Semiochemical-mediated host selection by Xylosandrus spp. ambrosia beetles (Coleoptera: Curculionidae) attacking horticultural tree crops: A review of basic and applied science

Authors: Ranger, Christopher; Reding, Michael - Mike; ADESSO, KARLA - Tennessee State University; GINZEL, MATTHEW - Purdue University; RASSATI, DAVIDE - University Of Padua

Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2020
Publication Date: 8/24/2021
Citation: Ranger, C.M., Reding, M.E., Adesso, K., Ginzel, M., Rassati, D. 2021. Semiochemical-mediated host selection by Xylosandrus spp. ambrosia beetles (Coleoptera: Curculionidae) attacking horticultural tree crops: A review of basic and applied science. The Canadian Entomologist. 153(1):103-120. https://doi.org/10.4039/tce.2020.51.
DOI: https://doi.org/10.4039/tce.2020.51

Interpretive Summary: Exotic ambrosia beetles are destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic, namely, black twig borer, Xylosandrus compactus; granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky); and granulate ambrosia beetle, Xylosandrus germanus. This review focuses on these Xylosandrus species with the goal of describing their host selection behavior, characterizing associated semiochemicals, and assessing how these interactions relate to their management. All three of these species exhibit a capability to attack a broad range of trees and shrubs. Weakened trees in the early stages of physiological stress that may appear healthy are preferentially attacked by X. crassiusculus and X. germanus; the influence of physiological stress on host selection by X. compactus is less clear. Ethanol is emitted from living but weakened trees in response to a variety of stressors, and represents an important kairomone. Verbenone inhibits their attraction to ethanol, but the effect is inconsistent and does not prevent attacks from occurring. Integrating repellents and attractants into a “push-pull” management strategy has been generally ineffective, but could be optimized further. Overall, maintaining host vigor and minimizing the chance for emission of stress-induced ethanol is key for managing these insects.

Technical Abstract: Exotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic, namely, Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). This review focuses on these Xylosandrus spp. with the goal of describing their host selection behavior, characterizing associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. exhibit a capability to attack a broad range of tree and shrubs. Weakened trees in the early stages of physiological stress that may appear healthy are preferentially attacked by X. crassiusculus and X. germanus; the influence of physiological stress on host selection by X. compactus is less clear. Ethanol is emitted from living but weakened trees in response to a variety of stressors, and represents an important kairomone. Verbenone inhibits their attraction to ethanol, but the effect is inconsistent and does not prevent attacks from occurring. Integrating repellents and attractants into a “push-pull” management strategy has been generally ineffective, but could be optimized further. Overall, maintaining host vigor and minimizing the chance for emission of stress-induced ethanol is key for managing these insects, particularly X. crassiusculus and X. germanus.