Semiochemical-mediated host selection by<i>Xylosandrus</i>spp. ambrosia beetles (Coleoptera: Curculionidae) attacking horticultural tree crops: a review of basic and applied science
Christopher M. Ranger, Michael E. Reding, Karla M. Addesso, Matthew D. Ginzel, Davide Rassati
Abstract
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: Xylosandrus compactus (Eichhoff), Xylosandrus crassiusculus (Motschulsky), and Xylosandrus germanus (Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of these Xylosandrus spp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked by X. crassiusculus and X. germanus , but the influence of stress on host selection by X. compactus is less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push–pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularly X. crassiusculus and X. germanus .