Monday, 28 September 2020

Identify Tree Pests

image of people learning to identify tree pests

Landowners learn to identify tree pests. [photo credit: UDFS Northeastern Area State and Private Forestry,]

There are plenty of brochures to help landowners identify tree pests. I have a file folder full of publications pests like emerald ash borer. If you are like me, I see something that does not look quite right and want to know what’s going on. It may be nothing, but then maybe it is a real problem — time to figure out which.

Bring in the Experts

Fortunately, for those of us who live in Wisconsin, the UW Madison has experts whose job it is to diagnose tree problems for Wisconsin residents. The Plant Disease Diagnostics Clinic has an experienced plant pathologist who specializes in plant disease diagnostics. Additionally, the Wisconsin Insect Diagnostic Lab handles plant pests like insects, bugs, aphids, caterpillars. Questions or images can be sent to the Wisconsin bug guy, PJ Liesch:

Many of us prefer the do-it-yourself approach when dealing with tree pests. We want to know what we are seeing in the field without sending off samples and waiting for results. If you are like me, knowing for myself is better than having to depend on somebody else. I contact these folks for touch calls; they are great. I just do not want to load them down when I can figure the problem out for myself.

Do It Yourself

The Inventory Pest Evaluation and Detection (IPED) method provides an effective way to diagnose tree pest or disease problems. You can use this clear, simple and accurate way to detect and monitor pests wherever you live. The IPED Field Guide will help you identify the signs and symptoms of tree stress, insect pests, and diseases, letting you to make informed decisions. This guide is not intended to be used for diagnostic work, but rather as a resource guide to help you use the i-Tree Streets application at: is external).


August 2020

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.