The potential presence of codling moth, Cydia pomonella L., in apples shipped to countries within the 30th latitudes has raised concerns that this pest could establish and spread in these countries. Previous research demonstrated that codling moth in apples handled under simulated commercial cold storage conditions and held under short day lengths could not break diapause and emerge in sufficient numbers to establish a minimum viable population. This study expands the in-fruit work by examining the ability of codling moth to establish a laboratory population under a short photoperiod of 12:12 (L:D) h, as compared with a long photoperiod of 16:8 (L:D) h. Codling moth larvae were collected from field infested fruits in 2010 and 2011. Moths were collected from the infested fruits and separated into two groups representing the two daylength conditions. In total, 1,004 larvae were monitored for adult emergence and ability to generate a subsequent population. Larvae held under the photoperiod of 12:12 (L:D) h generated only one moth in the 2 yr period, whereas larvae held under the photoperiod of 16:8 (L:D) h generated 186 females and 179 males, that sustained subsequent generations on artificial diet under laboratory conditions. These results indicate that under controlled environmental conditions, codling moth cannot complete diapause and emerge in sufficient numbers to sustain a viable population when held under a short photoperiod.