Customer called today wanted to know if it was ok to put some expandible spray foam in a tree cavity. She is worried about bees or something making a nest in the hole. I know usually we are told to leave cavity alone but was wondering if anyone ever heard of this. Customer wanted to use foam from home depot thought it sounded almost like perfect solution but wondered about harm to tree? Have not seen tree or size of hole. Customer says its a little bigger than the size of grapefruit. Any ideas????