Spring is upon us and with the warming weather will certainly come door hangers and mailings offering the latest and greatest options for healthy lawns and happy trees and shrubs. I have never seen a “happy” tree or shrub that I was aware of, but if there are “unhappy” trees in our area, they are most certainly our ash trees. Common along street sides, community parks and home landscapes, this particular tree species (Fraxinus) was a common replacement for the many American elms that succumbed to Dutch elm disease 30-40 years ago. So here we are in 2017, with yet another invasive wiping out a monoculture we created ourselves due to a lack of imagination and diversity.
A Little Bit of EAB History
Hopefully by now most have of you have heard about emerald ash borer (EAB), an invasive insect originally from China, identified in 2002, which has wreaked havoc on ash trees across 27 states. This insect is amazingly effective at killing ash trees. Once it is detected, 80 percent of all ash trees within a community are dead or dying within 8 years. The remaining 20 percent will soon follow; to save ash trees the only option is the use of targeted insecticides for the remaining life of the tree.
To Treat or Not To Treat
This brings us back to the “home place.” If you are a homeowner in the greater Omaha metro area, from eastern Omaha to Greenwood, where EAB has been confirmed, what should you do and what things should you consider? If you’re in western Nebraska, it’s worth it to begin thinking about it as well, though the spread may take many years. I’ll warn you that this article just skims the surface of EAB management options. For more detailed information, go to http://nfs.unl.edu/nebraska-eab.
To treat or not to treat is one of the most common questions. Much of the answer depends on the condition and placement of ash tree/s in your landscape. If it’s in the back of the lot with no direct benefit, such as shade that reduces home cooling costs, it may be a candidate for removal and replacement, especially if there is top dieback or other structural or health issues. However, if the tree is located in a prominent location in front of your landscape or providing significant shade or other benefits, treatment may be an option.
Only healthy, structurally viable ash trees should be considered for treatment and only when EAB is known to be within 15 miles of your location. Why wait until the insect is known to be within 15 miles? The 15 mile recommendation provides a balance between protecting valuable landscape trees and limiting the negative effects of unnecessary treatments. Treating trees outside of this zone provides little or no benefits to the tree, may be a waste of money, exposes humans and the environment to unnecessary pesticides and trunk injections may cause unnecessary damage to the tree. On the other hand, it’s an excellent time to plant a new replacement tree and avoid the eventual cost and expense of treatment and/or disposal.
Trunk injections are one of the best treatment options as the chemicals are directly injected into the tree. When applied by a professional, they can be very effective but must be done every 1-2 years for the life of the tree. Mid-May to early June is generally the optimal treatment window for most injections, with an average cost of $100 per year for a 20-inch diameter tree, depending on the treatment. These treatments can be effective but all options have consequences beyond the cost—including injury to the tree and potential harm to people, pets, wildlife and the broader environment. (See Selecting Trees for EAB Treatments and EAB Guidelines for Homeowners)
The best long-term solution for ash trees is to replace them with a diversity of native and regionally-adapted species. Planting a new tree to the east, south or west of the existing tree should afford enough direct sunlight to get a young tree established. The sooner another tree is established, the less eventual loss will be felt. Truly the time to plant a tree is now.
Making a decision to remove, replace and reprioritize your landscape with increased diversity puts you well ahead of the game. There are plenty of excellent replacement species: Kentucky coffee tree, bur oak, shumard oak, hackberry, hybrid elms and catalpa, a personal favorite. Select and choose a large maturing tree, something beyond the flash of spring flowers or fall color, that will produce a canopy worthy of the years and generations ahead.