Bedbugs are infesting U.S. households on a scale unseen in more than a half a century, and homeowners and apartment dwellers are taking desperate measures to eradicate the bloodsuckers, with some relying on dangerous outdoor pesticides and fly-by-night exterminators. The problem has gotten so bad that the Environmental Protection Agency warned this month against the indoor use of chemicals meant for the outside. The agency also warned of an increase in pest-control companies and others making "unrealistic promises of effectiveness or low cost." Ohio authorities, struggling against widespread infestations in Cincinnati, Columbus, Dayton and other cities, are pleading with the...