Daily News Archive
Study
Shows Promise of Biological Weed Control
(March
20, 2003)
A University of Colorado
study shows the success of using biological controls to manage weeds
in regions of the western United States. The study, Effect
of biocontrol insects on diffuse knapweed (Centaurea diffusa) in a Colorado
grassland, published in the March-April 2003 issue of Weed Science,
by T. R. Seastedt, Nathan Gregory and David Buckner, examines the effect
of six biocontrol insects on knapweed over a period of five years (1997-2001).
The researchers released four types of insects (knapweed root weevil,
lesser knapweed flower weevil, spotted knapweed seedhead moth, and bronze
knapweed root borer) at a diffuse knapweed site, where two other biocontrol
species (banded gall fly and knapweed seed head fly) were already present.
Absolute cover of the diffuse knapweed declined from 8.3% to 1.9% from
June 2000 to September 2001, the largest declines appearing in areas
closest to where the insects were released. It is not known which specific
species were responsible for most of the weed decline. However, the
lesser knapweed flower weevil larvae seemed to be responsible for a
reduction in diffuse knapweed seed production, which decreased from
5,000 seeds per m-2 in 1997 to less than 100 seeds per m-2. The adult
insects, as opposed to the larvae, affected actual weed cover.
Diffuse knapweed, which covers about 3.2 million acres in the west, is a popular target for pesticide use. However, since the weed will always come back, simply killing it only treats the symptom, according to one of the study's authors, Tea Seastedt, Ph.D., a professor in the Department of Environmental, Population and Organismic Biology at the University of Colorado, Boulder. Using biocontrols instead of chemicals is practical, feasible and sustainable. Read more about Dr. Seastedt's work from his article Biological Control of Noxious Weeds: Using insects to manage invasive weeds, which appeared in the Winter 2000-2001 (volume 21, number 4) issue of Pesticides and You.
If you are interested in biological control, or any other non- or least-toxic pest management strategies, please contact Beyond Pesticides for more information and resources.