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