When a male perceives a female: the effect of waxy components on the body surface on decision-making in the invasive pest weevil

Insects use various semiochemicals for sexual communication and mate recognition; these can therefore be used to govern the behaviours of harmful pest species, and several candidate chemicals have been explored for this purpose. For the West Indian sweet potato weevil, Euscepes postfasciatus , which is one of the most serious pests of sweet potato, no effective capture techniques, such as sex pheromone lures, exist. Toward exploring promising procedures for monitoring these weevils, we assessed the effect of secretions on the body surface on the recognition of congeners and on courtship behaviour in the weevils. Our study clearly demonstrated that weevils responded to extracts from the body surface, and the behaviour adopted by the weevils varied significantly depending on the condition of the extracts. Furthermore, we found a significantly prolonged retention time for males on glass beads covered with extracts of females based on survival analysis. These findings are, as far as we are aware, the first to show the effect of lipid components of the body surface on decision-making in these economically important pest weevils.

Interplanting Different Varieties of a Sweet Potato Crop to Reduce Damage by Oligophagous Insect Pests

One complementary or alternative control measure to chemical insecticide is interplanting of plants that affect insect behavior. While few successes are known based on interplanting of different varieties of the same crop, such intra-crop interplanting may be effective against insects that feed on a limited range of plants and have persistent preference to one cultivar. Here, we report three field trials that examined the efficacy of intra-crop interplanting of sweet potato varieties, Ipomoea batatas (L.) Lamarck (Solanales: Convolvulaceae), on an oligophagous weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae), planting a preferred variety, Beni-masari, together with a less preferred one, Kyushu 166. In the first experiment, Beni-masari was planted as a border around Kyushu 166 and this arrangement decreased tuber damage in the main crop (Kyushu 166), although damage reduction was not statistically significant from monoculture plantings of Kyushu 166. In the second experiment, both varieties were planted in plots spaced 3 m apart to test the attractiveness of Beni-masari to weevils from Kyushu 166. No attractive effects of Beni-masari were observed. In the third experiment, the two varieties were planted in separate plots that were contiguous to each other, and in this experiment Beni-masari preferentially attracted weevils away from Kyushu 166 within 3 m distance, and tuber damage in Kyushu 166 within that zone was reduced owing to the attractiveness of Beni-masari. We discuss the potential of the intra-crop interplanting in pest management.