Carposina sasakii Matsumura (Lepidoptera: Carposinidae) is a serious pest of apples and peaches in Korea and Japan. Because of its limited distribution, C. sasakii has been identified as a quarantine pest in several countries. The Controlled Atmosphere/Temperature Treatment System (CATTS) was tested as an alternative to methyl bromide fumigation to control C. sasakii in apples. The fifth instar was the most tolerant immature stage to a heat treatment of 44°C for 20 min. When the apples infested with different stages of C. sasakii were treated under CATTS conditions (heating rate of 16°C/h, chamber temperature of 46°C, final core temperature of 44°C under 1% O₂/15% CO₂ atmosphere), young larvae (first-fourth instars) did not survive after 40 min exposure, but the fifth instars required an exposure of at least 60 min to attain 100% mortality. A partial heat shock protein 90 (hsp90) was cloned and showed inducible expression in response to heat shock at 44°C. CATTS suppressed transcription of the hsp90 gene. Apples did not show any appreciable loss of quality in relation to fruit firmness, sweetness, and decay after a 60 min CATTS treatment. These results suggest that CATTS can be applicable to control C. sasakii in apples.