If you're looking for an option to control Canada thistle besides using herbicides, hand picking or mowing, this biological control agent may be right for you. The Canada thistle Stem Mining Weevil (Hadroplontus litura) was introduced from Europe to Canada in 1965 and to the USA in the early 1970's to feed on Canada thistle. The weevil restricts its feeding to this weed and a few close relatives. Weevil feeding may allow a variety of other micro-organisms to enter the thistle stem, with adverse consequences for the thistle: field studies in Montana indicated that underground parts of stems are much more subject to winter kill if the aboveground stem is attacked by weevils during the growing season.
West Central Forage Association has been working with local producers on the release of these weevils for years. Sites where weevils have been released have generally shown decreased stand vigour and patches thin out over time. In 2012, 50 dishes (each containing 105 weevils) were brought up from Montana for producers in the West Central Region who were interested in the purchase and release them in thistle patches. Added to this were 58 dishes for a regional trial set up by the Agricultural Research and Extension Council of Alberta. Yellowhead County releases these weevils as well along the edges of rivers, lakes and streams in or near Right of Ways where herbicide application is prohibited.
If you are interested in purchasing some Weevils please contact:
West Central Forage Association
P.O. Box 360