Control of knotweed and other invasive species and experiences restoring native species in the Pacific Northwest US - Spring 2006 By Roberta Davenport via the Native Plants Journal
That was an interesting article, I was an intern last summer for a knotweed control project in Lincoln County Oregon. What a mess... the last two river miles of the Yachats were inundated (walls) by Japanese knotweed. I felt strange applying herbicide but at the same time, I don't want to see our watersheds any more degraded.
Wow, that sure was a lot of work just to kill Knotweed. Glyphosate will knock back this weed somewhat, but is not the most effective chemical in the long run. It is most effective when applied in the fall. Although I do understand the sensitivity of the area being treated. Commercially sold Glyphosate comes with an AI of 365gms/L. And should never be mixed more than 2% for optimum control of foliar applications. The 5 and 8% mixtures they used may just burnt the foliage and didn't translocate properly, could be why they needed so many re-applications. They also mention the use of Garlon4, (Glyphosate) in BC I believe it is only registered for use for BC Hydro, which I have used while working for them. And is not to be used near water ways. 21 years in the vegetation control business, I have dealt with a lot of Knotweed. For permanent control mixing Grazon with Amitrol-T is the key. Do not try this at home. Jim.
The veg control projects I am familiar with do not usually have funding beyond season one sometimes to season two. Funds get pulled grants go away etc. That is here in the US so that is all I am speaking for. I have seen knotweed that has taken over a patch gone within two years and not present upon survey the third. For a home owner to tackle this plant I think it is possible, but with much persistence, requiring careful inspection and diligence in treatment.
Someone who's land we were on last summer asked us the same question, they were from one of the lake states and they had heard of it working there (not on a stream system, but who knows), the nature conservancy brochure says that diligent hacking can work as well as long as you are not spreading the stuff around your yard)
At Jericho Park, we've been testing several methods of controlling (and hopefully eliminating!) Japanese knotweed. After two years, we're seeing some control, but no elimination. We're seeking permission to do a trial using stem-injected glyphosate -- considered the most effective way of eliminating knotweed's reign of terror. Oh, and just in case you were wondering how bad knotweed can get, consider this: In London, organizers of the 2012 Olympics discovered that the land they were going to build a velodrome and an aquatic centre on were infested with Japanese knotweed. Because it could undermine stadium walls and crack concrete concourses, it all needed to be removed -- at a cost of £70 million. (For the Times online story, go to www.timesonline.co.uk/tol/sport/london_2012/article1563967.ece)
Has triclopyr been tried and or in combination with glyphosate? I understand it has a greater penetration in the root of the plant than tradtional glyphosate. Bob
Here is the link on trials of different chemicals and their combination. Looks like Glyphosate is the way to go at 40 % concentration at the rate of 1 gallon per acre, less is not effective, and more is wasteful, expensive. http://www.tbnep.org/docs/invasives/knotweed-guidelines.pdf For smaller infestations stem injections seem to work, check Rodeo or AquaMaster for near the water injections. Best wishes,
I have been working with Japanese Knotweed for a long time now and I have developed techniques to kill it in one year, this can even be done in some cases using glyphosate and stem injection http://www.ecocontrol.co.uk
"We're seeking permission to do a trial using stem-injected glyphosate -- considered the most effective way of eliminating knotweed's reign of terror." Perhaps I am misundertanding but glyphosphate needs to be taken up by the plant system to be effective? Don't knotweeds have hollow stems and simply fill the hollow? I know of someone who tried to control bamboo with Roundup but poured the herbicide into the stem instead of applying the herbcide to the cut and didn't understand why the bamboo still lived.
Has anyone tried spraying them with vinegar? It was the only thing I used that knocked down some patches of lamium, which after that were readily controlled by pulling out any new sprouts, of which there were very few.
Sadly, the link to the article is dead. I have had some success digging the roots out, though, if you miss and split a root in two whatever you leave will send a new shoot up later.
