The origins of infestations of diamondback moth, Plutella xylostella (L.), in canola in western Canada

Abstract

Recent evidence that a population of Plutella xylostella (L.) overwintered successfully in western Canada prompted studies to evaluate overwintering survival of diamondback moth under field conditions in Alberta and Saskatchewan. Successful overwintering was not demonstrated at either site for any life stage under a variety of tillage and organic matter treatments, using either laboratory-reared or field-acclimated specimens of diamondback moth. Diamondback moth infestations in western Canada evidently originate primarily from southern U.S.A. or Mexico when strong winds carry adults northward in spring. To provide early warning predictions of infestations, air parcel trajectories into western Canada were investigated for monitoring long-range movement of P. xylostella early in the season. Using wind fields generated by the Canadian Meteorological Centre’s Global Environmental Multiscale model, three-dimensional air parcel trajectories were calculated using time-forward (prognostic) and time-backward (diagnostic) modes for several sites in North America. The model predicted strong northerly airflow in May 2001 which coincided with the occurrence of massive infestations of diamondback moth in canola in western Canada. The model can therefore serve as an important new tool for monitoring the dispersal of this pest to western Canadian canola crops.