Herbicide mistake
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Issue: June 7, 1999

Herbicide mistake

Question:

Help! I've made the mistake of using Pramitol on my driveway, and now my trees are suffering. Is there an antidote I can apply?

Answer:

Pramitol(TM) is a herbicide with a long period of persistence in the soil. It slowly moves through the soil, especially in our arid New Mexico climate. This persistence and slow leaching are factors we need to consider. As long as the herbicide remains in the soil and active, it can continue to cause dieback and death of your trees, even new trees you may plant nearby.

Because it leaches very slowly through the soil, it is sometimes possible to dig a few inches of soil and dispose of this soil (at an authorized hazardous waste disposal site). It is also possible to rototill activated charcoal into the soil to bind the Pramitol and limit its availability to plants.

In your situation (under the driveway), neither of these are feasible. The alternative left to you may or may not be feasible; that is, to cut the roots of the trees at the edge of the driveway so that they cannot absorb the Pramitol. This is feasible only if the trees are far enough from the driveway that you are not removing too much of the root system and not creating a situation in which the trees may blow over because of root removal. (Roots are essential in supporting the trees in our winds.)

If cutting the roots (by trenching along the edge of the driveway) is possible, then the next step is to prevent roots from redeveloping under the driveway by placing a root barrier at the edge of the trench. This is done by installing a Remay Biobarrier(TM). This is a fabric that has dots of treflan herbicide attached to it. The treflan stops the root growth without being absorbed into the tree and injuring the tree. This will prevent the roots from redeveloping under the driveway and absorbing the residual pramitol.

If the trees are too close to the driveway so that you will be cutting very large roots, it may be that you will need to replace the trees. Wait until it is certain that the trees will die. If you replace the trees, consider installing the root barrier so that the roots of the new trees do not get to the Pramitol which will remain for many years, killing trees whose roots go under the driveway.