BIOCONTROL OF THE WEED CANADA THISTLE (CIRSIUM ARVENSE): RELEASES AND DEVELOPMENT OF THE GALL FLY UROPHORA CARDUI (DIPTERA: TEPHRITIDAE) IN CANADA

Publisher Website
Google Scholar
Abstract
The gall fly Urophora cardui (L.) (Diptera: Tephritidae), native to Europe, was released at 24 locations across Canada beginning in 1974. It became established in Ontario, Quebec, and New Brunswick but died out in all but one location in western Canada. Evidence for winter mortality in the west does not explain the failure of these colonies. Although galls, in particular those on the main shoot, reduce the height of Canada thistle, so far the impact on the host weed, Canada thistle (Cirsium arvense) (L.) Scop., is slight.