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WSU/Pend Oreille Extension introduced the Sense of Place series in 1999, with a focus on local landscape and natural history of Pend Oreille County, Washington. A partnership with the Kalispel Tribe of Indians Natural Resources Department has allowed us to expand this program through EPA funding to include more classes, a newsletter and this website.

Bioagents are Eating Up Dalmatian Toadflax and Diffuse Knapweed

If you have infestations of DalmatianToadflax or Diffuse Knapweed read on…


Dalmatian toadflax is an invasive non-native species that poses a major threat to rangeland health as well as plant and animal diversity. It is a creeping perennial, reproducing by seeds as well as spreading roots. The Quad County/Colville Reservation Bioagent Project began mass redistributions of a stem-boring weevil, Mecinus janthinus, in 2000. This agent has caused declines in Dalmatian toadflax populations since its introduction to British Columbia, Canada. Adults of this insect feed on the foliage of the plant, but the most damage is due to feeding of the immatures within the stems. This agent has been observed to establish at most warm southern slope sites, where it has been released, proving to be effective in the suppression of its host plant.

Another insect proving to be effective in weed suppression is a seed-feeder that attacks knapweeds. Larinus minutus is causing declines in diffuse knapweed infestations in Okanogan, Ferry, and Stevens Counties. This agent will also attack spotted knapweed, the predominant knapweed in Pend Oreille County, but similar reductions of spotted knapweed by this insect have not been observed, possibly due to poor transfer by the agent from diffuse to spotted knapweed. In an attempt to overcome this problem, the Quad County/Colville Reservation Bioagent project will be acquiring Larinus minutus reared on spotted knapweed from Montana through cooperation with the USDA Animal and Plant Health Inspection Service in Spokane. Neither insect appears to reduce the density of knapweed or Dalmatian in colder wetter areas. Therefore manual or herbicide controls are encouraged in these type of sites and along all vehicle corridors

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