Pseudostem Weevil

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Pseudostem Weevil

Odoiporus longicollis

Insect


In a Nutshell

  • Tiny holes and jelly gum excretions are visible at the base of the leaf sheaths or on the stem of young plants.
  • Larvae are tunneling across stems, leaving abundant frass.
  • Leaves turn yellow and plant growth can be stunted.
  • The weakening of the stem causes plants to break and fall over during windy weather.
  • Bunches or fruits may not develop properly.

Hosts

Banana

Symptoms

The first signs of an infestation are tiny holes and jelly gum excretions at the base of the leaf sheaths or on the pseudostem of young plants. Brownish larval frass is also visible around the holes. Larvae are tunneling across stems, causing serious damage and reducing the transport of water and nutrients to tissues. Leaves turn yellow and plant growth can be stunted. In serious infections, the weakening of the stem causes plants to break and fall over during windy weather or storms. The tissues rapidly become discolored and emit a foul odor because of the presence of opportunistic pathogens in the wounds . In the infested plants all life stages of the weevil are present throughout the year. Bunches or fruits may not develop properly.

Trigger

The adult weevils are black-colored, about 30 mm long, with a pointed head and a shiny armor. They are predominantly nocturnal but may also be found in the daytime during cooler months or cloudy days. They are attracted by volatile substances released by the banana plants. Females cut slits in leaf sheaths and lay white creamy, elliptical eggs superficially inside. After 5-8 days, fleshy, legless and yellowish white larvae hatch and start to feed on the tender tissues of the leaf sheaths. They bore widespread tunnels that can be 8 to 10 cm in length, reaching the stem, the roots or the bunch stalks. Adults are strong fliers and move easily from plant to plant, spreading the pest this way.

Biological Control

Previously, nematodes of the species Steinernema carpocapsae or some species of arthropods have been used against the weevils with some success. Another strategy is to infect the beetles with pathogens, for example with the fungal pathogen Metarhizium anisopliae.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Insecticides containing organophosphorus compounds can be injected into the stem to kill the larvae. After harvest, remove the affected stems and treat them with insecticides (2 g/l) to kill the egg laying weevils remaining there.

Preventive Measures

Take care to use clean planting material from certified sources.,Plant more resistant varieties, if available.,Remove and burn all plant residues as well as broken and decaying plants which otherwise can serve as breeding places for adults.,Use stems split longitudinally placed on the ground as pseudo-traps.,These cut pieces attract adult female weevils to feed and lay their eggs.,As soon as the larvae emerge, these pieces become dry and eventually the larvae die because of dehydration.