Wednesday, June 10, 2015

A Not So Precious Emerald

Emeralds are beautiful translucent green gems that are valued throughout the world. Here in northcentral Pennsylvania our forests have emeralds – but not the precious gem kind. These emeralds are emerald ash borers, an insect, one of the metallic woodborers. 

The emerald ash borer is less than an inch long and is, indeed, emerald green. It was apparently introduced from northeast Asia, where it is native, by way of ash lumber used in packing materials. Fist detected in Michigan in 2002, it has since spread to many other states killing an estimated 50 million ash trees in the process.

Emerald ash borer became noticeable in the Big Woods about six years ago when ash trees began showing the diagnostic light patches of bark – which means the beetle had arrived several years earlier.

The light patches are created as woodpeckers flake off the bark’s outer ridges in their search for beetle larvae.



The woodpecker’s flaking of the bark does the tree no harm; it’s the beetle larvae’s feeding galleries girdling the tree which result in the tree’s death. The larvae feed on the cambium layer and the inner bark (called phloem); once the maze of galleries is dense enough the tree dies.

From the time the emerald ash borers first begin feeding on a tree until it dies seems to take about three years; from the time it arrives in an area until virtually all the ash are dead is often less than ten years.

Beetles emerge from beneath the bark through “D”-shaped holes during late May and June.

The beetles then mate and the females lay their eggs on the bark of ash trees, typically in July. The newly hatched larvae bore through the bark, feeding and growing throughout the fall. With the advent of cold weather the larvae create chambers in the wood below their feeding galleries and overwinter there. In the spring the insects pupate, changing to their adult form.

All this may be old news to people in Michigan, Indiana and Ontario where the emerald ash borer has been killing ash trees for over a decade, but here the ash has only been dying for a few years and the folks in northern New York and New England have yet to see its effects.

Forest landowners in this area are preemptively cutting their ash trees before they die since ash logs deteriorate rapidly and lose their economic value. The ash on our property succumbed to the emerald ash borer last year – the wood now graces our firewood pile. A tree that three years ago looked perfectly healthy by last summer had but a few scattered leaves, given the maze of galleries beneath the bark, it would not have survived another year. 

Unless biological controls which can successfully control emerald ash borer are found it looks like we can say good-bye to ash baseball bats, snowshoe frames, hockey sticks, tool handles and flooring. Yes, I know that maple is increasingly being used for bats now, and most new snowshoe frames are aluminum, and modern hockey sticks aren’t made of ash, and many tool handles are fiberglass and oak is more popular for flooring. But ash is flexible and strong and shock absorbing and traditional – and as an old fuddy-duddy I prefer ash to aluminum and fiberglass.


  1. The bugs are just arriving here, and Ash are the single most common early successional trees in the valley, including lots of them on our own property!

  2. An informative article with excellent photos. It has been here in Fulton County for awhile and am noticing that most of the ash trees in my area are dead.

  3. Great post on the Emerald Ash borer, I hope they can be controlled. Awesome shots of the woodpeckers. Thank you so much for linking up and sharing your post. Have a happy weekend!

  4. wow what a cool insect, I've never seen one like that :-)


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