Emerald ash borer likely expanding diet

OHIO—As if the forests of Manitoulin haven’t had enough bad news when it was determined a couple of years ago that the emerald ash borer had moved into the neighbourhood, a recent release from the researchers at Wright State University in Ohio reports the bad news that the invasive and highly destructive species that has wreaked destruction upon woodlots across southwestern Ontario has expanded its diet beyond its namesake ash trees.

The emerald ash borer was discovered in North America in 2002, accidentally imported from Asia through the likely medium of untreated packing crate wood, and the invasive pest has already caused billions of dollars in damage over the intervening decade. In fact, the Canadian Forest Service has pegged the costs to Canadian municipalities of replacing the trees, popular for their ornamental effect and comforting canopy, at more than $2 billion.

In a paper published this week in the Journal of Economic Entomology, researchers at Wright State University in Ohio reported that the emerald ash borer was now attacking whitefringe trees, the closest relative of the ash tree and an increasingly popular ornamental tree in both the US and Canada.

“Things aren’t looking good for ashes in North America and now other species,” said Don Cipollini, a plant physiology professor at Wright State University who first detected the signs of the insect expanding its diet.

Dr. Cipollini said other trees and shrubs closely related to the whitefringe now need to be watched for ash borer infestations. Those species include lilacs, forsythia and privet, and in bad news for martini fan, cultivated olives, which are grown in the southeastern US, are also a close relative of the whitefringe and thus could also be threatened.

On a somewhat brighter note, Dr. Cipollini said that there is no sign of risk for trees that are not related to the ash, such as maples, and previous tests on walnut and hickory trees, which are more closely related to the ash, indicated those trees do not support the emerald ash borer.

Dr. Cipollini first discovered the infested whitefringe trees last August while travelling along a bike path in Yellow Springs, Ohio. He discovered that five out of the 20 trees he investigated were damaged, and upon expanding his study group, he found infestations of whitefringe trees in other parts of Ohio.

The question now facing researchers, and of course arborists and gardeners, is are the ash borers expanding their diets or did they have a wider palate to begin with?

Dr. Cipollini suggest that latter is likely the case.

The borer was first detected in Canada in the Windsor area in 2002 and its rapid spread highlights the importance of not importing firewood or other untreated lumber into an area.