I once scared the bejesus out of a man with a chain saw in his hand. It was May 1, and he was a utility company arborist, working his way down my street, cutting off limbs from trees that overhung the road.
He was just doing his job when a mad woman in pajamas, with a baby on her hip, ran out of a house and screamed: “Get away from that tree! Do you call yourself an arborist? Haven’t you ever heard of Oak Wilt?” He backed away.
Oaks must been pruned before March 15th to prevent picnic beetles from visiting open wounds later in the Spring and infecting the trees with Oak Wilt. Here is the tree I rescued:
More about Oak Wilt in Wisconsin. Do not let your local utility or your landscape contractor prune oaks after March 15.