Bionomics of Scolytus schevyrewi (Coleoptera: Curculionidae) in Saskatchewan and Manitoba, Canada

The invasive alien Scolytus schevyrewi Semenov (Coleoptera: Curculionidae: Scolytinae) was detected in Saskatchewan and Manitoba, Canada, in 2007. Because S. schevyrewi is a potential vector of the Dutch elm disease pathogen (Ophiostomanovo-ulmi Brasier; Fungi: Ophiostomataceae), the natural history of the beetle was studied from 2009 to 2012 in the two provinces, where the disease is managed to protect Ulmus americana Linnaeus (Ulmaceae). Typically, healthy trees become infected when their xylem is contacted during feeding by spore-bearing scolytine adults that have flown from a diseased tree; adults emerging from brood galleries in diseased trees frequently carry spores. We caught flying S. schevyrewi adults from May to October; adults were weakly attracted to healthy Ulmus Linnaeus but were strongly attracted to Ulmus pumila Linnaeus stressed by girdling. Scolytus schevrewi colonised and completed development in girdled trees and trap logs of U. pumila. In contrast to other studies, U. americana – the major source of pathogen spores in the area – was never colonised as a brood host. Our results suggest that S. schevyrewi will primarily use U. pumila, which, in Manitoba and Saskatchewan, seldom exhibits symptoms of Dutch elm disease. Thus, arrival of S. schevyrewi does not appear to require changes to Dutch elm disease management programmes.