Use of shelterbelt pine trees as ‘stepping stones’ by Hylastes ater in agricultural landscapes

ABSTRACT Hylastes ater and Hylurgus ligniperda, two exotic pine bark beetles in New Zealand, have recently been collected at locations far from pine plantations or other dead pine host material. We investigated if dispersing beetles are reproducing in the roots and root collars of damaged pine trees of shelterbelts (windbreaks) that are common in New Zealand’s agricultural landscapes. The ability of these bark beetles to breed in roots and root collars has been noted previously, primarily on dead trees and stumps. But to our knowledge it has not been empirically studied in New Zealand if roots of standing but physiologically declining (i.e. dying) trees can serve as suitable breeding material. We used a novel and effective root herbivore emergence trap, which is described here, to carry out this study. A total of 37 H. ater were captured across 13 traps and three sites in inland Canterbury; however, no H. ligniperda were found. We confirm that H. ater is able to colonise roots of damaged and declining isolated pine trees and show that shelterbelts can act as ‘stepping stones’ aiding spread and persistence through the landscape.