Hello Joanne,

Diagnosis of damage such as this is difficult from photos alone. We need more information before giving an informed opinion…

What has been the lawn maintenance routine? Mowing height? Irrigation? What fertilizers and pesticides/herbicides were applied and when? Were any insecticides applied? Was pre-emergent or post-emergent crabgrass herbicide applied? When did this problem first manifest? Last spring or fall or this spring? Does the client ever smell skunks in the area or see raccoons?

Does the client see any evidence of insects? This article has instructions on how to check for grubs: https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

Here is an article on sod webworms and their damage: https://www.canr.msu.edu/resources/sod_webworm_tips_for_your_lawn

But rather than having the client check for each possible insect, she should probably submit a 12 x 12 inch sod sample (straddling the border between the dead area and still green area) to the MSU Diagnostic lab. Their exam may be able to tell which insect to treat for.

After taking the grass sample, send it to the MSU Diagnostic Labs for positive identification. The following website describes the services and the fee structure for analysis performed by the Diagnostic Lab.: https://www.canr.msu.edu/pestid/

This website provides directions and tips for taking a good sample: https://www.canr.msu.edu/pestid/submit-samples/