Terpenoid lactones with the p-menthane system as feeding deterrents to the lesser mealworm, Alphitobius diaperinus

The application of antifeedants, often in combination with other methods within integrated pest management (IPM) strategies, has proven to be a good way to control insect pests. Little is known about compounds that have antifeedant activity against the lesser mealworm, Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae). The antifeedant properties of optically pure isomers of pulegone and isopulegol and some enantiomeric pairs of bicyclic terpenoid lactones with the p -menthane system, derived from these isomeric starting compounds, were studied in choice and no-choice tests with the lesser mealworm. The original monoterpenes and γ-spirolactones were weak feeding deterrents to larvae and adults of A. diaperinus . The δ-hydroxy-γ-spirolactones showed significant activity against adults, but substituting the hydroxy group with a ketone group considerably reduced the deterrent activity of the resulting δ-keto-γ-spirolactones. The bicyclic γ-hydroxy-δ-lactones with condensed rings and with the (1 S ,6 R ,8 R )-(+) and (1 R ,6 S ,8 S )-(–) configuration of the chiral centres, and δ-hydroxy-γ-lactone (1 S ,4 S ,6 S )-(+) were very strong antifeedants to both larvae and adults. The hydroxy groups and the configuration of the chiral centres of the molecules were very important features for determining the antifeedant activity of the lactones tested. Generally, the compounds studied were better antifeedants to adults than to larvae.