A laboratory experiment demonstrated that in San Jose scale, Quadraspidiotus perniciosus (Comstock), the male is susceptible to a number of insecticides. Diazinon was the most effective as it killed the males before they emerged from their shells. Males emerged and survived for a short time before being killed by residues of azinphosmethyl and endosulfan. In an orchard, a petal fall spray of diazinon or Penncap E applied when male scales started to emerge gave good control of San Jose scale and was as effective as three summer sprays of diazinon timed to emergence of crawlers. Penncap E was ineffective against the crawlers. Post-bloom sprays are necessary to control infestations of incrusted scale because a pre-bloom oil application usually fails to contact live scale that may be underneath one or more layers of old dead scale.