Non-native invasive forest insects of Eastern Oregon and Washington

Abstract

An increasing number of non-native insects are reaching our ports and beyond as a result of global travel and trade, but they may also arrive from other regions of USA. While historically, the forests east of the Cascade crest have experienced relatively few serious invaders, there is a growing concern over the increased potential for invasion by non-native insect species that may displace native species and/or cause significant economic and ecological damage to east-side forest resources. The threat posed by a non-native invasive species is that the forest may lack natural control mechanisms, and the species may become established, spread, and inflict substantial ecological and economic damage before eradication or mitigation measures can be identified and implemented. In general, treatments and practices that improve forest health reduce the risk or effects of widespread insect outbreaks for indigenous species, and have been prescribed to mitigate the effect of non-native species. However, the most effective management options focus on prevention and suppression efforts, which include investigating potential invaders and pathways of introduction, imposing regulatory restrictions, developing and implementing detection and monitoring strategies, and aggressive eradication efforts. Specific management strategies are likely to differ for each potential invader. Examples of east-side invaders include larch casebearer (Coleophora laricella), which has been successfully controlled by introduced parasitoids, the gypsy moth-both Asian and European strains-which has thus far been prevented from establishing in the Pacific Northwest through diligent surveillance and immediate eradication efforts, and the balsam woolly adelgid (Adelges picea), a sap-feeding insect that appears to be an increasing problem in the east side without an immediate solution. An increasing number of introduced wood boring (Coleoptera and Hymenoptera) insects that have been discovered in Oregon and Washington, USA, including at least one east-side site, are also of growing concern.