A Bug in Your Ash

Ash trees (Fraxinus spp) are found throughout Ohio and are a co-dominant species in a number of habitat types, from Silver Maple/Ash/Elm swamp forests that are vital to amphibian conservation, to Sugar Maple/White Ash/American Basswood upland forests which provide significant habitats for numerous bird and mammal species.  That means the ash is one of the most common or important species in an ecological community.

As you walk the trails at TWC, you’ve probably noticed rather a lot of trees on the ground. Like so many other places, our ash trees here at TWC are being destroyed by the Emerald Ash Borer (EAB), the destruction caused by the EAB seriously weakens the trees. So, sadly, to ensure public safety, we had to take the decision to cut down all the ash trees along the trails, any trees that don’t pose a threat are left standing, and will continue to provide habitat for years to come.

What is the EAB and why is it such a problem?

Photo courtesy of Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

A stunning emerald green jewel beetle measuring just 1/2 inch-long and 1/8-inch-wide, the EAB goes by the Latin name Agrilus planipennis.  Native to eastern Asia from eastern Russia through northern China, Japan, and Korea. Those beautiful adult beetles do snack on ash leaves, but they don’t do much damage and wouldn’t be much of a problem on their own. The larvae (the immature grub like stage) are another matter, they are greedy feeders, chewing away on the inner bark of ash trees creating a matrix of multiple channels.  Trees use the inner bark to transport water and nutrients, the channels created by the EAB larvae drastically disrupt that ability.

We do have native ash borer species here in North America, but because they’ve evolved alongside them our native ash trees have developed resistance to them, so while they still damage the trees there is a natural balance. EAB’s are new and have spread really fast, so our native trees have little or no resistance to them, and the damage they do seriously weakens the trees. Three of our native borers love to attack stressed or dying trees, so once weakened by the EAB trees are far more susceptible to attack by those species too – a double whammy for the poor stressed ashes!

How did it get here, and how has it spread?

Like many other invasive (non-native) species, the EAB was probably an accidental introduction, finding its way to North America in imported wood packaging or crating material. It’s likely that the EAB might have been around for up to 12 years before it was first discovered in Michigan in 2002, by that time many ash trees in the southeast of the state were dead or dying.

From a small number of beetles in the beginning, with few natural enemies the EAB population soon expanded and started to spread. On February 28, 2003, it was confirmed in Ohio, and as of March 1 2017 these interlopers have been found in 29 states and two Canadian Provinces.

The adult beetle is able to fly at least 1/2 mile from the tree where it emerges, so there was some natural movement, but the rapid spread of the EAB suggests that many were unintentionally relocated along with infested ash shipping pallets, nursery trees, logs, or firewood. The movement of ash nursery trees and ash logs with bark have now been regulated, and a quarantine zone set up.  Transporting firewood outside of the quarantined areas is illegal, but many people remain unaware of the regulations or of the seriousness of the problem, and the movement of infested firewood remains a big issue.

There’s a wide range of research underway to find a solution to the problem including early detection programs and chemical control measures, but at present the best we can do is try to contain the outbreak, so remember

  • Don’t move firewood. EAB larvae can survive hidden in the bark of firewood. Remember: buy local, burn local.
  • Inspect your trees. If you see any sign or symptom of an EAB infestation, contact your State agriculture agency.
  • Talk to friends, neighbors and co-workers about EAB and what they should be aware of on their trees.
  • Ask questions. If you receive ash nursery stock or firewood, know its point of origin and your supplier, as larvae could be hiding under the bark.


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