Yes, white ash is seriously threatened by emerald ash borer, an invasive beetle from northeastern Asia that has killed at least 50 million ash trees in North America. The beetle attacks healthy trees as well as weak ones, so an untreated white ash in an infested area remains at risk.

Why is white ash so vulnerable to an emerald ash borer?

Because the beetle's larvae feed inside the tree, in winding tunnels under the bark that cut off the flow of water and nutrients. Good vigor helps a white ash avoid many common problems, but the adult beetles readily lay eggs on healthy trees too. As the beetle spreads, white ash is now listed as Critically Endangered by the IUCN, the international body that ranks how threatened each species is.

How can an emerald ash borer be spotted on a white ash?

By small D shaped exit holes in the bark, left where adult beetles have chewed their way out. A thinning, declining canopy follows as the tunnels under the bark spread.

What protects a white ash from an emerald ash borer?

A systemic insecticide, one the tree takes up and carries through its own tissues to where the larvae feed. Fertilizer supports general health but does not stop the beetle, as the ash fertilizer guide explains.

To protect a white ash for 12 months from one application, Once A Year Insecticidal Drench w/Merit is applied around the base of the trunk at 1 oz of concentrate for every inch of trunk circumference at chest height, and the roots carry it up into the tree.

Frequently Asked Questions

Is there a way to protect a white ash besides a soil drench?

Yes. Where a soil drench works up through the roots, the Multi Insect Killer Tree Injection Kit deposits insecticide by syringe into shallow holes drilled around the base of the trunk, and treatments early in the growing season are the most successful.

How large a white ash can one bottle of the drench treat?

One with a trunk 32 inches around. A 32 oz bottle covers 32 inches of trunk circumference measured at chest height, so a larger tree needs more than one bottle.

Is white ash more resistant than green ash?

Slightly. White ash shows a little more resistance and, in an infested area, is usually killed only after the green and black ash are gone.

How quickly can the beetle kill the ash in an area?

Within about 10 years. Without control, all the ash in a newly infested area are expected to die in that time.