Development of RNAi for Suppression of Exotic Wood-boring Buprestids

Non-native wood-boring beetles are arriving in US ports at alarming rates (3), often entering our forests and remaining undetected until after establishment, making eradication virtually impossible (5). Buprestidae, including the emerald ash borer, Agrilus planipennis (EAB), are wood-boring beetles that feed as larvae on phloem beneath tree bark, girdling stems and branches and killing trees. Our native trees are highly susceptible to attack by exotic woodborers and are unable to ward off attack; trees die rapidly (6). Chemical suppression is not sustainable due to their aggressive nature, widespread distribution of susceptible hosts, and economic and ecological concerns (10-13). Classical biological control can be successful, but the time required for discovery and establishment often results in extensive tree mortality (1,4). The emerald ash borer is just one example of a non-native buprestid capable of devastating our forests. Closely related Agrilus species, including the oak splendor beetle, A. biguttatus, the goldspotted oak borer, A. auroguttatus, and A. smaragdifrons, are listed on the NAPIS Exotic Pest Tracker (14). We are developing techniques to utilize an innovative pest suppression approach, RNA interference (RNAi), to target wood-boring Buprestidae, focusing on aggressive, non-native species (7-9). RNAi is a gene-silencing mechanism that is an emerging approach to insect pest management. This interference manifests itself in compromised development, reduced fecundity, or direct mortality. RNAi is highly specific to the target species, and there is considerable variability in the efficacy of RNAi between different species. We've discovered that RNAi works in the aggressive, invasive emerald ash borer (EAB) (7,15). Optimal gene selection is progressing, and this could be a promising approach for closely related species. However, demonstrating the specificity of the selected genes, and developing appropriate delivery methods of the dsRNA to the target is essential for implementation of RNAi as a management approach. These are the objectives of this proposal.