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Emerald ash borer advances through Midwest

Emerald ash borers, invasive insects that have destroyed tens of millions of ash trees in Michigan and Wisconsin, are seen emerging from an infested ash tree. For more information on EAB in Michigan, go to https://www.michigan.gov/mdard/0,4610,7-125-2390_18298---,00.html. (U.S. Department of Agriculture photo)

WAUSAUKEE, Wis. –The emerald ash borer is a small, bright green metallic wood-boring beetle that is not native to North America.

It is responsible for killing millions of ash trees in the upper Midwest, including many in Marinette County.

EAB currently is only known to be found in the town of Wagner, the town of Goodman and the city of Niagara within Marinette County and not found within Oconto or Florence counties at all. As it continues to spread throughout our area, it truly places all ash trees in its path in imminent danger and that includes many thousands of acres with ash trees just in our area.

The current status of EAB presence in Wisconsin is tracked by the Department of Agriculture, Trade, and Consumer Protection and updated on a map at https://datcp.wi.gov/Documents/EABDetectionsWisconsin.pdf.

The two primary infestations in Marinette County are in Wagner and Niagara and are described as “spotty, but heavy.”

It is highly likely EAB is established in other areas along the Menominee River between those locations, and landowners everywhere in the area should be on the lookout for the telltale signs/symptoms which ash trees exhibit when infested with EAB.

What are those signs? Well, dying ash trees is one obvious answer, but there are other reasons why ash trees may perish, including water stress, root problems, diseases, etc. So, we need to look for a couple telltale signs.

Woodpeckers find EAB infested trees quickly and flake, or “fleck,” the bark off in their pursuit of the larvae which are feeding between the bark and wood. The inner bark or wood will show as a pale, nearly cream color, in stark contrast to the grey outer bark of ash trees.

Initial infestations often start higher on the tree trunk, but fully infested trees will have flecking to ground level. The larval feeding activity is how the insect kills trees. Their larvae feed on the cambium layer in serpentine trails, very effectively girdling the tree.

The other telltale sign develops after the main trunk is in the process of dying or is already dead. The root system of the tree is still fairly healthy and in an effort to survive, it sends up new shoots from the base of the tree. This phenomenon is known as epicormic branching and makes the tree look like a shrub, as it may send up dozens of these new shoots.

Why is EAB a big deal?

EAB attacks and kills ash trees, including white, green and black ash, all of which are present in large numbers in forests and backyards in our region. Ash trees being killed by EAB can quickly become brittle and hazardous and can be a challenge to remove if you wait until the tree is dead. In urban areas, or for yard trees, removing an infested ash tree before it becomes a hazard will be safer and less costly than waiting until the tree is dead or nearly dead.

You can protect individual trees. If you are nearby one of the current infestation zones and have ash trees in your yard that you want to protect, it can be done.

There are various insecticide treatments that can be utilized to protect individual trees. Some of these treatments are available as homeowner formulations, others need to be applied by certified tree care professionals. Either way, most of them need to be applied each year to afford true protection.

The current treatment options are listed and described at: https://eab.russell.wisc.edu/considerations-for-homeowners/.

Of course, you have the option of planning for the removal of your landscape ash trees and replacing them with other species, if you aren’t comfortable either with the cost of treatment or the use of annual insecticide applications. If there are no known EAB infestations near you, utilizing a whole-tree treatment is not warranted or recommended.

Forest situations are a different story. The only effective treatments are individually applied and are cost-prohibitive for forest management. As such, forest landowners near infected zones may want to contact a forester to understand their options.

Waiting until EAB is present will dramatically limit options. Current silvicultural guidelines for ash forests are available in the “What You Can Do” tab on the Wisconsin Department of Natural Resources’ EAB website, at https://dnr.wi.gov/topic/ForestHealth/EmeraldAshBorer.html.

Whether from a front yard or a forest, ash wood that is infested with EAB must be managed properly. Most importantly, it should not be moved.

EAB adults have been found to be able to emerge from ash wood that has been cut and split for up to two years. Thus, when dealing with EAB infested trees, cut and split any wood that you want to use as firewood and stack it in the immediate area for two growing seasons or use it as firewood on site.

Other information sources

In addition to the websites already noted above, there are other general sites from which you can easily access EAB information. One of these is the main DATCP EAB page, which has links to all the other sites. It is https://datcpservices.wisconsin.gov/eab/index.jsp.

If you are concerned that you may have EAB in your ash trees, you can contact Linda Williams, northeast Wisconsin forest health specialist, at 920-360-0665 or Linda.Williams@wisconsin.gov.

It is important that you have the correct diagnosis of EAB before reacting with management strategies.

Scott Reuss can be reached by leaving a voice mail at 715-732-7510 or by e-mail at scott.reuss@wisc.edu.

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