An article in the Omaha World Herald last week prompted calls to my office about the Emerald Ash Borer (EAB). I wasn’t in the office 10 minutes before I got my first call. The article indicated that EAB had been detected in traps in Council Bluffs and also at Mahoney State Park, between Omaha and Lincoln. While this is not good news, it is still not reason for homeowners with ash trees in northeast Nebraska to panic or start treating their trees... yet.
EAB is a devastating pest to all kinds of true ash trees. It will not attack mountain ash trees which are not related to ash trees despite their name. The bad news is, it will eventually get to this area. The good news is, it isn’t here yet and may not be for several or many years.
On their own, EAB can fly and move up to about 12 miles a year, although the majority will only move two or three miles. That is why we do NOT recommend treating ash trees until it has been confirmed within 15 miles of your ash trees. Current counties under quarantine in Nebraska include Dodge, Washington, Douglas, Sarpy and Cass counties.
It is illegal to move any ash wood products including firewood, nursery stock, ash lumber, wood chips and other ash products out of the quarantined counties. Those materials can be moved within the quarantined area, but not outside of the area.
Currently, the closest areas where EAB has been confirmed is in Missouri Valley, Iowa, in Sioux Falls, South Dakota, as well as in Omaha and northwest Cass County including Mahoney State Park. So you can see, EAB kind of has us surrounded but isn’t close to being within 15 miles of us.
There are two methods to treat trees for EAB, soil drenches and injections into the trunk of a tree. Soil drenches are ineffective on larger trees which leaves injections as your only alternative. The reason to not start treating your trees too early is in parts of the country where EAB has been a problem for years and trees have been treated with injections, it was found that trees started to go into decline after repeated treatments, just from the injury caused by drilling the holes and treating the trees, not from the EAB itself.
So you don’t want to shorten the life of your ash trees with unnecessary treatments for a pest that’s not here. The treatments are not inexpensive, so save the cost of making those treatments until they are needed. The cost of the treatment will vary with the size of the tree being treated. Your money may be better spent purchasing a replacement tree rather than treating an existing tree. Also, I do not recommend removing ash trees that are in good health. It may have several more useful years in your landscape.
What I do encourage people to do now is evaluate the trees in their landscape and decide if they are going to treat or replace those trees when the EAB does get there. A specimen tree in good health and serving a key role in a homeowner’s landscape is a good candidate for treatment.
It may be more advisable to replace an ash tree rather than treating it if the tree is not in good health, has had major damage in the past, or may be showing some dieback now. In many cases, replacement trees can be planted near existing ash trees and allowed to get established while leaving the ash tree in place. You may need to remove some lower branches on the ash tree to allow the replacement to develop.
Then when it becomes necessary to remove the ash tree, you have a head start on a new tree to take its place. When selecting replacement trees, consider well adapted tree species that aren’t as commonly used in landscapes.
That way when the next major problem (i.e. - Dutch Elm Disease, Pine Wilt, Emerald Ash Borer, etc.) for some species of trees occurs, you are less likely to lose those trees. There are a number of good sources for suggestions to replace ash trees including websites for the Nebraska Forest Service and the Nebraska Statewide Arboretum as well as many nurseries.
For more information on EAB including identification and treatment recommendations, contact your local Nebraska Extension office.