Identification and Life cycle

Egg:The white, sausage-shaped eggs are about 2 mm long. They are deposited singly in cavities chewed by the adult females in the corm or pseudo stem at ground level or between leaf sheath scars on the crown of the banana corm. They are difficult to detect in the field because they are often hidden by congealed sap produced by the banana plant after the cavity is created. Egg laying also occurs in the form of fallen plants. Eggs hatch in 5 to 7 days. .

Larvae: The stout, creamy white, legless grubs have reddish-brown heads and fleshy white bodies. When mature they are about 12 mm long. The grubs are normally found in the pseudo stems up to 2 feet above the ground. Development is completed in 15 to 20 days. The eighth abdominal segment of the larva bears a large spiracle, the remaining segments bearing small spiracles; the last two segments appear truncated, being fused together to form a plate-like structure.

Pupae: Grubs pupate within chambers that are usually close to the surface of the corms. Pupae are white and about 12 mm long. No cocoon is formed. Pupal development is completed in about 8 days. The pupa has an irregular appearance, with the developing wings and limbs being discernable through the pupal case.

Adults: The adult is about 11 mm in length and has a glossy grayish-black or dark brown appearance. The tibia of each of the limbs bears an accessory hook-like claw with which the insect clings to plants. The hard-shelled weevil is has a long snout. Newly emerged weevils are reddish brown before turning black. Female lay an average of 1 egg a day during their life span. Adults are reported to live for as long as 2 years. They are capable of surviving for extended periods without food.

Nature of damage

Injury is caused by grubs (larvae), which tunnel through the corms. Tunnels are circular in cross section, become wider as the grub grows and are filled with dark-colored debris. Extensive feeding damage by grubs results in root destruction, slowed plant growth, reduced fruit production, and, sometimes, toppled plants. The tunneling by the grubs makes the corms susceptible to invasion by secondary decay organisms. Reduced production and growth of suckers occurs when parent plants are heavily damaged. Affected sucker plants can be recognized by their dull, yellowish-green withered leaves.