Biological Control

Biological control is the intentional use of living organisms to try and suppress the population of a pest to an acceptable level. These insects are natural enemies of the targeted weeds that come from the weed's native ecosystem. View the Biological Control Fact Sheet (PDF).

Direct & Indirect Impact

Biological control agents impact weeds in 2 ways: Direct Impact - destroys vital plant tissues and functions or Indirect Impact - increases stress on the weeds, which may reduce their ability to compete with desirable plants.

Once the insects are introduced to an area, it may take several years for them to become established and to reach a density where it will have an impact on the weed.


Biological control can be integrated with other practices to reduce weed populations. Herbicides can be applied to an area surrounding the bio-release to provide a buffer strip against neighboring properties or areas that do not have noxious weeds.

It is important to keep in mind that biological control is a slow process and will not eradicate noxious weeds.

However, they do have their place in an integrated pest management control plan, it is important to contact the Spokane County Noxious Weed Control Board to determine if this would be an effective control method for your property.