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White Rock to tackle knotweed
The City of White Rock is striking back against an invasive plant that has the ability to cause serious damage to infrastructure.
Arborist Aelicia Otto said signage advising of steps being taken to eradicate Japanese knotweed on city property – including in Duprez ravine – is scheduled to go up Monday (Sept. 9), followed by chemical injection of the plants on Tuesday or Wednesday.
The work is part of a "management strategy" developed after damage caused by the plant to the Ironworkers Memorial Bridge and the $3.3-billion Port Mann/Highway 1 expansion project made headlines last summer.
Otto said a product with glyphosphate – the active ingredient in RoundUp – will be injected into the stems of the plant at nearly two dozen sites, including 11 in the ravine, where it is destroying streamside habitat.
Chemical injection is the most effective means of eradicating it, Otto said.
"It's taken into the plant and… in the vascular system, the chemical is moved to all the parts," she said.
And, "there's almost no risk to people because of the application method."
But at least one White Rock resident says any risk is too great.
"This should not be done," said Cal Pawson, describing himself as a horticulturist and former nursery manager.
"They're using a whole lot of pesticide for no reason. It's an easy way out… but I'm not convinced it's the best way to go, especially in a sensitive area."
Pawson is hopeful officials can be convinced to use a less toxic approach to the problem, however, Otto said manual removal of the plant is "almost impossible." Efforts to do just that only exacerbated the problem, she said.
Cost of the upcoming work is $1,900. It will likely need to be repeated next year, given the maturity of some of the plant clusters.
Otto said that compared to other invasive plants that exist in White Rock, Japanese knotweed is the easiest to deal with based on the control method. Silver leaf lamium, by contrast, roots easily and grows fast. Its diameter is too small for stem injection and it can't be sprayed because of the threat to other species.
"In some areas, we won't be able to control it," Otto said.
To help with that and other invasives, the city – working with the Lower Mainland Green Team – holds regular invasive-plant-removal events. The next is to take place in November.
Signage advising of the upcoming work on Japanese knotweed will remain in place for at least 48 hours after the chemical chemical's application. The work is scheduled through Sept. 20.
Anyone with questions may contact Otto at 604-541-2116.