Reminders and Notices

Do You Have Ash Trees on Your Property?

Do You Have Ash Trees on Your Property? Be Sure to Have Them Checked for Borers.

Decorah, IA (January 11, 2022) – The Emerald Ash Borer (EAB) is now firmly established in Decorah and infesting trees throughout the community. This introduced pest kills all species of ash trees by tunneling under the bark, destroying tissue that is essential to the life of the tree. Symptoms include cracked bark, branch dieback, new shoots sprouting from the trunk of the tree, and patches of light brown bark where woodpeckers have chipped off the gray outer bark while searching for the insects (called flecking).

Flecking is easily identified this time of year because woodpeckers are busy foraging for the larvae. In early stages of the EAB infestation, flecking will appear in the upper canopy of the tree (on smaller branches). As the infestation progresses, signs of flecking will continue throughout the lower canopy and down the trunk of the tree. In most cases, the tree should be removed as soon as possible when flecking is noticed on the trunk.

Trees that are heavily infested by EAB must be removed. The wood of trees killed by the borers dries out quickly, becoming brittle and hazardous, so it is wise to monitor trees regularly for presence of the pest and remove them while it is still safe to do so.

If a homeowner has an ash tree or suspects they may have an ash tree on their property, the City is highly recommending that it be checked by an arborist. If not badly infested, trees can be treated by having a certified applicator inject a suitable insecticide into the trunk of the tree. Treatments vary and must be reapplied throughout the life of the tree. Treatments applied to the soil are not recommended as they can be less effective, harmful to pollinators, and more likely to be overapplied. Please check with a local arborist for a treatment option that best fits the needs of you and your tree.

Diversity in our urban tree canopy is vital, so a disease or pest infestation is less likely to affect such a large portion of trees all at once. When planting, take a look at tree species in your neighborhood and choose one that is less common. One of the most commonly planted trees is maple. Homeowners are strongly cautioned against planting maple trees on private property due to overpopulation. All but one species of the maple genus are prohibited in boulevards until a healthy diversity in the urban canopy is achieved.

For more information, please contact City Forester Sam Hogenson at 563-277-5153 or by e-mail at cityforester@decorahia.org. Additional information is also available on the Decorah Tree Board website at https://www.decorahia.org/tree-board.

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