Field trial success for fighting banana weevils with fungal compounds

Few things can strike fear into the heart of a banana farmer more than finding an infestation of the banana weevil. Females of this coffee bean–sized insect lay their eggs between the plant’s leaves and stem; after hatching, the larvae can wreak havoc on crops.

“Larvae feed [on] the banana stem tissues, and the plants are unable to maintain [an] upright position,” says Federico López Moya, a biologist at the University of Alicante.

Banana weevils also act as a vector for Panama disease, a major threat to banana crops worldwide. A weevil infestation can lead to a 90% loss in a banana crop’s yield. But pesticides to fight the weevil can cause pollution.

López Moya and his team have now discovered that volatile organic compounds (VOCs) produced by three fungus species can repel the banana weevil. They say these compounds can be used with other methods to manage the pest more sustainably (PeerJ 2025, DOI: 10.7717/peerj.19414).

Two of these fungus species are known to be lethal to insects, so farmers use them in the biocontrol of pests. The third species is used to kill nematodes that can damage roots.

Researchers isolated four VOCs from the fungi: styrene, benzothiazole, 1,3-dimethoxybenzene, and 2-cyclohepten-1-one. Previous research showed the latter two repel banana weevils in lab conditions.

The researchers then did seven field experiments in banana weevil–infested farms in the Canary Islands, the biggest banana producer in the European Union. These involved burying traps at random points in each field, leaving only a small entry for weevils to fall into the trap.

Each trap contained a pheromone to attract weevils, a VOC to repel them, or both. Empty traps containing neither pheromone nor VOC acted as a control. Researchers also monitored how much VOC was emitted at different distances from the traps.

Interestingly, 2-cyclohepten-1-one had no effect in the field, even though it previously worked in lab tests. The authors suggest that, as shown by previous studies, this could be because temperature can affect how these VOCs evaporate, which in turn can affect how banana weevils perceive them.

Styrene and benzothiazole had some effect, depending on weather conditions, but the most compelling result came from 1,3-dimethoxybenzene, which repelled banana weevils from traps even when the trap also contained the pheromone to attract them.

López Moya thinks this result occurs because of how a weevil perceives the repellent through sensors in its antennae, and his team is now studying exactly how the compound interacts with banana weevils.

He says this research shows that, although the repellent’s usefulness is limited, it could be paired with traps in a “push and pull” strategy to sustainably manage banana weevil infestations in the future.