Pre-invasion assessment of exotic bark beetle-vectored fungi to detect tree-killing pathogens

Exotic diseases and pests of trees have caused continental-scale disturbances in forest ecosystems and industries, and their invasions are considered largely unpredictable. We tested the concept of pre-invasion assessment of not-yet invasive organisms, which enables empirical risk assessment of potential invasion and impact. Our example assesses fungi associated with Old World bark and ambrosia beetles and their potential to impact North American trees. We selected 55 Asian and European scolytine beetle species using host-use, economic, and regulatory criteria. We isolated 111 of their most consistent fungal associates and tested their effect on four important Southeastern American pine and oak species. Our test dataset found no highly virulent pathogens that should be classified as an imminent threat. Twenty-two fungal species were minor pathogens, which may require context-dependent response for their vectors at North American borders, while most of the tested fungi displayed no significant impact. Our results are significant in three ways: they ease the concerns over multiple overseas pests suspected of heightened potential risk; they provide basis for focus on the prevention of introduction and establishment of species that may be of consequence; and they demonstrate that pre-invasion assessment, if scaled up, can support practical risk assessment of exotic pathogens.

Bark and Wood Boring Insects—Past, Present, and the Future Knowledge We Need

Bark and wood-boring insects represent a very diverse group of insects that includes bark and ambrosia beetles, cerambycids, weevils, jewel beetles, or even anobiids from the order of beetles (Coleoptera), but in the broader sense other insect orders like Lepidoptera (e [...]

Semiochemicals for bark beetle (Coleoptera: Curculionidae) management in western North America: where do we go from here?

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.

Disruption of coniferophagous bark beetle (Coleoptera: Curculionidae: Scolytinae) mass attack using angiosperm nonhost volatiles: from concept to operational use

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.