Seasonal pattern of infestation by the carob moth Ectomyelois ceratoniae in pomegranate cultivars

Pomegranate (Punica granatum L.) orchards in the Middle East are typically composed of a mix of different cultivars in which variation in fruit infestation by carob moth Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) has been observed. However, seasonal variation in infestation and adaptation of the carob moth to this cropping system have not been explored. We monitored the progress of fruit infestation in 10 pomegranate cultivars during the growing season of two consecutive years in pomegranate orchards of Iran. Overall, levels of infestation in fruits were strongly correlated with susceptibility to fruit cracking in pomegranate, so that cracked fruits and cracking-susceptible cultivars were infested the most. However, this pattern changed during the season. Infestation was first observed on cracking-susceptible cultivars. At this point almost all cracked fruits were infested. Towards the end of the season, infestation in uncracked fruits and cracking-resistant cultivars increased. Uncracked fruits seem better overwintering sites for carob moth as under simulated winter conditions, survival of insect larvae in uncracked fruits was >3 times higher than in cracked fruits. Taken together, our data reveal that cracked fruits of pomegranate are the better host during the growing season, while uncracked fruits better sustain carob moth population in winter. It seems therefore advisable not to grow cracking-susceptible and cracking-resistant cultivars together in the same area.