By Steve Katovich, US Forest Service, St Paul, with contributions from Mike Reichenbach, University of Minnesota Extension

Ash mortality from EAB, Ann Arbor MI. Steve Katovich photo from forestryimages.org. Click for original.

In 2002, a small emerald green beetle native to Asia was found killing ash trees in the Detroit area.  The beetle was given the common name “emerald ash borer” or EAB for short. It had apparently arrived on infested pallet wood or crating material, perhaps as far back as the early 1990’s.  The infestation spread undetected for 10 years.  Surveys in 2002 quickly confirmed a massive infestation with almost every ash tree in the Detroit metro area affected.

An ash tree in Ely brightens the local landscape in September. Steve Katovich photo.

Since then, EAB populations have been found in 10 states and 2 Canadian provinces.  Of greatest concern is the transport of infested firewood from Illinois, north of Milwaukee, and in the Upper Peninsula of Michigan.  By transporting firewood, visitors from these areas could very easily initiate EAB outbreaks here in Minnesota.  Beetles could also arrive on an infested nursery trees or perhaps in logs arriving at a mill.

EAB is a tremendous tree killer, and Minnesota woods include a huge ash component in both rural and urban forests.  In fact, EAB is proving to be such an efficient killer that it seems likely that few ash trees will populate our landscape in the future.

PA DCNR photo from forestryimages.org. Click for original.

At this time, the best strategy is to delay EAB’s arrival as long as possible. Given enough time, researchers may yet uncover some key tools that will even out the battle between the insect and ash trees.  Homeowners can help.  Firewood should be obtained and burned locally.  It is not a good practice to transport firewood long distances.  Even within Minnesota it would be prudent to avoid transporting firewood from the Twin Cities to a cabin or campground. The Michigan experience has shown a number of state wide campgrounds were infested with EAB, as a result of firewood transport.

Despite our best efforts, EAB will eventually arrive in Minnesota.  It would be best if any new introductions were found early.  Everyone is encouraged to report unusual ash tree mortality.  Extensive woodpecker activity on ash trees can be a sign that EAB larvae are active under the bark.  This is most easily observed in the late winter when bark flakes cover the snow and the stripped bark stands out against a white background.

Photo by Howard Russell from forestryimages.org. Click for original.

Minnesota landowners with ash do not need to panic. It will likely be years before EAB begins to impact Minnesota forests.  But, it might be wise to rethink long term management plans for stands that have an extensive ash component. Rather than waiting for EAB to arrive, some early stand intervention could reduce the risk of extensive tree mortality. The insect attacks both healthy and weak trees, there’s little that can be done to create resilient stands.  Landowners can take advantage of management actions planned in their woodland to harvest trees before the insect reaches Minnesota.  After the insect is in MN quarantines may make it difficult to transport harvested logs.

Think you may have EAB?

Forest Pest First Detector volunteers have been trained in EAB identification, signs and symptoms, look-a-like insects, and even other species of concern including gypsy moth, Asian long horned beetle, Sirex woodwasp, and thousand cankers on walnut.

If you think you have found emerald ash borer, go through the steps at Do I have emerald ash borer? (246 K PDF) to be sure. You can also call Forest Resources Extension at 612-624-3020.

You can also email Arrest.The.Pest@state.mn.us.

Tags: ash decline, ash mortality, EAB, emerald ash borer, forest, Forest health, insect, invasive species, katovich, Minnesota, MRR, reichenbach