Customer questions are always the best. The Garden Gal, Debbie Cook, can take your questions both on and off the air. You can listen to her every Saturday morning on 580 KIDO from 9am – 10am on the D&B Garden Show. You can also hear previous shows, see all her articles, check her out on Facebook and send her a message at GardenGal.mydbsupply.com.
I read the article in the Statesman 10/18/2013 about the Lilac ash borer and the new Emerald ash borer. I have two large summit ash trees and have had borer and aphid problems in the past and have used Bayer Tree and Shrub liquid systemic treatment with success. I couldn’t help but notice the article said the Lilac ash borer cannot be treated systemically. Last summer I had to cut off a large dead branch that looked rotted in the middle, borer damage? This year I could see more upper branches with sparse leafing. Should I be treating these trees another way?
Thanks for the question. The systemic will work great on the aphids but really does nothing for the lilac/ash borer that is affecting the tree. The dead branches are most likely symptoms of the borer damage.
Unfortunately, the only treatment is a topical spray for that particular ash borer. A spray like the pyrethroid “Eight” will work on this insect. You need to begin spraying the ash about the time the lilacs are blooming (~April) and threat through the end of July. Spray the trunk, larger branches and the crotch areas. Treatment at other times is not effective.
Keep your tree as healthy as possible by watering adequately. Use a large mulch ring around the tree to avoid additional damage to the trunk.
I hope that’s helpful. Good luck with your tree!