The banana pseudostem weevil is a monophagous pest. Adults are strong fliers and move from one plant to another.
Eggs are laid singly, at the base of the outermost leaf sheath. The incubation period ranges from 3 to 8 days. Emerging grubs are fleshy, yellowish white in colour and pass through five instars. The entire life cycle takes around 45 days.
Initially the young grubs burrow extensive tunnels in the leaf-sheaths. Tunnels are roughly circular and can reach up to about 8 mm in diameter.
The important symptoms of infestation are small pin head size holes on the lower leaf sheath, gummy exudation, yellowing and withering of leaves, and decaying of peduncles resulting in the immature fruit ripening.
The ascending flower bud and the peduncle inside the pseudostem can be eaten and damaged, resulting in non-emergence of the flower bud.
Infested plants have dull yellow green and floppy foliage. Heavily infested plants produce small bunches, and are easily blown down by the wind.
Management
The planting material should be trimmed to reduce the number of eggs and grubs.
Disc-on-stump traps and old pseudostems can be used for trapping weevils.
Disc-on-stump traps consist of corn slices placed on top of harvested plants cut at the rhizome.
Old pseudostems can be cut into lengths of 20 to 60 cm and split each length, and placed on the ground near the corn bases with the cut surface downwards.
Adult weevils are attracted to the cut stems or corns for shelter, to feed and to lay eggs. When the eggs hatch the life cycle cannot continue as the cut pieces dry out and the grubs die from desiccation.
Manual collection
The weevils can be collected by hand and destroyed. The efficiency of the traps depends on their numbers and frequency of trapping.
Disk-on-stump traps collect 3 to 7 times as many weevils as pseudostem traps.
Administer stem injection of neem Azal at 4:4 with water, swabbing with neem Azal 4 per cent, pseudostem injection of dimethoate at 1:5 with water can be recommended for the effective pest management.
Department of EntomologyTamil Nadu Agricultural University, Coimbatore
