Repellents effectively disrupt the olfactory orientation of Sitophilus granarius to wheat kernels

Sitophilus granarius (L.) (Coleoptera: Dryophthoridae) is one of the most important pests of stored cereals worldwide. Sustainable control means of this pest are urgently needed mainly owing to legislative limits to the commonly used fumigants and broad-spectrum contact insecticides. The effectiveness of one alcohol and seven aliphatic aldehydes, previously identified as repellents, to disrupt adult granary weevils orientation towards wheat grains were assessed in two-choice olfactometer bioassays. In the dose range tested, all compounds effectively reduced wheat grains attractiveness and inhibited the preferential orientation of adult weevils towards the host substrate. Moreover, at the highest doses the three aldehydes butanal, (E)-2-hexenal, and (E,E)-2,4-nonadienal, their binary (1:1) and the ternary (1:1:1) blends induced a significant preferential orientation of insects to the control, indicating actual repellence. Among all repellent stimuli, the ternary blend and the binary blends of butanal plus (E)-2-hexenal and (E)-2-hexenal plus (E,E)-2,4-nonadienal were the most effective. At certain doses, the observed insect response to these blends was more intense than that expected from individual compounds, demonstrating synergistic interactions between the blend components. Repellent aldehydes and their mixtures were effective in disrupting the olfactory orientation of adult granary weevil to a highly attractive oviposition and food substrate. Future development of proper formulations of these bioactive compounds is promising to set up semiochemical-based control means for this pest.