A New Bedford man was charged Wednesday morning in the Oct. 14 slaying of Joyce Howland, a retired elementary school teacher from Fairhaven, prosecutors said. Joshua Silva, 36, was charged with murder and armed robbery in New Bedford District Court, the Bristol district attorney’s office said. An initial investigation suggested that Howland and Silva knew each other, the Globe reported previously. Howland was killed in her Fairhaven home. Silva was scheduled to be arraigned Wednesday afternoon in New Bedford District Court.