10.3 Biological Weed Control Methods

Biological weed control is not a widely used practice. It is utilized mainly in range and grasslands. This approach is using some sort of biological predator – perhaps an insect, plant pathogen or even an animal, such as goats to control weedy or invasive plants. Earlier in this book we talked about invasive plants that are introduced from other areas.  Often in their “native” location, there were already insects or diseases that would keep the weed under control. However, in a new environment those species are not always present.  Researchers go to these environments to locate potential biological control agents that can be introduced into the new region where the invasive weed is located, without causing any other unintended negative consequences to the new environment.  Biological control systems take longer to become effective, but they do work well in locations where it is difficult to apply other control measures, such as in wetlands or steep hillsides.

Considerations

It is important to work closely with a specialist in biological weed control.  They understand how to determine what conditions a biological control agent would be most effective.  Biological weed control experts are also aware if proper research has been done to ensure local ecosystems would not be harmed by the introduction of a new insect, plant pathogen or animal.

Examples

Purple Loosestrife is a problem in waterways.  It was first grown in the US as a horticultural crop and in home gardens. Unfortunately, it found a niche in some wetland areas and has become a real problem.

The following video shows an example of biological control research for managing Purple Loose Strife in New Jersey.  Similar practices were also utilized in Minnesota.