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Knotweed injection device

Discussion in 'Pesticide & Herbicide Application' started by lakesregionscapes, Oct 16, 2017.

  1. lakesregionscapes

    lakesregionscapes LawnSite Member
    Messages: 147

    Hi Everyone,
    I did a quick search in the forums, but didn't find this in the first couple of tries, and keep getting sidetracked.
    Dealing with an awkward patch of knotweed in the intersection of several fences at the corner of 3 properties, I'm interested in trying stem injection, but all I can find are ads for various, somewhat sophisticated injection systems... Anyone have a simple solution (generic kitchen basting syringe for example)? Also trying to determine whether every last cane needs to be injected, or half a dozen per clump suffice to wipe out the root system? Most of the patch has been kept down under a couple of feet high, and can be sprayed, but the stuff in the fence is several feet above my head.
    I'm planning on glyphosate, but I recall a seminar a few years back where they found although glyphosate worked well initially the regrowth was pretty bad a year out, whereas 2,4-D had much better long term outcome: any thoughts?
  2. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 15,095

    hort101 likes this.
  3. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 15,095

    Not much experience on my part.
    Turkey baster? Why not? Use a battery operated drill to make quarter inch holes in the stems. Once they are cut down--try drilling vertical holes in the stumps and fill with herbicide. Use a hand sprayer.
    I can only suggest you spray it early and often. A three way herbicide is my favorite. Smash the old dead canes down during the winter. In the spring, try to never let it get more than 6 inches tall before you mow or spray with herbicide again. Try to smash it down, smooth the soil and plant a competitive grass so it is mowable. Try not to let pieces of the plant fly out from the mower and start new sprouts--don't mow when its damp so new shoots can root.
    If you cover it with a tarp--you can exclude light. Use a camo tarp--barely visible from a distance.

    Try to lasso the big rhizomes or roots with a steel cable noose. Give a big pull with a tractor or pickup. Do this when the soil is very moist and soft. The roots may break, but keep digging and pulling until you get most of the big roots out.
  4. BigJlittleC

    BigJlittleC LawnSite Gold Member
    from Chicago
    Messages: 3,635

    Japanese Knotweed I have treated with gly+imazapyr. What I did was crack the shoot and then used an old taxidermy needle. I did every stalk. Got a complete kill. Treatment was done last fall with a follow up this spring. The spring follow up was just a over the top application of gly+imazapyr. Checked the site a few weeks and still clear.
    Wye Oak Tree, On a call and hort101 like this.
  5. lakesregionscapes

    lakesregionscapes LawnSite Member
    Messages: 147

    Since I am 5'4" I figured "over my head" pretty much covered the Japanese part - which mostly seems to stop around 6-7 ft around here.
    It is growing in gravel and through a broken wood stockade fence/cyclone fence - The accessible stuff has been mowed all summer.
    I think BigjlittleC has basically what I had in mind; the needle pierces without having to spend hours hacking away, and the 2ml of concentrate per stem (read that one somewhere, but couldn't find it anymore) - one treated node per stalk does the trick - gets sucked down in. Since it is only around 30ft of fence line it is manageable, in theory.
    I will give it a shot, and follow up with the results here - sometime next spring...
    Thank you!

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