Controlling Weeds Using Biological Methods


The Ministry of Forests is responsible for the maintenance and improvement of forest and rangeland in B.C. A major problem threatening the productive capability and ecology of some land administered by the Ministry of Forests is the invasion of noxious weeds.

Noxious weeds are plants out of place. Many noxious weeds have been unintentionally introduced into B.C., often from Europe and Asia. They do not naturally occur here. As a result, their natural enemies, which would have evolved with them in their homeland, are not here. Without natural enemies, these plants have reproduced and spread extensively.

In many areas of B.C., uncontrolled spread of noxious weeds has reduced plant diversity, altered plant and animal habitat, and reduced the forage available for wildlife and livestock. Noxious weeds are generally unpalatable, occasionally poisonous, and can sometimes cause physical injuries to grazing animals. Noxious weeds have also infested many newly forested sites. At times, they have reduced the growth of forest seedlings and threatened seedling survival.

Leafy spurge (Euphorbia esula L.) has infested this site in the southern interior of B.C.

Spotted knapweed (Centanurea maculosa) is very common in B.C.

To date, more than 20 species of noxious weeds have infested about 100 000 hectares of grassland and dry forest land in B.C.

Noxious weeds must be controlled to levels that are socially and economically tolerable. The B.C. Ministry of Forests controls noxious weeds on land under its jurisdiction by using a variety of methods. These methods include preventing the spread of noxious weeds and controlling them with chemical, manual, mechanical and biological techniques, and by maintaining good range conditions. Biological control of noxious weeds in B.C. uses plant-specific insects to reduce the number of weeds.

Spotted Knapweed

Diffuse knapweed (Centanurea diffusa) is very difficult to control.

Diffuse Knapweed

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