Injection gets try with stubborn plants
June 25, 2008 · Updated 5:19 PM
In an approach similar to giving an inoculation, the state DOT is trying a new method of controlling weeds: The agency is injecting weeds rather than spraying them with herbicide.
DOT engineers spent approximately four hours Wednesday injecting the herbicide glyphosate commonly called Aquamaster directly into the hollow stems of Japanese knotweed on portions of an acre of land near Clinton along Highway 525.
Knotweed is a noxious weed that spreads quickly, shading out other native plants and destroying habitat, according to the DOT. If not controlled, it spreads into wetlands and river systems, causing an irreversible loss of habitat for fish and wildlife.
In the past, the DOT has sprayed knotweed on South Whidbey. The use of the spray, however, has been protested because of its potential impact human health, said DOT maintenance manager Ray Williard. After a year-long row between the agency and the Whidbey Island No Spray Network, DOT has been working with local spray opponents to some extent, ceasing roadside spraying in some areas along the islands highways.
The decision to inject the herbicide was made through meetings between DOT officials and Whidbey Islanders, including members of the countys weed control board.
The whole process defined all of our vegetation management activities for the state highways on the islands, Williard said.
The change has several benefits. Injecting the herbicide expected to be 100-percent effective, Willard said. Proof of the sprays ineffectiveness can be seen at the site of Wednesdays injections, where knotweed sprayed with herbicide last year has begun to grow back.
The injection device ensures that the exact amount needed is used, as well.
The largest change, though, may be what injecting herbicide does not do.
It minimizes the chance of any herbicide moving off target, Willard said.
Without knowing a lot about the new technique, WINS responded to the new weed control method with cautious optimism.
WINS president Mark Wahl said the injection method is an improvement over spraying. However, from his groups perspective, a non-toxic approach such as pulling the weeds is preferable.
But knowing how hard it is to control, its probably the best technique for now, Wahl said.
Williard said it will take two to three weeks to see signs of the herbicide working.
DOT crews will reseed the area with grasses after the knotweed is removed.