Thank you for your inquiry.
Do you know if you have the invasive narrow-leaf cattails as well as native cattails?
Here is some helpful information from the Midwest Invasive Species Information Network that gives you more information particularly about the narrowleaf version as well as control:
Keep in mind that permits are usually required for herbicide use in water bodies and wetlands. For information see MDEQs Aquatic Nuisance Control website at: www.michigan.gov/deqinlandlakes.