The cardamom thrips, Sciothrips cardamomi ranks first among the insect pests of cardamom and is considered to be the most destructive pest in all the cardamom growing tracts.
The damage is caused by both nymphs and adults as they colonize and breed in unopened leaves, leaf sheath, panicle, flower buds and capsules. They lacerate the plant tissue and feed on the exuding sap.
There will be shedding of flowers and immature capsules. The cardamom pods become shrivelled, undersized, scabby, warty, malformed and lose their characteristic aroma.
The seed formation is also affected. The infested capsules are light in weight, inferior in quality and fetch very low market value.
It is estimated that 78 per cent by weight and 82 per cent by number of capsules are damaged due to thrips.
The adult thrips are tiny, yellowish in colour with fringed wings. They reproduce in large numbers especially during post monsoon seasons. Each female lay around 30 eggs. The incubation and nymphal periods are 8-12 and 10-12 days respectively. Pseudopupal stage takes five days. The complete life cycle from egg to adult takes 25-30 days.
— Maintain thrips resistant Malabar types of cardamom clumps.
— Regulation of shade and removal of alternate host plants like Panicum longipes , Hedychium flavescens etc. in the vicinity of plantations would help in reducing the build up of this pest.
— The panicle and 1/3 portion of the base of the clumps are to be treated with insecticides.
— Spray 5-7 rounds of insecticides like quinalphos 0.025 per cent, phosalone 0.07 per cent , chlorpyrifos 0.05 per cent or profenofos 0.05 per cent at 35 days interval. Approximately 250-500 ml of spray fluid will be required per clump.
— Alternatively dust formulations of quinalphos 1.5 D, carbaryl 10 D or phosalone 4D each at 25kg/ha may also be applied.
— Removal of dried leaf sheaths prior to spraying increases the efficiency of the applied insecticides. It is advisable to do spraying as dusting is found more harmful for honey bees.
J. Jayaraj & Manisegaran
Agricultural College and Research Institute Madurai, Tamil Nadu