There should be no ‘saw vs. save’ ash-tree debate anymore

A recent MinnPost article and letter show that the “saw vs. save” debate continues over how best to manage the emerald ash borer (EAB) infestation that threatens the billion ash trees in our state (“In Longfellow, a divide over how to deal with a common tree killer: emerald ash borer,” Feb. 4, and “Longfellow ash crisis is about more than pesticides vs. no pesticides,” Feb. 6).

There is no debate about the need to replace infested and low-quality ash trees. However, the saw side of the debate often includes the notion that replacing all ash trees, even healthy mature trees, is cost effective. In the Feb. 4 article, a Minneapolis official is quoted as saying, “it’s actually cheaper to just remove the ash trees and begin replacing them immediately.” Wrong! Two healthy, average-sized ash trees can be protected for more than 20 years for the cost of removing and replacing just one tree.

Trees are the only urban infrastructure that increases in value over their useful lives. A replacement sapling in Minneapolis will take 30 years before it can provide the same $165 in annual economic and environmental benefits lost by removing the healthy mature ash tree it “replaced.”

Minneapolis is relying on the strategy used by cities first hit by the infestation many years ago. Unfortunately, that strategy is a failure. It wastes public resources to remove and replace healthy trees, destroys public investments in green infrastructure, and it shifts the burden to property owners as the beetles find and attack private trees. For many years now, scientists have agreed that the most effective strategy is to reduce the number of beetles, not their ubiquitous food supply. 

The MinnPost article said, “Minneapolis’ approach also avoided a potentially nasty public fight over using pesticides.” Another mistake. The city’s policy relies on the fallacy that replacing a healthy ash tree avoids the use of neonicotinoids and protects pollinators. In fact, the preferred pesticide to inoculate against EAB is emamectin benzoate, which is not a neonicotinoid. Also, most replacement trees the city is planting will likely have been treated with pesticides, including neonicotinoids, at the nursery to prevent the spread of additional plant insects and diseases. Ironically, the Minneapolis strategy could be using more neonicotinoids than a science-based protocol to manage EAB. 

While Minneapolis raises regressive property taxes to pay for its obsolete strategy, other cities should listen to the scientists: Marla Spivak, the Distinguished McKnight Professor in Entomology at the University of Minnesota, and an internationally recognized expert on bees, has said that the benefits of trunk-injected emamectin benzoate for ash trees outweigh the minimal potential harm to bees.[1] Three years ago, Deborah McCullough, a professor of entomology and forestry at Michigan State University, stated, “There is no reason for a landscape ash tree to die from emerald ash borer anymore.”[2]

In sum, there should be no “saw vs. save” debate anymore. Compared to the removal-only approach, a science-based management of the infestation that protects the high-quality public ash trees and replaces the rest can cut public costs in half and preserve four times the tree canopy. And that means preserving four times the tree benefits that were the reason the trees were planted in the first place.

When this infestation hits your city, listen to the scientists, save your best trees and public funds, and enjoy the benefits our mature trees provide.  

Michael Orange, Principal, ORANGE Environmental, LLC