This publication provides an easy-to-use identification guide to the primary biological control agents for Canada thistle in South Dakota and the northern plains. Only four of these agents are approved by both state and federal agencies for release in South Dakota. Photographs are provided for the identification of the adult, pupa, and larva of most species. Specialized terminology is limited to that deemed essential for identification and education.
SDSU Cooperative Extension Service
Johnson, Paul J. and Deneke, Darrell L., "Biocontrol Insects of Canada Thistle in the Northern Great Plains" (2008). SDSU Extension Special Series. 9.