If you can keep the area mowed for a year or so in a drier climate, it will eventually be the end of them…and it helps if you can get the bigger portions of the stumps and roots. I managed that without any spray, but then we tend to be very dry.
I’ve been spraying a lot of suckers here with 4-5% glyphosate. Looks like they are mostly dead now. Took three spays about a week apart to make them brown and crispy. Time will tell if they come back or not.
My math may be way off… The 41% Glyphosate concentrate I bought suggests 6oz per gallon. I initially mis-read the instructions and used 2oz per gallon. And it killed basically everything I sprayed it on. At the 2oz per gallon rate would that not be about .6%? Making 6oz per gallon be 1.8%? Thanks.
Thank you all for your replies. I will pass this info on to my friends, I am sure it will be a big help. I know they are going to fight suckers from a vacant lot next to theirs. There are some mature TofH over there, and nothing is being done to control them.
Interesting responses to glyphosate too. It doesn’t kill poison ivy or bind weed here, at least not in a one-time application, but it will definitely damage fruit trees if you’re not careful! .
Tordon/Pathway are picloram + 2,4-D. Kills things well - but, I’ve had bad experiences with desirable trees near (within 10 ft) of trees that I did stump treatments on, being damaged… not killed, but it certainly made 'em really sick for a year or two.
Anymore, I won’t use that herbicide if I think the stump to be treated might share rootzone soil with a desirable tree… but ToH might be one that I’d use it on, even in that setting, if all else failed.
Certainly does sound like Picloram could cause some collateral damage:
“Picloram kills or damages annual and perennial broadleaf herbs
and woody plants. It acts as an “auxin mimic” or synthetic
growth hormone that causes uncontrolled and disorganized
growth in susceptible plants. Picloram does not bind strongly
with soil particles and is not degraded rapidly in the
environment, allowing it to be highly mobile and persistent
(half-life of picloram in soils can range from one month to
several years). In soils, picloram is degraded primarily by
microbial metabolism, but it can be degraded by sunlight when
directly exposed in water or on the surface of plants or soil.
Picloram can move off-site through surface or subsurface
runoff and has been found in the groundwater of 11 states.
Picloram may also “leak” out of the roots of treated plants, and
be taken up by nearby, desirable species.”
I’ve read that root-to-root contact between the sprayed Tree of Heaven and nearby trees, and that is what causes the unintended damage. Could be. I know ToH roots go many tens of feet out from the tree, especially in response to injury - just follow the new sprouts along the lateral roots.