Emerald Ash Borer - What to do?

By Jim Walsh, ISA Board Certified Master Arborist, Vineland Tree Care

Since Emerald Ash Borer (EAB) was first discovered near Detroit in 2002, it has "killed tens of millions of ash trees in southeastern Michigan alone, with tens of millions more lost in Ohio, Illinois, Indiana, Pennsylvania, West Virginia, Missouri, Wisconsin, Virginia, Ontario and Quebec", according to www.emeraldashborer.info. That's at least forty million dead ash trees in seven years.

In 2008, EAB was found in eastern Wisconsin. In early 2009, a pocket of EAB-infested trees were discovered south of La Crosse. In spring of 2009, EAB was found in the Midway area of St Paul. In February of 2010, more infested trees were found in Prospect Park in Minneapolis. Based on the ash tree losses east of Minnesota, the oncoming threat of widespread loss of our native and landscape ash trees looks real. But there is still time to act.

Planning

Start by making an assessment of the overall condition of all your trees, not just the ash. Tree owners are often in love with deeply flawed trees that should have been removed long ago. Determine how all the trees on the site interact together. For example, an ash tree might be falling apart, or suppressing the growth of a more valuable tree. What are the goals for the landscape? While many people are averse to removing trees for any reason, a significant number of tree owners are equally disinterested in using chemical treatments. And then there is the budget for doing the work. Might it be cheaper to remove in the winter? Could we wait to treat until fall? Should I treat all my ash trees to save them? Or cut them all down because they are going to die anyway?

Planting

Planting another tree or trees depending on the specifics of your site and the goals for your landscape might be the best plan. Although there is always time for planting, get going before you lose the time it takes to grow more shade. Plant a variety of tree species to minimize the threat of any one insect or disease threat. Planting only one variety is not the correct response to the EAB problem.

Chemical Controls

There are different chemicals available to treat EAB. Basal-drench, soil-injected or trunk-injected chemical treatments, not spraying, are the best application methods. By the time the obvious signs of infestation appear it is too late for chemical treatment. If chemical treatments make sense for your valuable ash tree(s), you should start before infestation. When properly applied, applications prior to infestation can be effective. Annual or biannual reapplication is required depending on material used.

Regardless of how many ash trees are treated, many more plantings of new trees will be needed. A recent news story set in Detroit featured outside interviews with very few trees in the background. Most of the shade trees we sit under were planted by those who came before us. If we want to keep our cities green, we need to get planting.

Jim Walsh can be reached at 612-872-0205 or jim@vinelandtree.com