Canada Thistle
Purple Loosestrife
A Short History
The practice of biological control has been implemented against dozens of exotic weed species worldwide. For over 100 years, classical biological control of weeds has relied on the introduction of host-specific, plant-feeding insects. These agents reduce the competitive advantage of the exotic weed. Successful bio-control stresses the plant, allowing more desirable plant species to displace the weed.

Success Story
The application of biological control methods against exotic rangeland weeds was popularized during the 1940's. During this time the introduction of the defoliating Klamath Weed Beetle, Chrysolina quadrigemina, was made against St. Johnswort. Adults and larvae of this European beetle quickly reduced the abundance and density of this weed to that of a roadside pest. Introduction of additional agents further stressed this perennial weed in drier areas where the Klamath Weed Beetle was not quite as effective. Since that time, there have been other successful cases illustrating the value and practicality of biological control against exotic plants. If you are interested in receiving additional information on these biological control successes, please give us a call. We would be glad to speak with you.

The National Bison Range has had great success with the use of beetles on St. Johnswort. The acting Refuge Manager stated: "It's very dramatic to go from 6,000 to 100 acres of the weed".

Agricultural Research Magazine, 12/94

Biological Control of Weeds, Inc.
1418 Maple Drive • Bozeman, MT 59715
Phone 406-586-5111

Email: bugs@bio-control.com