Protecting Conifers from Bark Beetles (Coleoptera: Curculionidae, Scolytinae) with Insecticides in the Western United States¹

Bark beetles (Coleoptera: Curculionidae, Scolytinae) cause extensive tree mortality in conifer forests in the western United States. One method to protect conifers from bark beetles involves applications of liquid formulations of insecticides to the tree bole using high-pressure (e.g., ≥2,241 kPa) ground-based sprayers. Several active ingredients and products are effective when properly applied in accordance with the label. Researchers recently have developed more portable methods that inject small quantities of systemic insecticides directly into trees. The purpose of this review is to synthesize information on the efficacy, residual activity, and environmental safety of insecticides commonly used to protect conifers from bark beetles in the western United States so that informed, judicious decisions can be made about the use of these insecticides. This review serves as an update to “Advances in insecticide tools and tactics for protecting conifers from bark beetle attack in the western United States” (Fettig et al. 2013a) and focuses, where applicable, on relevant literature published since 2012.