ARS | Publication request: Ethanol injection of ornamental trees facilitates testing insecticide efficacy against ambrosia beetles (Coleoptera: Curculionidae: Scolytinae)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2012
Publication Date: February 1, 2013
Citation: Reding, M.E., Oliver, J.B., Schultz, P.B., Ranger, C.M., Youssef, N.N. 2013. Ethanol injection of ornamental trees facilitates testing insecticide efficacy against ambrosia beetles (Coleoptera: Curculionidae: Scolytinae). Journal of Economic Entomology. 106:289-298.

Interpretive Summary: Invasive ambrosia beetles are damaging pests in ornamental tree nurseries in North America. Ambrosia beetles colonize trees (attack) by boring into the trunks of the trees, and creating tunnels and chambers (galleries) to lay eggs. These galleries are inoculated with symbiotic fungi, which is the food source for the adults and larvae. Nursery trees that are attacked by ambrosia beetles tend to wilt and die. Nursery growers try to protect their trees by spraying the trunks with preventive insecticides, but many of the recommended insecticides have not been thoroughly field-tested against ambrosia beetle in nurseries. Field-testing insecticides against ambrosia beetles has been hampered by inconsistent attacks on experimental trees. We developed a technique to ensure ambrosia beetle attacks on experimental trees, which we tested in Ohio, Tennessee, and Virginia. In addition, in those locations we field-tested conventional and reduced-risk insecticides for preventing attacks by ambrosia beetles. Our technique of injecting ethanol into trees successfully induced attacks by ambrosia beetles to allow field-testing insecticides to control the beetles in all locations. In the field-tests, permethrin products were the most effective materials for preventing attacks by ambrosia beetles. Reduced-risk plant-derived essential oils also suppressed attacks by ambrosia beetles. The ethanol-injection technique will enable researchers to better screen treatments for preventing attacks by ambrosia beetles on ornamental trees. Furthermore, the research shows that plant-derived essential oils, which have low environmental impact, show potential as alternatives to conventional insecticides for preventing attacks by ambrosia beetles. Further testing to refine the ethanol-injection technique for use in testing efficacy of treatments to manage ambrosia beetles in nurseries is warranted.

Technical Abstract: Exotic ambrosia beetles are damaging pests in ornamental tree nurseries in North America. The species Xylosandrus crassiusculus (Motshulsky) and Xylosandrus germanus (Blandford) are especially problematic. Management of these pests relies on preventive treatments of insecticides. However, field tests of recommended materials on nursery trees have been limited because of unreliable attacks by ambrosia beetles on experimental trees. Ethanol-injection of trees was used to induce colonization by ambrosia beetles to evaluate insecticides and botanical formulations for preventing attacks by ambrosia beetles. Experiments were conducted in Ohio, Tennessee, and Virginia. Experimental trees injected with ethanol had more attacks by ambrosia beetles than un-injected control trees in all but one experiment. Xylosandrus crassiusculus and X. germanus colonized trees injected with ethanol. In most experiments, attack rates declined 8 d after ethanol-injection. Ethanol-injection induced sufficient pressure from ambrosia beetles to evaluate the efficacy of insecticides for preventing attacks. Trunk sprays of permethrin suppressed cumulative total attacks by ambrosia beetles in most tests. Trunk sprays of the botanical formulations Armorex and Veggie Pharm suppressed cumulative total attacks in Ohio. Armorex, Armorex + Permethrin, and Veggie Pharm + Permethrin suppressed attacks in Tennessee. The bifenthrin product Onyx suppressed cumulative total attacks in Virginia. Substrate drenches and trunk sprays of neonicotinoids, or trunk sprays of anthranilic diamides or tolfenpyrad were not effective. Ethanol-injection is effective for inducing attacks and ensuring pressure by ambrosia beetles for testing insecticide efficacy on ornamental trees.