Wednesday, 12 August 2020

Kiss Your Ash Trees Goodby

Image or ash trees whose crowns are partially and fully defoliated by Emerald Ash Borer.

Nobody wants the crown layer of their woodland to look like this.

Wisconsin’s woodlands are changing. Emerald Ash Borer (EAB) is causing the greatest die-off of trees in the state since Dutch elm disease arrived in the 1960s. If you have ash trees on your property, you must learn to recognize EAB damage and quickly take action. In Wisconsin, that means black, green or white ash. Time is not your friend; indecision will remove any options. The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has a website that shows where EAB is prevalent.

First, cruise your timber. Early detection is your best and only defense. Check out the Wisconsin DNR for website for woodlot owners. Treatment must be made to individual trees and completed before 1/3 if the crown is lost.


One of the best ways to identify emerald ash borer damage is through the “D” shaped holes emerging insects leave in the bark. Unfortunately, these holes are approximately 3/16 inch in diameter and may first appear rather high in the tree. The cream colored larvae living under the bark can be 1½ inches long. These are exit holes for the larvae that are emerging to morph into adults.

Most landowners will first spot the infestation by observing leaf loss in the crown. This crown thinning can easily be overlooked or written off as storm damage. By the time the damage is obvious, it is probably too late.

Image of green ash tree with significant bark blonding

Outer layers of bark begin to fall off an ash as EAB larvae eat their way through the sapwood.

Bark blonding takes place when the bark of an infested tree shards to shed the outer layer of its bark. The tree is essentially dead at this point. Blonding occurs because the sapwood below the bark is dead and outer layers of bark are drying out and stuffing off. 

Image of debarked ash trunk with EAB tunnels

Peal away the bark of an infested ash tree and you will find tunnels in the sapwood created by the EAB lava.

The EAB lays it eggs under the bark. When the eggs hatch, they spend two years developing in the cambium layer of the ash tree. They eat the sapwood, burrowing tunnels are they feed. The tunnels interrupt nutrient flow. Eventually, limbs and even the trunk die as tunnels completely cut the supply of sugars and water.

What’s Next?

If tree you want to save is less than 47″ around at chest height, you may be able to treat it yourself. You can apply a liquid soil drench homeowner product for about $20-35/year. An arborist should treat larger trees or those with special circumstances. Their treatments involve directly injecting trees under the bark. Those treatments typically cost several hundred dollars and must be repeated every 2-3 years.

The cost or removing dead ash trees start at $1,000 and more, depending on size and location. Your only choice, if you have too many trees to treat, may be to conduct a timber harvest.

More Informaiton

The Emerald Ash Borer Information Network has the latest information about he pest and how to control it.



April 2019

Monday, 15 April 2019

How long would it take one tree to make a forest?

That depends on several factors. First and most important is the species of tree. Some species of trees must receive pollen from a different tree because pollen from the same tree will not create viable seed. If you plant only one tree of that type, it will never result in another tree, much less an entire forest.

Species, like silver maple, are fast growers and reach maturity earlier than other species. Fast maturing trees might begin producing viable seed as soon as three or four years. Other species might take as long as ten years before they produce viable seed.

Some trees produce a large quantity of seed, while others produce relative few seeds. Add to this, the seed from some trees has a high germination rate, while other species produce large quantities of seed but much of it will never germinate.

Now start looking at environmental factors. These can dramatically influence who quickly tree regeneration takes place. Among these environmental factors are:


Will the seeds get enough rain and sunlight at the right time so they germinate and survive long enough to become viable seedlings? Will really hard winters kill the seed before it ever gets a chance to sprout? Will floods wash away the seed?

Even if the seed germinates and seedlings survive, weather will impact growth rate. Different species have differing requirements for temperature and rainfall. Inclement weather, such as drought and late spring warming, can reduce annual growth by half or more.


Lots of animals and micro organisms see tree seeds as food. Mice, bear, raccoons, squirrels, weevils and fungi devour tree seeds. Depending on how heavy the predation nearly the entire seed crop for a year might be consumed by predators.


Wildland fire kills trees. It cooks the sapwood of many species which destroys the ability of the tree to move water and nutrients, even if the bark does not burn. Young trees that do not yet have thick bark are almost certainly burn over.

Some fire tolerant trees, including many species of oaks, are fire tolerant. Older trees have bark thicker enough to insulate it from fire. Young trees may be burnt to the ground (0r nearly so) but the tree has the ability to re-sprout new growth from the root crown and begin again.

Shade Tolerance

Some trees are early succession species, which means they thrive after disturbance like a fire or disease when other trees around them have died and there is lots of sunlight available. These species would be the ones that could regenerate a forest more quickly.

Other species, called late succession, thrive when grown under shade. Among these are many maple species. Some late succession species can also grow with an abundance of sunlight, but others succumb to drought too easily without damp soil to cool and keep their young roots moist.

I suspect you were looking for a definite answer to your question. Unfortunately, like most questions involving biology, the answer is, “it depends.”

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