Spotted Knapweed
Biological Control Agents
This weed has been present in Fremont County for over 50 years, but the infestations are still very limited. While the Weed & Pest crews treat this plant very aggressively, we have introduced six species of insects on spotted knapweed in an effort to catch the plants that are missed.
In the mid 1990's the insects released included: the lesser knapweed flower weevil, Larinus minutus, and the green clearwing fly, Terellia virens.
Larinus minutus has established in areas south of Lander with populations high enough for limited collection and redistribution.
For more specific information about Larinus minutus, or Terellia virens, visit Cornell University's Bio-control website here and here.
In 2005 a large infestation of spotted knapweed was discovered in a remote, rough area of the Wind River Indian Reservation that had been burned in 2000. Large releases of Larinus minutus, and the knapweed root weevil, Cyphocleonus achates, were made in the area.
For more specific information about Cyphocleonus achates, visit Cornell University's Bio-control website.
Additional release of the spotted knapweed seed head moth, Metzneria paucipunctella, Urophora affinis, and Urophora quadrifasciata were also made.
For more specific information about Metzneria paucipunctella, Urophora affinis, or U. quadrifasciata, visit Cornell University's Bio-control website here, here, and here.
For more information on Bio-control of Spotted Knapweed visit:
Bio-Control.com- Knapweed Control Agents
Invasive.org- Biology and Biological Control of Knapweed and more info on Spotted Knapweed Control
Wisconsin Dept. of Natural Resources- Spotted Knapweed Factsheet (PDF)