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Biological Control

Biological control involves organisms (usually insects, but can include livestock grazing) that are deliberately introduced in an area to control invasive species. The aim of biological control is not eradication, but rather to exert enough pressure on a species to reduce its abundance to acceptable levels (Wilson and McCaffrey 1999). Biological control works best for:

  • reducing seed production or weakening plants;

  • large, dense infestations where other control methods are not cost-effective; and

  • situations where a reduced but effectively permanent presence of an invasive species is acceptable.

Livestock grazing is most useful for:

  • invasive plants that are palatable (at least at some point during the year) and non-toxic to livestock;

  • low level, widespread invasive species infestations where other control techniques are not cost-effective; and

  • areas accessible to livestock (goats, sheep, and cattle) that have adequate water and fencing.

Buffelgrass is generally not controlled by livestock grazing alone. If this method of control is selected for use, a combination of other integrated management approaches must be implemented to achieve control. For example, livestock grazing may be useful for stimulating buffelgrass plant growth prior to a chemical treatment during certain periods of the year when the plant is actively growing. Insect biological control for buffelgrass is currently not available, and no known research has been undertaken to determine a biological control agent for this invasive grass. Works Cited: Wilson, L.M. and J.P. McCaffrey. 1999. Biological control of noxious rangeland weeds. Pp. 97-115. In: R.L. Sheley and J.K. Petroff (eds.). Biology and Management of Noxious Rangeland Weeds. Oregon State University Press. Corvallis, Oregon. 438pp.


Examples of biocontrol in other plants