Rhizome Injections of Herbicide for Japanese Knotweed – Testing New Injector Prototype

We are testing prototypes of a new rhizome injection system for use on plants such as Japanese knotweed (Fallopia japonica).

We have done preliminary tests with the rhizome injector.  A key aspect of the system is that aerial shoots do not have to be

FIG. 1 - Injection through hollow of dead Japanese knotweed shoot into rhizome

living in order to make an injection. (as this injection in winter shows!)  The injection is into the “green node” which is underground in the rhizome.

FIG. 2 - Cross-section of Japanese knotweed rhizome

 We have had encouraging preliminary results but need to have more rigorous testing especially with outside experts.  Potential advantages of the method include:

  1. injections could be made when the aerial shoots are dead – lessening worries about disposal of living plant parts;
  2. injections are directly into the rhizome – the part of the plant that needs to be killed for long-term success;
  3. amounts of herbicide used can potentially be less – We have thus far used approximately 2 ml per plant (Aquamaster (54% ai glyphosate diluted slightly with 0.15% colorant);
  4. injections could be made at times of the year that are less busy; and
  5. it may be possible (not confirmed) that fewer aerial shoots can be treated if injection is deep enough into the rhizome and herbicide then translocates to a greater number of shoots.

As of January 30, 2012, we are seeking six testers who have:

  1. treated Japanese knotweed before;
  2. used injection and foliar methods;
  3. access to test areas with mature Japanese knotweed stands;
  4. the ability to make at least 3 applications at different times of the year (including spring (before aerial shoots sprout), late summer, and late fall (after die-back of aerial shoots); and
  5. the ability to complete a short test summary with photos.

There will be no cost to the testers and testers can keep the prototype.  If you are interested in finding out more, please contact me at john at greenshootsonline dot com.


  1. dave w

    i have a small infestation (at the moment) of knotweed and have drilled into the rhizomes with an 1/8 drill bit and injected neat round up into the holes with the pipette supplied. the plants certainly are not taking kindly to this treatment and are dying back and producing no new shoots as of yet!!!!!! the rhizomes seem to be rotting so i am forever hopeful!!

  2. Andrew Karleigh

    Just wondering how this is working so far this year. I have a few patches of Japanese Knotweed in the county that I am trying to get some control over and at least one of the property owners would probably like to use this over the cut and treat method due steep embankement where it is growing.

    I know that the one patch that was cut and sprayed last fall showed stress this spring and we cut it once this summer with the hopes of cutting and spraying it this fall.

    • johnlampe

      So far, it is working. We are doing another round of testing – late summer and into the fall and even early winter. We will post results as they come in.

  3. Ken Sanderson

    I’m interested in your injection prototype. We have a large infestation on our property. Never knew what it was nor were told when we purchased our land. It is taking over more every year. I have done lots of research on the plant and I like your method best of all. I have not treated any yet but would like to start. Please email me. Would like to talk more. I have enough of the weed to do many different test sites. I’m on the coast of BC Canada where it seems to be popping up in lots more places every year. I could really use your help. Thank you.
    Ken Sanderson

  4. J McHugh

    Hi! Just wondering if there is any update? We are contemplating rhizome injection of invasive phragmites in our marsh. Thanks!

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