A phalanx of government agencies say a new test program could bring a breakthrough in fighting off the invasive buffelgrass in rugged terrain.

But the plan to send a herbicide-spraying helicopter into Tucson Mountain Park has some county supervisors concerned about environmental risks to other plants and animals, including people living nearby.

Pima County Natural Resources Parks and Recreation Department, the U.S. Forest Service, the University of Arizona and the city of Tucson are working on the project to evaluate the helicopter application of various amounts of grass killer.

The Forest Service has used the helicopter method before on other invasive plants in other states. This project will help determine whether it will work on buffelgrass, whether it works in rugged Sonoran Desert terrain and what concentration of a grass-formulated type of Roundup can do the trick.

Supervisors’ concerns

County Supervisors Sharon Bronson and Richard Elías raised concerns about the project’s side effects as soon as they found out about it this week.

They’re happy to rid the west-side county park of the invasive grass that crowds out native grasses and fuels wildfires, but they’re nervous about the controls in place to protect plants, animals and people near the site.

Bronson said she wants to know how the herbicide will only target buffelgrass when it’s being sprayed from a helicopter onto a large area with diverse plants, and how the county can be sure the chemicals won’t drift outside the study area.

“Unless we have those assurances, I’m not comfortable proceeding,” she said.

Though several agencies are working on the project, Bronson said she thinks the county could stop it since the county owns Tucson Mountain Park.