A Small-Bolt Method for Screening Tree Protectants Against Bark Beetles (Coleoptera: Curculionidae)1

A simple, small-bolt method was developed and refined for evaluating and screening treatments being considered as prophylactics against bark beetles (Coleoptera: Curculionidae: Scolytinae). Using this method, 4 insecticide products (3 active ingredients) were evaluated against the southern pine beetle, Dendroctonus frontalis Zimmermann, intermittently during a period spanning 1 day to 9 months postapplication. Permethrin (Astro®) showed the best residual effectiveness as determined by the small-bolt assay, followed by bifenthrin (Onyxe) and carbaryl (Ferti-Lome® and Sevin XLR PluS®). Bifenthrin has been reported as effective in field tests with D. frontalis and carbaryl as ineffective, lending credence to the small-bolt method. Results with permethrin suggest that a more extensive evaluation may be warranted for this active ingredient. The method as developed provides a useful and efficient tool for identifying preventive treatments that are unlikely to be effective against D. frontalis. Its use for screening ineffective products would limit expensive and time-consuming field evaluations to treatments that show significant promise. With additional refinement, the small-bolt assay may provide most of the benefits of more costly testing methods while offering sufficient flexibility for comparing prophylactic treatments that rely on different modes of action.