February 23, 2017
Emerald Ash Borers are No Gem!
Today I wanted to talk about an insect that’s been in the news for over 10 years. The emerald ash borer has the potential to be devastating to ash trees when it gets to our area... but the key word here is WHEN!
Emerald ash borer has not been found in Northeast Nebraska. The nearest it has been confirmed is two locations in Omaha and in the northwest corner of Cass County, about half way between Omaha and Lincoln. This borer has been in the news long enough tree owners are asking if they should start treating, or take the more radical step of removing ash trees. I had someone in my office that wanted to cut down a couple healthy ash trees because of this potential threat. Now I have an ash tree just east of my house and I’m sure some day I may need to remove it if emerald ash borers find it. But I’m not going to cut it down now and give up potentially 10 to 15 years of shade and beauty for a pest that probably will get here some day, but is not here today. And I’m not going to spend money on treatments to treat a pest that is not here.
The recommendation of the Nebraska Forest Service and Nebraska Extension is to wait to begin treatment until emerald ash borer has been confirmed within 15 miles of your ash tree(s). This is the greatest distance adults have been documented to move from an infested tree, but most of the movement has been five miles or less. According to the Nebraska Forest Service, treating trees beyond 15 miles will likely provide little or no benefit to the tree but will result in unnecessary environmental exposure to pesticides and unneeded expenses.
In addition, drilling holes in the trunk to treat a tree will also injure a tree and eventually repeated treatments will cause decline in an ash tree. So it is unwise to start treatments before it is needed. If you have an ash tree, you should know that state and federal agencies are monitoring emerald ash borer infestations and will provide updates on where it is found in Nebraska. Information about it and about when and how to treat ash trees can be monitored on the Nebraska Forest Service website. Go to http://nfs.unl.edu/.
After I tell people to wait, I'm often asked what if emerald ash borer is in the area, but hasn't been found yet. It can take up to five years for this borer to kill a tree. So once it is confirmed, it has likely been in the area for at least a few years. However, unlike pine wilt which killed most of our Scotch pine where the tree must be treated prior to the nematode infesting the tree, ash trees that are already infested with emerald ash borer are still treatable and the tree can be saved if the damage is not too severe. Instead of making pesticide applications likely to be of little benefit, become more informed to help make decisions about emerald ash borer. If you have an ash tree, decide if you are willing to treat the tree on an annual or every other year basis or if you will replace the tree. Valuable trees, such as those providing shade for a home and are in good condition, may be worth the cost of treating. Trees with health or structural issues or those not planted in key locations, may best be replaced rather than treated. For example, if a tree has branch dieback, sparse foliage, or severe trunk injuries, it probably is not worth the expense of treating.
Currently five Nebraska counties, Dodge, Washington, Douglas, Sarpy and Cass are in a quarantined area. Ash materials from these counties including trees, logs, branches, roots, green lumber, hardwood firewood and chips; as well as viable emerald ash borers must not be transported out of these quarantined areas. There are also a lot of other insects that look similar to and can easily be confused with the emerald ash borer. If you have an insect that you think might be emerald ash borer, take it to your local Nebraska Extension office for identification. Images of look-alike insects can also be found on the Nebraska Forest Service website at http://nfs.unl.edu/.
For more information on emerald ash borer or on selecting a replacement shade tree, contact your local Nebraska Extension office.