Herbicide only way to kill knotweed, says contractor

  • Jul. 21, 2010 2:00 p.m.

There’s no green light yet to kill invasive Japanese knotweed plants on the islands with herbicide, but invasive plant contractor Keith Alexander says he believes this will be the only way to deal with the dangerously destructive weed. “It’s the only solution I’ve seen that works,” said Mr. Alexander, who has been trying to control the introduced plant with salt water, without success. “That stuff (Japanese knotweed) is ceaseless, it will not stop.” The herbicide that Mr. Alexander believes would work is glyphosate, the active ingredient in herbicides like Round-up. Based on experience in other communities, he said it is possible to kill the Japanese knotweed by injecting the stems with glyphosate. This method has been used in Washington State and in other parts of BC. But before he can use glyphosate here, he needs the permission of the Council of the Haida Nation, and he must take a course and get a permit. Japanese knotweed is extremely strong and can crack pavement and foundations. It is particularly destructive in stream banks. While many other plants stabilize stream banks, the knotweed instead erodes the bank, eventually destroying the stream. Mr. Alexander told the islands protocol community meeting last month that Japanese knotweed has not yet invaded stream systems on Haida Gwaii, but it is only a matter of time unless something is done. “We have a golden opportunity here now,” he said, before it spreads further. The plant is already found in every community on the islands. Mr. Alexander said that a homeowner in Masset recently got a backhoe in to dig out her entire property, then sifted through the dirt before replacing it, to ensure the knotweed wouldn’t come back. Simply cutting down the plant or digging it up will not kill it, he said, as its roots can extend several metres under the earth. Meanwhile, Mr. Alexander is waiting for the green light from the Council of the Haida Nation to use glyphosate. If he gets permission, he said he plans to apply it on a test area first, such as the skateboard park area of Queen Charlotte, and see how it works.