Weber County 2020-2021
In the summer season of 2020-2021, the USDA Sage Grouse Grant provided for the treatment of approximately 2,258 acres of knapweed, Canada thistle, musk thistle, and dyer’s woad infested forests and rangelands. The project spanned four large private ownerships as well as small amounts of USFS lands that total more than 16,000 acres. Approximately 35 miles of unimproved roads and trails across all ownerships were monitored and treated for weed infestations. Numerous new or undiscovered weed infestations were identified and treated during this project, which originally targeted only 195 acres of known weeds.
Herbicide: Personnel from the Utah Division of Forestry, Fire, and State Lands in cooperation with private landowners and local county employees sprayed approximately 2,258 acres across the four properties from June 2020 to July in 2021. Milestone was used on areas with spotted knapweed or Canada thistle, while dyer’s woad and musk thistle infestations were sprayed with primarily Escort and Weedmaster. Personnel employed ATVs, UTVs, backpack sprayers, and contract helicopters to apply herbicide. Most of the treatments involved spot spraying with minimal boom spraying necessary. Private landowners provided significant contributions with multiple spray days and assistance with spraying efforts. (At left: Worker uses backpack sprayer to treat weeds in less accessible areas.)
Biocontrol: Toadflax weevils (Mecinus janthinus) were collected and released in 10 locations, totaling more than 5,500 insects. Approximately 11,000 knapweed seed weevils (Larinus minutus) were released in 10 locations. Canada thistle flies (Urophoroa cardui) were released in 7 locations for a total of 1,400 insects. And four releases of dyer’s woad rust (Puccinia thlaspeos) were made in 4 different locations. All releases were done in partnership with the Utah Weed Supervisors’ biocontrol contractor. Good release sites have become more difficult to find due to treatment efforts removing forage for potential insects. (At right, biocontrol specialist, Amber Mendenhall monitors and re-releases biocontrol for dyer’s woad.)
Challenges and Successes
- With more than 2,258 acres receiving some variation of treatment, many areas were only monitored or treated on a single instance rather than included in follow-up efforts. Overall, most areas were treated multiple times throughout the summer and well before plant maturity.
- Approximately 60 private landowners and cooperators turned out for our spring spray days to learn about weed control and to implement treatments throughout the project area.
- Overall, the project was quite successful and many areas were sprayed while target weeds were in the rosette stage. Herbicides were very effective and spot spraying in the fall was very minimal in areas properly treated in the spring.
- Although the knapweed population has been significantly controlled during this effort and greatly reduced, various populations of lower priority weeds such as dyer’s woad were able to move into more inaccessible areas that would require a massive backpack spraying effort to fully control.
- Aging equipment with constant mechanical issues reduced efficiency and productivity on a number of days.