By Kathleen Cue, Nebraska Extension Horticulture Educator
Last week’s finding of the emerald ash borer (EAB) west of Fremont has ash tree owners wondering what to do next. There are several options but first it’s helpful to know if your ash tree lies within a 15 mile radius. What is the importance of knowing if your ash lies within this radius, you ask? Treatments stress trees, which is justifiable if EAB is imminent, but not so much if EAB is far away.
From Fremont, the 15 mile radius likely includes the communities of Arlington, Scribner, North Bend and Wahoo. Regardless if your ash tree is urban or rural, ash tree owners within the 15 mile radius will want to take note.
First, doing nothing is an option. Some ash tree owners simply want to enjoy their tree while it is still alive and plan to have it taken down once the tree has died. One caveat to this plan is that the costs of tree removal will go up considerably once EAB becomes widespread. Further, ash becomes dangerously brittle fairly quickly after it has died. Arborists do not climb dead or dying ash trees, which also drives removal costs upward.
Second, ash tree owners who choose treatment need to be aware that not all ash trees are equally good candidates for treatment. Things like trunk splits, planted too deep, raised beds around trees, no central leader and untended branch breakages all contribute to tree stress and diminished tree health. This translates into uneven insecticide distribution internally, leaving vulnerable areas open to EAB infestation. If the ash tree is suffering from one of these conditions, spending the money to treat and getting EAB anyway is probable.
For healthy trees that tree owners would like to keep, treatments would take place in spring and are based on the diameter of the tree at 4 ½ feet from the ground. If the diameter at this height is less than 20 inches, then a drench containing imidacloprid or dintefuran may be applied to the soil. Trees 20 inches or more in diameter at 4 ½ feet from the ground will need a certified arborist for ememectin benzoate insecticide injections. Keep in mind that one treatment does not impart a lifetime of protection for the tree. Repeat applications will need to be made, with the timing based on the treatment method, for the life of the tree.
The circumstances of the ash tree owners themselves should be a consideration when deciding whether to treat or remove trees. Sinking time and money, year after year, into an ash tree is going to impact young tree owners much more strongly than others, especially when considering the same amount of time could be invested in a replacement tree. The Emerald Ash Borer Decision Guide is an excellent resource for helping ash tree owners determine what course of action makes the most sense for them.
Photo: Emerald Ash Borer on a penny