Idaho In Action / Noxious Weeds / Control Strategies / Biological Control / Approved Biological Control Agents

Cyphocleonus achates on spotted knapweed

Cyphocleonus achates on spotted knapweed

How are Biological Control Agents Selected?

Biological control organisms are chosen from a large suite of natural enemies in the target plant’s native range. Foreign exploration for biological control agents is the first step in a new biological control program. Typically, scientists, land managers, and cooperators in the target plant’s native and introduced range are assembled to conduct the exploration. This process may take several years, although it is common to identify the first biological control agent candidate within the first year of exploration.

Once candidates are identified, each candidate species undergoes quarantine testing overseas and/or at a U.S. quarantine laboratory. This is an expensive process (approximately $250,000 per year) requiring several years of funding to accomplish. In addition to the monetary cost and the time investment, there are several other hurdles a potential agent must be subjected to before it can be approved for release in the United States.

After agents have been identified, they are tested for specificity using test plant lists developed by experts. Oviposition (egg laying) tests and feeding tests are used to determine the suitability of the test plants for successful development from egg to adult for potential biological control agents. These tests can be no-choice tests, where the insect is forced to feed on the test plant or starve, or multiple-choice tests, where insects are offered a choice among several potential host plants. The data generated from these tests (which typically take 2-3 years to complete) is then submitted by the biological control agent petitioner to the Technical Advisory Group (TAG) for review.

The TAG for biological control of weeds was established in 1987 and is made up of 15 governmental agencies representing the United States, Mexico, and Canada. Once the petition is submitted, the TAG members review it and can recommend an agent’s release which prompts the petitioner to submit a permit application to the Animal & Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ), who then prepares an Environmental Assessment (EA). If the EA reaches a “finding of no significant impact” (FONSI), APHIS-PPQ then issues a permit. There are several “checks” in this process that have the potential to slow down the application for the new agent(s). This agent review process ensures that only host-specific agents will be released, dramatically decreasing the inherent risks associated with releasing a biological control agent into a new area.

Photo: (Cyphocleonus achates) Mark Schwarzlander, University of Idaho.