"Lavendar" Ash Borwer in Colorado #322670 - Ask Extension


"Lavendar" Ash Borwer in Colorado #322670

Asked May 18, 2016, 11:17 AM EDT

I had someone representing a well-known lawn care business going around our neighborhood in Erie, CO suggesting that we look at treating our tress, not for Emerald Ash Borer, but for a Lavender Ash Borer. Any reality that this bug actually exists. I know full well of the EAB, being employed by Boulder County and having to deal with it here. But a "lavender ash borer" seemed a little new and strange to me.

Weld County Colorado

Expert Response

Never heard of that, but a VERY common borer on ash trees is the Lilac-Ash borer.

Maybe the representative meant Lilac-ash borer.   More info:


Robert Cox Replied May 18, 2016, 12:38 PM EDT

Thanks Robert. She may have said Lilac and I mistook for lavender (thinking of colors – emerald vs. lavender). I’ll check the link. She did point out some very distinct bore holes. I’m thinking of just taking out that ash and replacing it with something else. Do you have any recommendations? It's a street lawn tree, so it fits the profile of one that is primarily susceptible to the LAB. I also have a purple ash I planted farther away from the street next to our driveway that appears to be fairly healthy.

The Question Asker Replied May 18, 2016, 1:24 PM EDT

Drought-stressed ash trees, those with a limited rooting area, or other stresses make that ash more prone to LAB injury.  Autumn Purple ash is very susceptible, especially when stressed in any way.  So be sure to provide it adequate water during the growing season AND during dry warm snowless periods in winter months

The borer exit holes she showed you are almost certainly the handiwork of LAB.

Preventive trunk sprays of the insecticide carbaryl (Sevin and other trade names) or permethrin (several trade names) should be applied mid-April to mid-May.

If you decide to replace the ash tree with another type of tree, consider these; note that every tree has some potential pest problems and disavantages.

Skyline honeylocust  

Japanese tree lilac

Sensation boxelder

Hackberry (many insect galls)

Greenspire Linden (may leaf-scorch in limited rooting areas)

Norway maple - many named varieties

Robert Cox Replied May 18, 2016, 6:12 PM EDT

Thank you Robert. You've been a "tree"-mendous help. (sorry, had to do it....). Have a great day!!

The Question Asker Replied May 19, 2016, 10:10 AM EDT

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