Biological Control

Biological weed management means using living organisms to manage weeds. This most often involves releasing a specific biological control agent, such as an insect, nematode, fungi, or bacteria to a weed-infested area and allowing the agent to attack the weeds. This classical approach for biological control often takes a season or two for the impact to be noticeable.

One of the few successful examples of biological control in agronomic crops is the commercial product Collego, a formulated plant fungus (Colletotrichum gloeosporioides f. sp. aeschynomene) that successfully killed northern jointvetch, but had no effect on other weeds species. However, due to such a narrow spectrum of control, there have been few commercial products developed for agronomic crops.

Grazing by livestock is also a form of “biological weed control” but grazing is not always effective when trying to target specific weeds. Most grazing animals are not selective feeders and will feed on their preferred plants, including crop plants.

Studies have shown some insects (ground beetles and crickets) and rodents will feed on weeds or weed seeds, potentially consuming large number of seeds. This requires a suitable habitat and weed seed availability when large number of these feeding insects or rodents are present.

While the conservation form of biological control can play a role in integrated weed management for grain crops, it is a difficult situation to manipulate. Conserving habitat for seed-feeding insects and rodents, including no-tillage and cover crops, is the best recommendation; however specific guidelines are currently lacking.

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