What is the best way to manage Emerald Ash Borer from an economic perspective? Dr. Richard J. Hauer, Ph.D of the University of Wisconsin-Stevens Point was awarded a 2011 John Z Duling grant to study this question. His findings point to retaining the ash tree population:
Emerald ash borer (Agrilus planipennis) kills ash trees native to North America. Regardless of management options taken, EAB will cost communities and property owners money. Doing nothing is one option with letting ash mortality progress unabated. Costs associated with this include reduced property values, tree removal, and tree replanting. Another option promoted is the preemptive removal of ash before they are infested. This approach suggests ash will die anyway so removing trees prior to EAB infestation helps spread the cost over time. Replacing the removed trees is also a potential part of this option. Preemptive removal still costs money with tree removal, reduced property values, and replanting. A third option involves treating ash with insecticides to delay tree mortality that would occur from EAB infestation. Chemicals including Emamectin Benzoate (Tree-äge™) and Imidacloprid (Merit®, XytectTM, IMA-jet, and Imicide®) show promise and high levels of success with 90% and higher reductions in EAB larvae reported.
This research developed economic models to compare these options using an approach that models net tree value as a function of tree value – management costs. This approach has been effectively used to develop economic management approaches for other urban forest health issues and now with decision making with ash populations and EAB. In brief, net tree value was derived for actual and hypothetical ash tree populations from tree value (CTLA and i-tree approaches) – management costs based on tree size and approach taken (i.e., removal, replacement, treatment). Modeled ash populations can represent a variety of age class scenarios. Surviving ash trees (i.e., treated or those yet infested have simulated annual growth (i.e., 0.4 inches, 1.02 cm per year) and annual mortality (~2% per year, size dependent). The planning approach allows economic values to be discounted to the present value.
Research outcomes show that retention of ash tree populations was a preferred outcome to doing nothing and letting ash die from EAB. Less desirable was removing ash preemptively as the value of ash tree populations lost from removed trees was greater than management costs to retain ash trees.