Laboratory Evaluation of Biologically-Based Compounds as Antifeedants for the Pales Weevil, Hylobius pales (Herbst) (Coleoptera: Curculionidae)

Abstract

Twenty plant-produced compounds or mixtures and one insect-produced semiochemical were evaluated as potential antifeedants for the pales weevil, Hylobius pales (Herbst). Initially, a choice laboratory feeding bioassay was conducted to screen the compounds and identify antifeedant activity. This was followed by a no-choice dose-response bioassay to further evaluate the most active compounds from the choice test. In the choice test, nine compounds inhibited feeding by H. pales on white pine, Pinus strobus L., twigs after 24 h: borneol, bornyl acetate, cucurbitacin, limonin, myrcene, neem extract, S (+) and R (−) carvone, and verbenone. Five of these compounds remained active after 48 h: borneol, limonin, neem extract, and both carvone isomers. In the no-choice test, 10% concentrations of S (+) carvone and limonin were the most active compounds for both males and females after 24 h. Borneol, verbenone, and R (−) carvone were active for males only. After 48 h, limonin and S (+) carvone remained most active compounds for males, with cucurbitacin and verbenone also showing activity. However, only limonin was active for females. Dose responses (0.1–10% concentrations) were strong for limonin and both carvone isomers. Cucurbitacin, diluted from a 0.3% concentrate, exhibited similar responses at all three doses, indicating that a more concentrated formulation may have potential as an antifeedant for H. pales. Limonin, both carvone isomers, and verbenone also show promise and will be further evaluated in future studies.