How to Treat Ash Trees

Ash trees are in great danger in the U.S.

Ash trees in North America have been in serious trouble since 2002, when the emerald ash-borer beetle was first discovered munching on the bark of an ash tree in Michigan. These pests have been decimating whole swaths of ash trees ever since, and in ever-growing numbers. The only way to treat an ash tree in danger of succumbing to this bug is to apply insecticide in spring, and before the tree starts to show dying branches.

Things You'll Need

• Tape measure
• Bucket, 5 gallon
• Gloves
• Protective clothing
• Insecticide containing imidacloprid

Instructions

1. Buy enough insecticide to treat all of your ash trees. Be sure to purchase the kind of insecticide marked for trees and shrubs, containing the active ingredient imidacloprid.

2. Run a tape measure around the trunk of each tree to measure its circumference. You will need this measurement to calculate the amount of insecticide to use.

3. Prepare to drench the soil around your ash trees in a ratio of 1 ounce of insecticide for every inch of distance around the trunk. For instance, if the ash trunk's circumference is 26 inches, you will need exactly 26 ounces of insecticide for that tree.

4. Measure the appropriate amount of insecticide for the whole tree into a 5-gallon bucket. Fill with water. Pour the insecticide mix into the ground at the base of the tree. Pour slowly, so that it will soak into the ground, not run off.

5. Wait for the roots to absorb the water and pull the insecticide up into the tree over the next few weeks. You should see evidence of dead ash-borer beetles during that time--or better yet, none at all.

Tips & Warnings

• Emerald ash-borer beetles attack healthy ash trees of all ages and sizes, so treat saplings as well as mature trees.

• Do not apply this method if the tree has already lost more than 20 percent of its canopy. Rather, cut it down immediately and burn it to prevent the infestation from spreading.

• Be sure to wash out buckets or containers used to mix and apply insecticide, especially if you have pets or young children.

References

• Michigan State University: PROTECT ASH TREES AGAINST ASH BORERS BEFORE END OF APRIL
• Iowa State University: As ash borer claims more trees, researcher at ISU works for species survival
• Michigan State University: State officials outline Emerald Ash Borer response plans

Resources

• Wisconsin Dept. of Natural Resources: What You Can Do
• Illinois Government News Network: Gov. Blagojevich proclaims Emerald Ash Borer Awareness Week