Acres Treated (project completed on July 18, 2000):
Eagle: 10,378 ac
Imnaha: 7,845 ac
Mill Creek: 2,263 ac
Pine: 15,204 ac
Spangler: 3,912 ac
Total Treated: 39,602 ac ac
(dropped from treatment: Lookout, Pomeroy)
Starting in the mid- to late 1990s, Douglas-fir tussock moth (DFTM) populations rose for several years east of the Cascades in Oregon and Washington. As described in the Final Environmental Impact Statement, land managers identified specific areas where heavy defoliation by tussock moth would likely cause unacceptable impacts on wildlife, watershed, recreation, and other resources.
Two Records of Decisions were issued: the first Record of Decision (ROD) covered the Colville, Wallowa-Whitman, Ochoco, Malheur, Fremont, and most of the Umatilla National Forests, and the second ROD covered the Wenatchee, Okanogan, Winema, and a township on the Umatilla National Forests. The RODs stated that areas with high tussock moth populations may be treated with either TM-BioControl (a naturally occuring virus that affects only DFTM and two other western tussock moth species) or Bacillus thuringiensis var. kurstaki (a bacteria that is less species specific and can affect more of the moth and butterfly species when eaten). The RODs further stipulated that TM-BioControl would be used first until the supply was depleted.
Fall 1999 surveys indicated potentially high tussock moth populations on ~80,000 acres of Areas of Concern on the Umatilla and Wallowa-Whitman National Forests. Seven analysis units were initially identified. Portions of some analysis units were dropped from the proposed treatments where additional sampling in May and June, 2000, indicated non-outbreak levels of tussock moth populations. Treatment began on June 15 and was completed on July 18, 2000. Only TM-BioControl was used in 2000. Post-treatment monitoring of tussock moth population densities, virus infection levels, and defoliation in 2000 has been summarized.
Content on this page last updated on January 16, 2001
webpage was reformatted on July 11, 2005
This webpage was last updated on May 12, 2008.