Located just across the Columbia River from Portland, Ore., historic Clark County, Wash., attracts visitors who enjoy open spaces. But there are some visitors for whom the county would rather not play host: knapweed, poison hemlock, and butterfly bush, to name just a few.
Left unchecked, invasive plants transform an ecosystem by crowding out native species and the animals that depend on them for food, shelter, and habitat. Noxious weeds also poison people and livestock and create fire hazards. Which is why Philip Burgess, director of the Clark County Weed Management Division, has enlisted an entire community in the state's war on weeds.
In addition to controlling noxious weeds in accordance with state law, Burgess' 10-person crew is responsible for controlling listed weeds in state- and county-owned areas as well as re-establishment areas: the 10,900 acres of surface water, parks, and roadsides on the county's 1,325 lane miles.
But he needs more than a handful of employees to face off against about 10 different species of invasive plants. So the weed management division set up a public education program in 1992 to inform private property owners about the importance of weed control.
“We don't want invasives going back and forth from the roadside areas to adjacent landowners' properties,” Burgess explains.
As part of the public education program, county weed management representatives conduct two large outreach events each year, connecting with about 5,000 people including horticulture students, horse groups, small farm owners, and watershed stewards: One takes place during the spring and one at the Clark County Fair in the fall. The division also conducts a four-hour seminar each spring to inform mower and sprayer contractors about newer technologies and best management practices.
In other locales, landowners are usually concerned when they see herbicides being applied near their property. But thanks to the outreach program, this is rarely the case in Clark County, where property owners are told in advance about the benefits of herbicides. As a result, “some of the landowners are interested in spraying their own land with the same herbicides we're using,” Burgess says.
Burgess and his team members also evaluate the correct timing in which to apply herbicides to get the most efficacy possible. And while only Clark County employees can apply herbicides on county lands, the department shares this information with the public to ensure proper use on private lands. “We have found that people, although interested in controlling weeds, often don't understand the need for the correct herbicide use and timing,” he says. “We want to make sure they aren't wasting their time and money or getting sub-par results.”
One of the most important parts of the program is the volunteers who help spread the word about invasive species. Eight men and women licensed by the Washington Department of Agriculture as herbicide applicators “help us reach people in a way that we can't do on our own with the limited resources we have,” Burgess says. “They keep greenhouses of invasive species that we display at our outreach events, to help landowners identify what weeds are on their properties.”
When land has been overtaken by weeds that are required by state law to be eradicated, the volunteers often help remove the plants by hand.
Another reason residents accept the use of herbicides is the county's emphasis on finding safe solutions. The “Green Team” — a cross-functional team of county staff that oversees environmental stewardship efforts — consults with county department users and technical experts to establish environmental criteria and evaluate herbicides based on the potential for groundwater and surface water contamination. The team also trains county employees and applicators on safety practices.
At least one herbicide — Milestone VM from Dow AgroSciences LLC — that the division relies on is registered under the EPA's Reduced Risk Pesticide Initiative. “It's been a real benefit for us to use herbicides with low environmental impact,” says Burgess.
Another requirement for an herbicide is its effectiveness.
“It's important that we get more than just a burndown of target weeds,” Burgess says. “[With herbicides] Some invasives aren't even coming back the next growing season, which has reduced our costs. Grasses have grown in nicely, and we haven't had any problems with brownout. Perhaps most important, the surrounding landowners see the end results.”
Grants from the state agriculture department help the county eliminate early infestations of noxious weeds, such as yellow flag iris and garlic mustard. Public education also helps the county financially by enlisting the cooperation of residents in the quest to rid land of dangerous plants.
When the above steps aren't enough to control an invasive species, state law and Clark County code makes landowners responsible for controlling the spread of noxious weeds on their property. To enforce the law, Clark County's Weed Management Division established a notification program in 1990.