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  • Jennifer Karras

Corey Wierema Puts Down Roots as City Forester

By Jennifer Karras Corey Wierema was named the city forester of Lake Forest in 2016 after an eight-year stint as assistant city forester. He and his staff are in charge of the thousands of trees on public land in the city and make sure they are trimmed, watered and, when necessary, removed. Has Lake Forest experienced any recent concerns regarding our trees? Is the emerald ash borer still an issue?

For the last four to five years, we have been dealing with a lot of precipitation in the spring months. When we have wet springs, the trees can be susceptible to a lot of fungal activity throughout the growing season. That fungal activity combined with other environmental stressors have really caused some unbalance in our urban forest.

"It’s a community that values these open spaces and understands the importance of maintaining them for the future," says City Forester Corey Wierema. A recent concern has been bur oak blight (BOB). Bur oak blight is a late-season fungus that affects bur oak trees and can cause severe decline if the tree is hit with it for multiple years in a row. With regards to emerald ash borer, we are still dealing with that insect but at a far lower infestation level. As long as the food source (ash trees) are around, we will always be battling this pest to some degree.

What will the impact of cicadas be on trees?

Lately, there has been a lot of talk about the 17-year cicadas as broods emerge across the U.S., but we have a couple of more years to go (May 2024) before we have to deal with them in Lake Forest. While they are not a major threat, cicadas can damage young, newly planted trees by laying eggs on smaller branches. If too many branches on a young tree are damaged, the whole tree could die. Covering young trees with a net prior to the cicada hatch might be necessary if the infestation level is high. The use of insecticide to try to control the insect is NOT recommended.

What trees do you recommend homeowners plant?

I always try to promote native trees, because they are important to the lifecycle of our native insects, birds, and other species, but ultimately I think diversity is most important. It fortifies the community against widespread tree loss in the event of an infestation like the emerald ash borer and Dutch Elm Disease.

What sets Lake Forest apart from other communities?

Without a doubt, community support and community engagement set Lake Forest apart. It’s not very common to have both support and engagement at the level that you find here. I find myself at times taking for granted the beautiful open space. Then it sinks in, you realize how fortunate you are to work in such a great community. It’s a community that values these open spaces and understands the importance of maintaining them for the future. Our parks, golf course, natural areas, lakefront facilities, and trees are all true assets to the community. In addition to all of that, our partnership with Lake Forest Open Lands continues to play a critical role in helping the community promote and maintain our great natural areas.

What do you love most about your work?

I love that the decisions I make in my job today will have a lasting impact on the health and beauty of Lake Forest for years to come. I can drive through Lake Forest and see trees I planted 20 years ago. Or I can show you 100-year-old trees that the Forestry Section maintains so that, hopefully, they will last another 100 years. I also meet so many residents who love and appreciate the natural history of this community and want to do what they can to preserve it for future generations. It’s very rewarding when I can help our residents identify and address a problem with their own trees or provide the guidance they might need to improve or maintain the trees on their properties and easements. I also couldn’t ask for a better crew. Tree care can be hard and dangerous work. Our crew shows up every day (and often at night when storms have knocked down a large tree or limb) to make sure our urban forest remains safe and healthy. If you’re a Lake Forest resident and have a question for Corey, please e-mail him at or call him at (847) 810-3564.


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