County Roadside Vegetation Management Program Changes

Pierce County now uses its own crew to spray; heavy early rains delayed the start date and testing of a new mix of herbicides.


In late May and early June drivers may have noticed wider than usual swaths of dead vegetation along the sides of many Key Peninsula roads. A combination of factors, including unusual early spring rains and changes in the county’s integrated vegetation management program explained the situation, said Jeff Rudolph, environmental biologist with Pierce County Planning and Public Works Department’s Maintenance and Operations Division.

The county has used a variety of herbicides since the 1990s, along with mechanical brush cutting and tree trimming to manage vegetation.

“It’s a safety issue,” Rudolph said. “You need good visibility and a clear zone if someone needs to swerve. And it is important to have proper drainage of water off the road and into a ditch.”

The county had contracted the herbicide program out since 1998 but decided to self-manage in late 2021. That meant training and licensing crews and retrofitting and licensing equipment, with both processes completed this year. No herbicide spraying took place in 2022 as the program transitioned.

The Key Peninsula typically is one of the first areas in the county to be treated, usually starting in early March and ending two weeks later. Brush cutting and tree trimming take place year-round.

Spraying does not take place during heavy rains as a matter of safety. “Any risk goes up if application takes place in wet conditions, if the water table is high or there is flowing water,” Rudolph said.

This year, because of the heavy rainfall, spraying did not begin until the end of April and wasn’t finished until June 7. The combination of a late start and no treatment in 2022 meant that there was more vegetation growth prior to spraying than usual and more dead plants to see once the treatment was completed, Rudolph said.

Roads with moderate to high traffic volume — 131 lane miles or 45% of the 285-mile total on the Key Peninsula — were treated this year.

The county used a new combination of herbicides from the Washington State Department of Transportation, consisting of Roundup Pro, Esplanade 200 SC, Milestone and Escort XP. Rudolph will evaluate its efficacy this summer. It usually changes formulas every three to four years, he said.

The herbicides themselves are approved for use by the state and are degraded by sunlight or the soil microbes over about 30 to 45 days. Toxicity is measured in three levels, with “danger” as the highest, followed by “warning” and finally “caution,” he said. The county uses those at the lowest toxicity.

To assure the safety of the crew the herbicide is pre-mixed. If people or pets are walking along a road the crew comes back another day. Not all areas are sprayed. Stream crossings are marked by green fiberglass posts with salmon insignias and are avoided. The crew, all of whom have had 60 hours of training and passed a state test, know to avoid wetlands, areas with gardens and yards adjacent to the roads, and areas within 60 feet of marine waters or 200 feet of schools.

The county is evaluating the impact of the spraying on pollinators for the first time this year.

Rudolph said they may map out areas they know have bee populations and avoid spraying there, or may try to spray earlier before flowers begin to bloom.

For those who don’t want their land sprayed, the county offers an owner maintenance program. About 90 people in the county participate. 

“As long as the owner can maintain and keep vegetation from encroaching on the roadway, that’s fine with us,” Rudolph said.

Owners can call or apply online and must renew each year. The county provides a sign for the landowner to display. 

For more information, call 253-798-6000 or apply online at