Sheridan County Weed and Pest to spray for invasive grass along I 90 – WYDOT to temporarily close I 90 to accommodate aerial spraying

Sheridan, Wyo - Sheridan County Weed and Pest (SCWP) has asked the Wyoming Department of Transportation (WYDOT) for assistance in controlling the spread of invasive grasses ventenata and medusahead, which are present along I-90 southeast of the Montana state line.

Coordination between SCWP, WYDOT, the Montana Department of Transportation (MDT), the Wyoming Highway Patrol, and others has been ongoing since March of 2024.

The closureis scheduled for Monday, October 7, 2024 - weather dependent, with Tuesday, October 8 as an alternative date if weather aborts the flight. The closure will begin at 7:00 a.m. and will open once spraying is complete - an estimated eight hours. Winds will be the determining factor.

A very specific traffic plan outlining timing and detours has been established to manage the closure of I-90 between the Wyola, Montana Interchange, and Acme, Wyoming.

A twelve-foot width restriction will be in place.

WYDOT and MDT will close I-90 at the Wyola, MT Exit 544 and detour eastbound traffic to MT451 and WYO345 through Parkman and Ranchester to the Acme Interchange at Exit 14. I-90 westbound traffic will be detoured to WYO 345 at Exit 14 to Exit 544 in Montana.

All exits along I-90 within the closure area, including all county and private roads, will be closed to traffic.

Due to the narrow right-of-way along WYO 345 between Ranchester and Acme, traffic may encounter a 15-minute delay while spraying is conducted in that area.

Residents of the Parkman, Dayton, Ranchester, Wyola, and Aberdeen communities are asked to plan their morning commute accordingly, realizing there will be detours and potential delays.

Ventenata and medusahead are extremely damaging invasive species that choke out desirable grasses and can significantly decrease land value. Livestock and wildlife will not graze ventenata or medusahead and they can drastically increase wildfire risk. Both invasive grasses were first confirmed in Wyoming in 2016 and are native to southern Europe and northern Africa.

SCWP has been involved in over 150,000 acres of invasive grass treatments to date. Ventenata and medusahead have been successfully contained in Sheridan, Johnson, and Campbell counties. To continue holding the line, one of the top priorities is controlling these invasive grasses within transportation corridors.

Interstate 90 has a severe infestation of ventenata and medusahead in the right-of-way, which serves as a seed source for nearby populations and significantly increases the risk of seed spread throughout the state.

SCWP will be applying an herbicide utilizing aerial spraying. Aerial application has proven to be the most effective method of applying this herbicide. To apply the herbicide, helicopters need to fly at an altitude of 30 feet above ground level and cannot make applications in proximity to live traffic.

Application by ground spraying equipment is less effective due to the precise and uniform dispersal of herbicide required.

MDT will participate and herbicide application will take place on a two-mile section north of the state line.

All total, 840 acres of right of way in Wyoming and 97 acres of right of way in Montana will be treated.

SCWP will use two herbicides containing indaziflam and imazapic. The safety of both herbicides has been thoroughly investigated prior to EPA approval. Both herbicides are approved by the EPA for use in areas grazed by livestock with no restrictions on grazing following application.

There has also been strong support for ventenata control at the state level, with Governor Mark Gordon requesting $20 million be allocated by the legislature to fund invasive annual grass treatments.

Medusahead and Ventenata growing in the right of way along I-90 in Sheridan County.

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