When properly applied, Carbaryl is 99-100% effective at protecting trees for the first year following application. It is mixed with water and applied with a high-powered, truck mounted sprayer to the bark of the tree. To maximize effectiveness, the chemical will not be sprayed on rainy or windy days and will not be used near open water or wetland areas.
The Forest is planning to combine the use of Carbaryl with Verbenone, a pheromone, which communicates via smell with the beetles and discourages them from attacking trees. All treatment areas will be closed approx. 1-2 days during spray operations. Sight closures will be posted at all affected areas and on the Bitterroot National Forest website at www.fs.usda.gov/bitterroot. See attached list of proposed treatment sites/dates. All spraying will take place during weekdays. No spraying or closures will occur on weekends.
All campgrounds at Lake Como (Lower Como, Three Frogs, Three Sisters Group Site, Rock Creek Horse Camp) and some of the day use areas (Interpretative Trailhead, Rock Creek Horse Trail, Wood’s Cabin parking area) will be closed next Monday afternoon through Wednesday. The boat launch and beach area will remain open.
The purpose of protecting trees in selected high-value sites is to maintain aesthetic quality and recreation value, and also reduce public safety hazards. To be effective, the spraying must occur prior to the beetle’s annual dispersal flight which typically begins in July.
The Bitterroot National Forest is experiencing increasing tree mortality from the mountain pine beetle that is present at epidemic levels over sections of the Northern Region. Last year, the Forest sprayed more than 2,100 susceptible, large ponderosa pine trees with Carbaryl. Hazardous and infested trees were also removed from a dozen popular campgrounds on the Sula and West Fork Ranger Districts along with thinning 300 acres at the Lost Trail ski area.
Location (CG= Campground) District Estimated # of Trees Spray Dates
Rombo CG West Fork 328 June 17
Alta CG West Fork 183 June 17
Lake Como Darby 1,148 June 18-19
Indian Trees CG Sula 74 June 20
Spring Gulch CG Sula 42 June 20
Trapper Creek JC Darby 25 June 20