Broadwater County board reports Ventenata, rush skeleton weed detections on I‑90; plans fall surveys and outreach

Broadwater County weed board members said this week that invasive grass species have been found along Interstate 90 on the county’s western edge, and county staff and state transportation crews will conduct follow-up surveys and public outreach.

Board members discussed two recent detections: a plant identified as ventenata and a plant identified as rush skeleton weed in the I‑90 right-of-way just west of the Three Forks exit toward Milligan Canyon. A contractor flagged the locations, and the board said the plants were treated with Tordon before a formal county/state survey could be completed.

The board said Montana Department of Transportation (MDT) personnel and state specialists are participating in follow-up work. A state specialist estimated one plant was about two years old, and MDT staff have been instructed to wash mowers when leaving the I‑90 corridor to avoid spreading seed to other roads. The board said contractor and MDT crews will continue monitoring the corridor and will recheck the sites in the fall.

Why this matters: ventenata and rush skeleton weed are invasive grasses that can establish dense populations and create seed banks that spread along equipment routes. Board members and staff said early detection and coordinated treatment reduce the risk of longer-term infestations and spread to neighboring counties.

Details from the meeting: board members said the ventenata sighting was reported about two weeks before the meeting and the rush skeleton weed about four weeks before the meeting. County staff noted that by the time the county surveyed and marked the site with MDT and state staff, mowing had already occurred in the right-of-way; the contractor had treated the plants with herbicide prior to those mowings.

Speakers discussed outreach steps the county will take if the infestation is more widespread, including educational notices in county newspapers and working with Montana State University extension agents and local extension listservs to reach small-acreage landowners, ranchers and stockyards. The board said extension has broader local lists and can reach owners of small parcels and subdivisions who may not recognize the species and might inadvertently spread seed by mowing.

Board members also noted that the state’s Rush Skeletonweed task force may expand its survey boundaries to include Broadwater County if follow-up finds more than an isolated population. The board agreed to a fall and spring monitoring schedule: county crews will recheck treated areas in the fall, apply additional treatment if needed, and check again in spring for regrowth.

The county emphasized decontamination measures for equipment, ongoing coordination with MDT and state specialists, and targeted education for residents in affected areas.

The board did not take a formal vote on this item; members directed staff to continue monitoring, coordinate with MDT and the state, and prepare outreach materials.