Banana Weevil
Cosmopolites sordidus
The most important insect pest of banana and plantain, a dark nocturnal weevil whose grubs bore through the corm at the base of the plant. The tunneling starves and topples plants, and heavy attacks on a new planting can cause it to fail outright, with yield losses that can exceed half the crop.
🔎 How to spot it
The adult is a hard-shelled, slow-moving weevil about three eighths to half an inch long, uniformly dark brown to black, with the long downcurved snout typical of weevils, and it hides by day in leaf bases, cut residues, and the soil around the plant. The grub is a fat, legless, creamy-white larva with a red-brown head that tunnels in the corm. Cutting into the corm reveals dark, frass-filled galleries.
🥀 Damage it causes
The grubs riddle the corm with tunnels, cutting the roots and the connection that feeds the plant, so growth slows, bunches are small, and badly attacked plants snap at the base or topple in wind. New plantings are most vulnerable and can be killed before they establish, while in older stands the mat declines and the stand life shortens. The hidden corm damage often goes unnoticed until plants fall or yields drop.
🛡️ Prevent it
Plant only clean, weevil-free suckers or, better, pared or tissue-cultured planting material, since infested suckers carry the pest into new ground. Keep the mat clean: remove and chop up old pseudostems and corm residues that shelter and breed the weevil, and do not leave cut stems lying as harborage. Mulching and good crop hygiene reduce buildup, and rotating land out of banana for a season starves the weevils.
🧯 If it is already here
Trap the adults with split pseudostem or corm pieces laid on the ground, which the weevils crawl under at night so they can be collected and destroyed, and use pheromone traps where available to mass-trap them. Sanitation, clean planting material, and trapping form the core of control, supplemented by beneficial fungi or labeled insecticides placed at the base where infestations are heavy. Because the grubs are inside the corm, prevention outweighs spraying.
💡 Good to know
Banana weevil spreads mainly through infested suckers, so starting with clean or tissue-cultured plants is the most powerful single step a grower can take. Its nocturnal, hide-by-day habit makes the simple trick of laying out corm and pseudostem traps surprisingly effective for both monitoring and removal. Tidy fields with no old residue support far fewer weevils.
🌱 Plants it attacks
4 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.