The seasonal prevalence of the occurrence of the San Jose scale crawler, Diaspidiotus perniciosus, in an apple orchard in Morioka city, Iwate prefecture was investigated from 2004 to 2006. First-generation crawlers emerged from late June to mid July, when the accumulated temperatures ranged from 300 to 600 degree days above 10.5 °C from March 1. Second-generation crawlers emerged from late August to mid September, when the accumulated temperatures ranged from 1000 to 1500 degree days. The occurrence of first- and second-generation crawlers peaked when the accumulated temperatures ranged from 380 to 450 and from 1100 to 1200 degree days, respectively.