Fate of codling moth (Lepidoptera: Tortricidae) in harvested apples held under short photoperiod

Codling moth, Cydia pomonella L., is a cosmopolitan pest of pome and stone fruits. It has been identified as a quarantine pest of concern in a number of countries where it is not known to occur, most of them tropical or subtropical countries. Although considerable work has been done on the basic biology and physiology of this temperate pest, little is known on its potential to develop and establish in tropical environments with short photoperiods and few to no days below 10 degrees C. Apples were harvested over three field seasons (2007-2009) from unmanaged orchards in central Washington State and subjected to simulated commercial cold storage at 1.1 +/- 2 degrees C for up to 119 d. After cold storage, infested fruits were held at 20 degrees C under a 12:12 L:D photoperiod for up to 6 mo. Over the entire experiment only 27% of the larvae collected exited the fruit and cocooned. Of those 27%, only 1.06% of larvae held under a 12:12 L:D photoperiod successfully emerged as moths. No moths emerged when host fruit would be available in a representative importing country in the tropics over the 3 yr of testing. These results indicate that codling moth in apples from the Pacific Northwest pose little threat of surviving and establishing in tropical regions where daylength is insufficient to break diapause and the chilling requirement is not met.