Questions and answers about the homeowner products for protecting individual ash trees

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Q. Isn't it better to drench under the drip-line of a tree instead of around the base of the trunk?
A. Research tests over the last three years have shown that a basal soil drench (around the base of the trunk) works as well or better than soil injections or soil drenches made evenly within the drip-line. It has never been a good strategy to only drench at the drip-line.

Q. We live in Mason County near Ludington State Park where EAB has been found. We have some ash trees in our yard that we would like to protect with insecticides. Should we start treating them this year?
A. I suggest starting treatments with the imidacloprid basal drench as soon as EAB has been found in your county because it works best when started with a healthy tree. You have the best chance of success if you start this year, as it may be year or two before your trees become infested. The decision of whether or not to treat with an insecticides depends on the annual treatment cost (drenches will cost $25 for a 10" dbh tree, $50 for a 20" dbh tree), the replacement cost, and how much you value the tree.

Q. Our soil is very moist from all the rain. Is it too wet to use the soil drench?
A. Avoid using the imidacloprid soil drench if there is standing water under the tree. Drenching when the soil is moist is okay, except just before a heavy rain. Drenching moist soil may even be helpful for moving the insecticide into the root zone. Movement of imidacloprid below the roots and deeper into the soil or run-off is very unlikely unless a heavy rain immediately follows a drench to saturated soil, or unless a heavy rain follows a drench to extremely sandy soil.

Q. We live in Flint, Michigan. Some ash trees down the street are nearly dead from EAB. Should we use both the drench and the implants?
A. As long as your trees still have a full canopy of leaves this spring and look relatively healthy, you have a good chance of successfully protecting them if you use both the drench and the implants for one or two years, then continue with just the drench each year, after that.

Q. What other trees and insects is the basal drench useful for?
A. I don't recommend using any insecticide unless the tree or shrub is seriously compromised by the insect attack. The imidacloprid basal soil drench has also been used successfully for bronze birch borer on European white birch (no need to treat native paper birch trees), birch leafminer on birch trees, hawthorne leafminer, honeylocust plant bug, and some aphids. It does not work well for spider mites or caterpillar pests.

Active ingredient
Tree and shrub
Basal drench
October to early June
Insect Control
0 0
ACECAP implants
Implant into trunk
April and May
Bonide Bullets

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