The past couple of years the maple tress have been a little more prolific due to good growing conditions in previous years. In the lawn, they will die from repeated mowing, so no need to use herbicide unless it's needed for some other broadleaf weeds you might have in the lawn. Be sure that if you do use a chemical control that you select one that says "safe for lawn". Any broadleaf weed-killer with control them, but it's not necessary to apply unless you have other weeds to control. Like I said, repeated mowing events will take care of the problem just fine :)