Diffuse Knapweed
Biological Control Agents
There is very little diffuse knapweed in Fremont County and, as far as we know, it is in a limited area. Four bio-control agents have been released on a mixed infestation of spotted and diffuse knapweed in the Green Mountain area in southwestern Fremont County.
In 1995 the insects released included: the lesser knapweed flower weevil, Larinus minutus, the green clearwing fly, Terellia virens, and the banded gall fly, Urophora affinis.
Terellia virens is primarily released to target Spotted Knapweed, but is known to attack Diffuse Knapweed to a limited degree. Larinus minutus will attack Spotted Knapweed as well, but has a preference for Diffuse Knapweed.
For more specific information about Larinus minutus, or Terellia virens, visit Cornell University's Bio-control website here and here.
In 1996 an additional mixed release of Urophora affinis and Urophora quadrifasciata was made.
For more specific information about Urophora affinis, or U. quadrifasciata, visit Cornell University's Bio-control website here and here.
None of these agents have been recovered from the Green Mountain site.
For more information on Bio-control of Diffuse Knapweed visit:
Arapaho County, Colorado- Using Beneficial Insects to Control Diffuse Knapweed (PDF File, 7 pages)
Invasive.org- Biology and Biological Control of Knapweed