalphos or chlorpyrifos (2-3l/ha), starting from 55th day of sowing at 15 days interval or more depending on the pest prevalence.
