THE DISTRIBUTION OF RHYZOPERTHA-DOMINICA (F) IN WESTERN CANADA

Rhyzopertha dominica (F.) (lesser grain borer, Coleoptera: Bostrichidae is a major pest of stored grain in the United States, Australia, and most other warm regions of the world. It has rarely been detected in Canadian grain, until recently. To determine the distribution of R. dominica in western Canada, Lindgren multiple-funnel traps baited with R. dominica aggregation pheromones were placed near grain elevators, feed mills, and farms. Rhyzopertha dominica was found flying outside grain-handling facilities in all Prairie Provinces in 1990 and 1991, with thousands collected in Manitoba, hundreds in Alberta, and less than 100 in Saskatchewan. A few R. dominica were caught in Vancouver and Thunder Bay. None were caught in the traps placed beside two grain elevators in southern Ontario. In Alberta and Saskatchewan, the locations with R. dominica were mainly in the south. In Manitoba, the total number of R. dominica caught at each location was higher in the south than in the north. Rhyzopertha dominica were caught as early as 15 May and as late as 18 September, with the peak numbers for a given location occurring between July and September. No difference in the total number of R. dominica caught per year was found among farms, feed mills, or grain elevators in 1990 or 1991. Sampling of stored grain on three farms showed that two of the eight bins sampled had R. dominica. The possible origins of the R. dominica (importation of infested grain, wind-borne migration from the United States, or an established Canadian population) are discussed.