Biological Control

Biological weed management means using living organisms to help manage weeds. This involves releasing a specific biological control agent, typically an insect, nematode, fungi, or bacteria to a weed-infested area and allowing the agent to attack the weeds. Each biological control agent targets a specific weed species. Grazing by livestock can also be used for “biological weed control,” but grazing is not always effective for targeting specific weeds.

Producers interested in trying biological controls should read the resources below and thoroughly research the agents they are interested in before dispatching them onto a field.

Currently available biological agents

A variety of biological agents are currently in use or are being evaluated for their effectiveness and safety. Both US-native and imported agents are available through retailers, and several states have institutions that provide agents to landowners at no cost for research purposes. Biological agents are available for the following weeds (not an exclusive list):

Leafy spurge, knapweeds, St. Johnswort, yellow starthistle, bull thistle, musk thistle, Canada thistle, tansy ragwort, toadflax, poison hemlock, purple loosestrife, scotch broom, puncturevine

Development and Approval Process

The Animal and Plant Health Inspection Service (APHIS) has to approve the use and distribution of all biological control agents before they can be released to the public. They are tested rigorously to make sure they do not pose a threat to non-target plants. Because of this, it takes up to 20 years for an agent to be fully developed, tested, and approved.

Resources for implementing biological control:

Educational information:

Biological Control of Weeds – Weed Science Society of America

Integrated Weed Control Project – focus on biological control resources – Washington State University

Biological and Integrated Control of Musk Thistle in Missouri – University of Missouri

Association of Natural Biocontrol Producers

Biological Control Program – USDA APHIS

International Code of Best Practices for Classical Biological Control of Weeds – Washington State University

Biological Control News archives – University of Wisconsin

Ordering biological weed control agents and consultation:

Available Bio Control Agents for Weeds – Washington State University

Weed Biocontrol and Requesting Agents – Colorado Dept. of Agriculture

Biological Products and Consulting Services – Integrated Weed Control Company

Biological Control Agents – Biological Control of Weeds, Inc.