Misconceptions About Treatments

 Several misconceptions surround emerald ash borer (EAB), particularly in regard to treatments. Here are some clarifications on commonly asked questions and issues.

“Doesn’t EAB occur throughout Nebraska?”

As of June 2016, EAB has been found in only a few locations in the state. It is possible that EAB is present elsewhere, but has not been detected. We do have other types of borers that attack ash, such as the similarly named “ash borer” (aka lilac borer or lilac-ash borer), which is unrelated to the emerald ash borer and is not as damaging. With each new county detection of EAB, an announcement will be made by the Nebraska Department of Agriculture, the media will spread the news, and workshops will be held to provide guidance to homeowners.

“When should I begin treatments?”

Treatments for EAB should be considered only when EAB is known to be present within 15 miles of your tree. The 15-mile recommendation strikes a balance between protecting valuable trees and limiting the negative effects of unnecessary treatments. Treating trees outside of the 15-mile zone provides little or no benefit to the trees, yet exposes humans and the environment to pesticides, wastes money and, in the case of trunk injections, causes unjustified tree damage.

“If I treat now I won’t have to worry about EAB later.”

Treatments are not a one-time occurrence. They do not immunize the tree for life. Ash trees to be saved will likely need to be treated every one to two years, depending on the type of treatment. Less frequent treatments may be possible after most of the ash trees in an area have been killed and the EAB population has decreased, but this serious pest will always be with us, and valuable ash trees will always need periodic protection.

“Isn’t it too late to treat after a tree is attacked?”

EAB usually requires a minimum of a few years to kill an otherwise healthy tree. Infested trees can be successfully treated, even those with a fair amount of canopy decline. Beyond about 50 percent decline, however, recovery is less likely. Emerald ash borer (EAB). Photo courtesy of City of Champaign, Illinois The University of Nebraska-Lincoln is an equal opportunity educator and employer.

“Can I treat my trees myself?”

Homeowner-applied treatments are somewhat limited. The most available method involves a soil drench around the trunk, which might not adequately protect large ash trees. In addition, flowering plants growing near the tree can easily pick up the chemical, exposing bees, butterflies and other pollinators to the toxic material. Professional arborists have more options available to them, such as trunk injections, which help limit the effects on non-target organisms.

“What should I know about trunk injections?”

Trunk injections can effectively control pests, but they do have drawbacks. Most are applied by drilling holes into the trunk, which opens up the trunk to insect pests and decay fungi. The drilling may also break through internal barriers within the trunk that have been made to wall off internal decay. This decay may then spread from the inside out through these injection wounds. In addition, the pesticide itself can cause internal damage that may accumulate over years of repeated injections and potentially kill the tree, even if the pest is controlled. If injections are used, trees should not be re-treated until the injection wounds seal over with new tissue. Injection treatments that use small, shallow holes and smaller amounts of product are less damaging.

“Maybe I shouldn’t treat at all.”

The many benefits of trees are well-known: shade, beauty, improved air quality, stormwater regulation, etc. A well-placed tree may be extremely valuable, and some trees may have great historical or sentimental value. If you do not treat, any benefits the ash tree is providing will likely be lost, and the cost of removal could in some cases be very high. But considering the cost, potential damage and varying effectiveness of treatments, it is wise to be very selective when deciding which ash trees to save, if any. The best candidates for treatment are high value trees that are properly sited and in good health. If you decide not to treat, you may want to plant other tree species nearby to replace the ash that will someday be lost. For more information see: FH25-2015: