Canada Thistle Control

Mechanisms and Impacts of Integrated Pest Management Strategies for Sustainable Canada Thistle Control Riparian Corridors - WYO-386-03

Canada thistle is one of the most widespread noxious weeds in Wyoming, and is a serious pest in agronomic, range, pasture, and wild lands throughout the state. It causes considerable yield reductions in crops and pasture, is a strong competitor with native plants, and may reduce wildlife habitat quality. Current herbicide control strategies for Canada thistle have been successful in controlling shoot growth, but often fail to successfully control regrowth due to extensive energy reserves in the roots and subsequent shoot regeneration from adventitious buds on lateral and vertical roots. Additionally, the most effective management options are not available in sensitive riparian areas. Several organisms have been examined for the biological control of Canada thistle. The most promising agent to date is the stem mining weevil, Ceutorhynchus litura. It has been shown to negatively impact Canada thistle populations by reducing energy reserves in the roots but has generally provided poor control when used alone. Its ineffectiveness when used alone has been attributed to the ability of Canada thistle to compensate for damage later in the summer when the biocontrol agent has moved out of the plant and into the soil. Integrated strategies that target Canada thistle at the timing when C. litura has had its greatest impact on root reserves but before the plant has compensated should be key to successful control.

Quick Links