Willow Grove-based Asplundh Tree Expert Co. is huge, privately owned corporation with more than 36,000 employees and estimated annual sales of $3.5 billion, according to Forbes, which counts it as one of America’s largest private companies. But now, Asplundh finds itself the recipient of some very unwelcome attention thanks to charges just filed in federal court. An Asplundh vice president, Larry Gauger, 45, of Wayne, has been charged with visa fraud and conspiracy relating to his work at the company. Two other Asplundh managers have been charged as well, according to the Department of Justice, but their names have yet...