Launch Slideshow

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The war against weeds

The war against weeds

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    They may look pretty, but invasive plants creep along roadside rights of way and become pests for adjacent landowners. With Clark County's community outreach program, landowners are more informed about noxious species. Photos: Clark County, Wash.,

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    This poorly maintained Zone 1 area shows vegetation growing right to the road edge, allowing water and other materials — in this case, mud — to accumulate. Bareground treatments that remove all vegetative growth prevent water from building up on road surfaces. Photo: Clark County, Wash.

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    Philip Burgess, director of the Clark County Weed Management Division, Wash., injects a stem of knotweed with glyphosate to keep the invasive species from reproducing.

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    Clark County utilizes Washington Department of Agriculture grants to fund control methods for Japanese knotweed, seen here along the Washougal River corridor in Clark County.

“We send out an initial letter if we see that a noxious weed is on a landowner's property, and then a violation letter if the noxious weed has not been controlled,” Burgess says.

The notices include color photos of the noxious weed or weeds and instructions on what to do next, along with a list of mowing contractors and licensed herbicide applicators. In most cases, landowners can mow, cut, and apply legal herbicides to keep noxious weeds and other vegetation in check.

Landowners who don't comply face misdemeanor charges and fines, possibly leading to liens on their properties, while the division can obtain search and abate warrants to enter the properties and have contractors control the weeds at landowners' expense.

As for the public education program, Burgess feels that the more than 15 years' worth of education and outreach has generated a greater sense of understanding by landowners. With diligent effort exerted over the years to come, the department is confident it can put a choke-hold on noxious weeds.

— Stewart is a vegetation management specialist with Dow AgroSciences and is located in Albany, Ore.

In the zone

Washington State's Clark County has a three-tier system for controlling the spread of controlling spread of weeds along roads. “Seeds travel well via vehicle tires, so we emphasize all three zones to help prevent their spread,” says Weed Management Division Director Phillip Burgess.

Zone 1: This zone is the 12 inches of soil that abuts the road pavement. A bareground treatment of RoundUp Pro herbicide from Monsanto Co. is applied 10 to 12 inches from the pavement edge, providing nonselective control by eliminating all vegetation.

Zone 2: Extends from the bareground area to the backside of the ditch bank, which acts as a biofilter for the area. Milestone VM or Milestone VM Plus herbicides from Dow AgroSciences LLC are applied as spot spray applications to destroy specific species like Canada thistle, wild carrot, tansy ragwort, and garlic mustard without harming other plant species.

Zone 3: The remaining area up to private property receives the same treatment as Zone 2.

Burgess estimates that the budgets for the herbicides in Zones 2 and 3 have decreased by $37,000 from when these areas were treated with broadcast applications that involve spraying a large area indiscriminately. Unlike broadcast applications, with spot treatments no native vegetation is killed and grasses can grow back to replace the weeds.