Thanks for your question.  I will try to assist you.  I need just a little more  information for me to start thinking about your situation.   

You indicated that about four years ago, you had an encounter with Japanese beetles.  Was that a singular experience or since then have you had further evidence of their presence?  Have you ever had treatments for grubs in your yard?  Have you ever noticed patches of your yard dying or becoming brown?  Any evidence of your lawn being torn up by animals searching for grubs?

I don't believe that your experience with Emerald Ash Borers has anything to do with your lawn being bumpy.

Looking forward to hearing back from you.  Thanks for consulting with us.



Thanks for getting back to us.  I am currently doing a bit of research on your situation and should have my answer back to you by tomorrow.  Thanks much for your patience and thank you for consulting us.

Thanks again for your question and especially for your patience in our trying to assemble an appropriate answer to your question.

Here are our thoughts:

1). The presence of Emerald Ash Borers probably has no relationship with your yard being bumpy. The taking down of the ash trees and the increasing degree of bumpiness in your yard, we think, is purely coincidental.

2). Over time, foot traffic, heavy machinery, or even frequent mowing can compact the soil, causing uneven surfaces. Have any of these events recently occurred?

3). You had mentioned that about four years ago you had an issue with Japanese Beetles. The underground grubs associated with these beetles can lead to uneven (i.e., “bumpy”) turf. Various animals such as raccoons and crows will disturb a yard in their attempts to eat these grubs. Perhaps these soil disturbances are only now becoming evident?

4). Thatch is a layer of organic matter that can accumulate between the soil and grass. Excessive thatch can make a yard uneven. If you have not done so recently, consider dethatching your yard in late summer to early fall 2024.

Insofar as trying to improve your turf, here are our further thoughts:

1). For those areas that are bumpy, spread a thin layer (1/4 to 1/2 inch) of high quality (i.e. containing NO weed seeds) topsoil over them. Rake it evenly and water to allow the added soil to settle. Smooth things off. Reseed if existing turf is sparse. This could be done now (late May 2024) but don’t delay much longer. Otherwise this should be a late summer (early September 2024) project.

2). Aerate the lawn to relieve soil compaction. This involves creating small holes in the soil to allow air, water, and nutrients to penetrate. This could be done now (late May 2024) or in early September 2024. After the aeration process, numerous grass plugs will be left on the surface of the turf. Distribute these around and attempt to fill in the depressions in the lawn.

3). Although it might be tempting, avoid using a roller to smooth things out. Generally this only compacts the soil, which would only compound your current problems.

See the following for information on these and related points:

https://www.rainbowlawncare.com/common-lawn-issues/ - :~:text=Topdressing, or adding a small,occurring in the first place.

https://parkwaylawn.com/news/smooth-bumpy-lawn/

https://extension.umn.edu/yard-and-garden-news/ask-extension-dead-bumpy-lawn

https://yardandgarden.extension.iastate.edu/how-to/bumpy-rough-lawns

Good luck with your efforts. Please get back to us if you have further questions.