Stem Injection of Invasive Knotweed - Part I of II on Green Shoots Injection System

This video, Part I of II, answers key questions about whether stem injection is the right method for treating your invasive knotweed stand. Part II is at • Stem Injection of Inva... .
0:18 - Herbicide for use with stem injection of knotweed.
0:42 - Stem Injection Advantages.
0:48 - First, the task of injecting is pretty simple.
1:08 - Second, injections are less weather dependent than other treatment methods.
1:52 - Third, Injections are effective even during droughts. In fact, drought seems to enhance the effectiveness of injections.
3:34 - The potential disadvantages of stem injections.
3:37 - First, injections are not well suited for large sites.
4:03 - Second, you can't inject stems under 1/2 inch in diameter.
4:34 - Third, injection uses a lot of herbicide for each injection.
5:21 - Planning the knotweed injection treatment.
5:27 - Consider a map of your treatment site.
6:18 - Figuring out how much herbicide you will need.
8:18 - Buying the materials you will need
8:37 - One other critical thing - knock down the dead knotweed stems from the year before.
9:13 - What time of year should you do your stem injections?

[@SuperFeist]

I bought a stem injector from the UK last fall. Did a combination of injecting the largest stems of my big patch of knotweed and foliar spraying twice with a 2 week break in between. This killed about 90% of the knotweed and it's rewarding to see the area not being taken over by knotweed for the first time in years.

[@GreenShoots]

Combining methods of treatment makes sense in so many situations. In some spots you want more accuracy. In other parts of a stand, you can use a faster method like foliar applications.

[@sethmoking]

I may get an injector next year. Last year was my first year foam spraying. Then this Spring I burned all of the dead stems so that I had a clean patch. This year, there was significantly less growth where I had sprayed, but the patch is so big that when I walk into the middl of it, the leaves are clear above my head and spraying is not really an option. I'm thinking of injecting the stems in the middle of the patch that I can't really spray, and then spraying the perimeter again. One question, I noticed that this year I've got some Frankenweed growing that is clearly knotweed that got sprayed last year. What am I supposed to do with that? I'm thinking of taking some regular roundup spray and just dousing it. The foam doesn't seem like it would make any sense since there are no broad leaves to apply it to. Thoughts?

[@GreenShoots]

The option you describe makes sense. The most important thing with any knotweed stand is getting the most effective herbicide application possible on that portion of the stand you treat. Injection is highly effective. The downside with injection is it uses a lot of herbicide, and there can be residual effects from the herbicide to nearby non-target plants. In the middle of a large stand, this isn’t really a problem. With your method you can move outward from the middle with injection and inward from the perimeter with foam foliar applications. With the foam foliar, you want to do a follow-up treatment as described in this video about two weeks after the first one. I advise this with any foliar treatment because the knotweed canopy protects leaves and green stems lower down. Getting a second dose on these lower green stems is really critical for success.
One thing about the really tall knotweed. We are now offering a spray conversion kit for our Large Dispenser. With this kit, can outfit the dispenser with a streaming nozzle. This will allow you to loft a stream of liquid that can then cascade down like rain onto tall knotweed stems. For a first application this can be effective and very efficient. This stream is much less drift prone than spraying small drops. Just be sure, as mentioned above, to do follow-up application to anything still green.
Finally, you mention the knotweed that came back distorted from your previous herbicide application. The leaves of these deformed knotweed don’t seem to absorb much herbicide. I would just cut them down and then spray foam herbicide on the cut stem or stems.

[@mr.buckles3]

If knotweeds develop large root systems, why not inject into the largest part of the root system? Does this not distribute the herbicide throughout?

[@GreenShoots]

Intuitively that makes sense. I have tried injections into the rhizome and applying herbicide directly to exposed rhizomes. Neither technique has worked well.

[@gemthree483]

I bought the injector system and completed the injecting all stems over Labor Day weekend. I want to wait 2 weeks to them cut and apply the foam application on top of the cut stems. Is this a good idea? I’m hoping that this will get rid most of the knotweed come spring.

[@GreenShoots]

I would not do an additional herbicide application to a knotweed stem that was recently injected (within the last few months). Also, don't cut any of the knotweed stems that you injected until those stems turn completely brown. You want to make sure the nutrients in the green stem help transport the injected herbicide down into the underground rhizome. Cutting may inhibit the transport.

[@YellowStickerGaming]

Great video, except right at the end it was a little unclear. Under what circumstances should one do 2 injection applications -- one in middle of summer, one in fall?

[@GreenShoots]

I am glad you caught this. If you do an injection in mid-summer, you should do another herbicide treatment in the fall. However, it's very likely the fall application will not be with injection. Most of the stems will probably not be sufficiently large (greater than 1/2 inch in diameter) to be injectable.

[@SK-pk3yt]

Very nicely explained.excellent information. Genuine person with no monitory benefit

[@GreenShoots]

Thank you! However, I should point out that my company sells a stem injector. There are others on the market too. Just want to be upfront about that.

[@williaml8474]

Thoughts on adding ammonium sulfate ( ruclips.net/video/akIV-zAt7VQ/видео.htmlsi=FWfl-0dukTQmf4Vf ) to the mix for the foliar application?

[@GreenShoots]

I would definitely do it if the water to be used in the mix is hard. Otherwise, it is probably not necessary. For those who have hard water, they can also use distilled water instead of buying AMS adjuvants.