Mathews Inc.
Japanese Knotweed
Whitetail Deer
Contributors to this thread:
brunse 14-Aug-21
blue spot 14-Aug-21
blue spot 14-Aug-21
blue spot 14-Aug-21
blue spot 14-Aug-21
DanaC 14-Aug-21
Treefarm 14-Aug-21
wvfarrier 14-Aug-21
blue spot 14-Aug-21
brunse 15-Aug-21
blue spot 15-Aug-21
From: brunse
14-Aug-21
Has anyone had any luck killing extensive patches of knotweed?

I have some I need to clean out. I’m in pennsylvania and have read a fair amount of publications from penn state.

I have a backpack sprayer, round up, bush hog and disc.

I have been considering rhis: I spray it this weekend, mow it next weekend, disc it a few days later…. Then try to get some annuals in the ground before September 1.

I suspect I’ll have residual knotweed next year to treat again so I was assuming annuals would likely be best.

Any suggestions? Do I have a chance to get some useful growth this late in the season? Thanks

From: blue spot
14-Aug-21
I think you should just set your sites on getting rid of the knot weed and then worry about planting something you want.

the first thing you have done right is waiting until it is flowering. Give the plants a good thorough coat of herbicide and then do not touch the plants this year. You want to let the plant take in, translocate the herbicide around the plant to the root system and process the herbicide. Glyphosate functions by starving the plant to death. So you want it to go on functioning and depleting the energy reserves. If you mow it and disk it you will separate the herbicide from the root fragments. Each one of those little fragments is capable of growing a new plant. Knot weed is extremely good at compartmentalizing off damaged or injured portions of its self.

A back pack hand pump sprayer will do ok. Keep your pressure up as you want a fine consistent coat over the entire plant. Both sides of the leaves and as much of the stems as you can get. If your concentrated glyphosate is 41-50% active ingredient mix it so that what you are putting on the plant is 4-5% solution of the concentrate.

I like to remix in my empty concentrate jugs. They are 2.5 gallons or 10 liters. Absolutely get your self a graduated cup or cylinder for batching chemical. Use 100ml of the concentrated herbicide for each percent you want your mix to be. When you are mixing many many small batches consistency and simplicity are important. Lastly, always keep a journal of what and when you applied something as well as the weather conditions etc etc. You will have successes and failures. It is a lot easier to reduce the failures by being able to look back at your journal.

From: blue spot
14-Aug-21

blue spot's embedded Photo
treated with 4% glyphosate applied with a back pack mist blower, early september 2020
blue spot's embedded Photo
treated with 4% glyphosate applied with a back pack mist blower, early september 2020

From: blue spot
14-Aug-21

blue spot's embedded Photo
blue spot's embedded Photo
I took this picture in early july. The lilies were all dried up in last years drought , that is why my nonselective application didn't kill them. Because I was being careful of the clients lawn and neighbors yard I ran the mist blower with caution. I have a little more than normal survival in the middle of the patch. I am going back to treat the remainder of it in the next month or so.

From: blue spot
14-Aug-21

blue spot's embedded Photo
blue spot's embedded Photo
this is a road side I am continuing to treat for the town. The selectmen can't seem to communicate with the road agent not to mow what they want me to kill. I understand they need visibility. here is the growth I treated in september and what it looked like the following year. The stems that had no resprouted from the mowing still had enough energy to sprout the following year.

From: DanaC
14-Aug-21
Good info, Eric. That stuff, along with other invasives, is taking over areas around here. Our club actually got grant money for removing 'Russian olive', bittersweet, etc.

That knotweed grows thick and fast. It's invading the lawn here, my landlord can't kill it fast enough.

From: Treefarm
14-Aug-21
Triclopyr 4 (ester) mixed with a penetrating oil. Vegetable oil, kerosene. Treat it like basal bark application for killing trees. Mix at 15-20% Triclopyr 4. For simplicity, add 24oz Triclopyr to container then top off with 8/10th gallon oil of choice. Spray on stalk (no need to cut) paint on with foam brush. Try to paint around entire stem. Maybe 6” wide band. That will kill it roots and all.

From: wvfarrier
14-Aug-21
Im battling Lesser Celendine because the idiots at the local park planted it for erosion control (insert profanity)

From: blue spot
14-Aug-21
Tree Farm, interesting. A number of years ago I tried doing foliar treatment on Knotweed with Garlon, 5% solution. The plants went limp in less than an hour and I looked like a hero. Next year there were sprouts. Using Garlon would be pretty nice in those spots you don't want to hammer some ones lawn.

I have had good luck killing saplings and treating cut stumps on species where it doesnt pentrate the bark with the concentrated garlon(19%) in basal oil or diesel fuel.

painting it on each stem sounds pretty tedious when you are looking at treating acres of the stuff.

A high percentage of what I treat is subsidized by the NRCS.

From: brunse
15-Aug-21
Thanks for the info. I’ll forget the tilling and planting. I’ll just spray it this week, then follow up spraying the spots I missed in another couple weeks. Then again next year.

I had heard that dissing would spread it I was just hoping it would be unable once it was sprayed with herbicide.

You guys saved me some disappointment I suspect

From: blue spot
15-Aug-21
you could throw some winter rye or something similar that has a high probability of taking with no tilling then you would have something there into the fall. Might not be that accessible or attractive to the animals with the stalks still there but the cost of a bag of rye or winter wheat is pretty minimal

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