MISSOULA, Mont. – In the coming days, forest managers will temporarily close a portion of the
Blue Mountain Recreation Area, including the Disc Golf Course, to conduct about 500 acres of
aerial treatment of noxious weeds. The aerial treatment will occur over the course of one day
using helicopter spraying and will help protect native plant understory, improve wildlife habitat,
and improve overall forest health and aesthetics in the area. Aerial treatment will reduce the
noxious weed infestation levels to a more manageable level and allow for other management
activities to occur in this area in the future.
The temporary closure will include:
• Blue Mountain Recreation Area including all trails within the project area and the main
• Disc Golf Course,
• The first mile of Forest Service Road 365 will be closed from 6 a.m.-7 p.m. on the day of
The treatment will not occur on a weekend and will begin early in the morning to reduce public
impact. The helicopter will fly low, using GPS to precisely apply the herbicide and a drift agent to
prevent unwanted drift. Aerial operations are highly weather dependent and if it becomes too
windy, operations will stop and resume on another day. Aerial spraying is the most efficient,
effective, and safe way to treat this area and keep the infestation from becoming a larger
problem because it reduces application time, treats large and inaccessible areas, and reduces
worker and public exposure to herbicides.
Domesticated animals should not be allowed into the treatment area during or after spraying
until the herbicides are dry. Treatment areas will be safe for recreation after the herbicide has
dried and when it is safe to do so, forest managers will reopen the area for use. During spraying,
employees will be posted at trail entrances to the area.
“We thank the public for their patience and understanding as we work to quickly treat this
area,” said Jen Hensiek, Missoula District Ranger. “Reduction of noxious weeds is important for
maintaining forest health for wildlife, native plants and a positive recreational experience.”
Aminopyralid and imazapic herbicides will be used together to treat more difficult rhizomatous
weeds like leafy spurge, but will also be effective on spotted knapweed, thistles, and tumble
mustard. These herbicides are designed to regulate plant hormones and will not impact wildlife,
and follow-up seeding may need to occur.
The results of this treatment will be restorative and help increase native and desirable grasses,
reduce weeds, and improve aesthetics and wildlife habitat. The chance of weeds spreading from
infested National Forest lands to adjacent private landowners with active weed control
programs will also be reduced.
Background: The Missoula Ranger District has been treating roads and trails in the Blue
Mountain Recreation area for decades using a combination of ground herbicide treatments,
biological controls, and hand-pulling/seed head clipping. Aerially treatment is authorized under
the Big Game Winter Range and Burned Area 2001 EIS and the Lolo Integrated Weed
Management EIS 2007 which allows for comprehensive integrated weed management across
the Lolo National Forest.
If you would like to learn more about the herbicides or effects on human health or natural
resources, labels and Material Safety Data Sheets for these herbicides can be found at