The leaders of the Sea to Sky Invasive Species Council (SSISC) don't take the practice of applying chemical herbicides to knock back invasive plant species lightly.
They know the chemicals can be detrimental to the environment. However, the situation with invasive Japanese knotweed in the Squamish area has prompted them to launch a program of chemical application that, if successful, should all but eradicate the pesky plant from the area in four to five years, an official said last week.
This week, crews working for the council were set to begin applying glyphosphate the same agent found in the commercial herbicide Roundup as part of the effort to knock back and eventually eliminate Japanese knotweed, a non-native invasive species that, if left unchecked, can choke out native plant species, devastate streams and wetlands and watercourses and even reduce property values.
Kristina Swerhun, SSISC executive director, on Friday (June 29) said the group carried out some limited glyphospate treatments along Highway 99 last year thanks to funding from the Ministry of Transportation (MOT).
It was only after consultation with Squamish Nation officials who previously had barred the use of chemical herbicides within its territory that the limited 2011 program was allowed to proceed, Swerhun said.
Now, with the nation having agreed to allow it and additional funding from the Ministry of Forests, B.C. Hydro and Fortis B.C., a more far-reaching program of chemical applications on Crown land is set to proceed this year.
That includes applications in the sensitive Squamish Estuary, where past efforts to knock back knotweed through hand removal have proven fruitless.
We never advocate for the use of herbicides and pesticides easily, but Japanese knotweed is so invasive that I think application of chemicals by qualified professionals should be supported, Edith Tobe, a professional biologist and executive director of the Squamish River Watershed Society, said on Monday (July 2).
A little bit of damage to the estuary in the short term is far less of a problem than the long-term damage that would be done by the knotweed if it's allowed to take over.
SSISC officials say removal by hand or machine is expensive and seldom effective over the long term. That's because the plant's roots can spread 20 feet below the ground and the plant can regenerate itself from less than one gram of root material. It's estimated that mechanical removal of the plants would cost on the order of $250,000 per hectare, SSISC officials said in a statement.
Public land from Britannia Beach to the Culliton Creek (Big Orange) Bridge is being targeted this year, Swerhun said. The bridge represents the northernmost extent of large infestations of the plant on public land in the area, she said.
Three different application methods are to be used: stem injection, in which glyphosphate is injected directly into the plant's hollow stem; cut and fill, in which the chemical is injected into the stem after the above-ground portion of the plant has been removed; and foliar spray, in which the herbicide is sprayed from a backpack tank onto the plant's surface.
Swerhun said the latter method usually proves most effective with large infestations, but because it is most likely to harm other nearby plants and waterways, is to be used only on large infestations and avoided within 10 metres of the high water mark of any waterway.
The area bounded by Highway 99, Finch Drive and Loggers Lane is one in which spraying is to take place but under carefully controlled circumstances, she said.
We like that option the least because [the chemical] is not contained, because it's being sprayed, and there's a risk of it going to other plants, she said. But when there's a really large stand, it's actually too big to stem inject, so that's one area where we'll spray.
While all chemical herbicides are harmful to most plants, glyphospate is being used because it's been proven effective against Japanese knotweed, it's less toxic to humans and other animals than other chemicals and its toxicity degrades rapidly in the environment.
The time required for the chemical to dissipate by half ranges from days to a few weeks depending on soil characteristics and climatic conditions, SSISC officials said.
While the largest infestations of the plant are on Crown land south of Culliton Creek, smaller stands also exist in the Whistler and Pemberton areas, some of them on private land, Swerhun said.
It's [chemical removal] generally about 80 per cent effective each year and we're hoping that within four or five years, with constant monitoring and selective treatment, we can see it gone forever, she said. Then it's just a matter of not spreading it intentionally.
For more information, including a schedule of chemical applications, visit www.ssisc.info
