This paper is intended as an assessment of the state of knowledge and development of semiochemical methods for control of bark beetles (Coleoptera: Curculionidae) in western North America and as a roadmap for future research and development in this field. It is based on a keynote presentation given at the symposium Managing Bark and Ambrosia Beetles with Semiochemicals, held in 2018 in Vancouver, British Columbia, Canada, at the Joint Meeting of the Entomological Society of America, the Entomological Society of Canada, and the Entomological Society of British Columbia. We describe currently available active ingredients, formulations, and release devices. Furthermore, we describe the most urgently needed new products and techniques, and constraints to their further development. Finally, we speculate about opportunities afforded by new advances in microbial synthesis of semiochemicals, streamlining of regulatory processing, and aerial application using unmanned aerial vehicles.

Although the use of nonhost plants intercropped among host crops has been a standard agricultural practice for reducing insect herbivory for millennia, the use of nonhost signals to deter forest pests is much more recent, having been developed over the past several decades. Early exploratory studies with synthetic nonhost volatile semiochemicals led to targeted electrophysiological and trapping experiments on a variety of bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) across three continents. This work disclosed a suite of antennally and behaviourally active nonhost volatiles, which are detected in common across a range of coniferophagous bark beetles. It also established the fact that dispersing bark and ambrosia beetles detect nonhost signals while in flight and avoid nonhost trees without necessarily landing on them. Later work showed that groups of synthetic nonhost volatiles, sometimes combined with insect-derived antiaggregants, are effective in protecting individual trees and forest stands. Further work in this system may lead to the development of a variety of new and useful tactics for use in various integrated pest management strategies.

On 14 November 2018, a symposium Managing bark and ambrosia beetles with semiochemicals was held in Vancouver, British Columbia, Canada, at the Joint Meeting of the Entomological Society of America, the Entomological Society of Canada, and the Entomological Society of British Columbia. The focus was on the application of behavioural chemicals for management of bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in conifers and hardwoods in North America and Europe. Contributors included nine invited speakers from Canada, Slovakia, and the United States of America who summarised the current state of knowledge and latest technologies and shared career-long experiences and insights. This special issue features publications derived from those presentations.

The red turpentine beetle, Dendroctonus valens LeConte, 1860 (Coleoptera: Curculionidae, Scolytinae), is a common bark beetle found throughout much of North America and China. In 2004, we observed that attack densities of the California fivespined ips, Ips paraconfusus Lanier, 1970 (Coleoptera: Curculionidae, Scolytinae), in logging debris were inversely related to D. valens attacks on freshly cut stumps, which led to the demonstration that components of the aggregation pheromone of I. paraconfusus inhibited the response of D. valens to attractant-baited traps. In this study, we test the response of D. valens and Temnochila chlorodia (Mannerheim, 1843) (Coleoptera: Trogositidae), a common bark beetle predator, to racemic ipsenol, racemic ipsdienol, and (−)-cis-verbenol (IPSR) in the presence and absence of two release rates of (−)-verbenone. The addition of a relatively low release rate of (−)-verbenone (4 mg/24 h) to attractant-baited traps did not affect catch and had no significant effect on the response of D. valens to IPSR. IPSR significantly reduced D. valens attraction to baited traps. The addition of high release rates of (−)-verbenone (50 mg/24 h) to IPSR significantly increased inhibition; however, the effect was not significantly different from that observed with (−)-verbenone alone (50 mg/24 h). Temnochila chlorodia was attracted to traps baited with (−)-β-pinene, (+)-3-carene, and (+)-α-pinene. The addition of (−)-verbenone (50 mg/24 h) significantly increased attraction. Traps baited with IPSR caught significantly more T. chlorodia than those baited with (−)-verbenone. Few other beetles were collected. We are hopeful that these results will help facilitate the development of an effective tool for protecting Pinus spp. from D. valens infestations.

The red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), is a common bark beetle species found throughout much of North America. In California, D. valens and the California fivespined ips, Ips paraconfusus Lanier (Coleoptera: Scolytidae), are sympatric and often colonize the same tree. In an unrelated study, we observed that I. paraconfusus attack densities in logging debris were inversely related to D. valens attacks on freshly cut stumps. In this study, we test the hypothesis that allomonal inhibition occurs between these two species. Components of the aggregation pheromone of I. paraconfusus (racemic ipsenol, (+)-ipsdienol, and (–)-cis-verbenol) inhibited the response of D. valens to attractant-baited traps. Substitution of racemic ipsdienol for (+)-ipsdienol did not alter this effect. Doubling the release rate did not enhance inhibition. Racemic ipsdienol was not attractive to I. paraconfusus. Temnochila chlorodia (Mannerheim, 1843) (Coleoptera: Trogositidae), a common bark beetle predator, was attracted to the I. paraconfusus aggregation pheromone. These results could have important implications for the development of an effective semiochemical-based management tool for D. valens.