Impact of ant predation and heat on carob moth (Lepidoptera: Pyralidae) mortality in California date gardens

Dates, Phoenix dactylifera L., undergo a natural fruit abscission during the summer in California date gardens. Many of the abscised dates become lodged in the date bunch, and we demonstrated that carob moth, Ectomyelois ceratoniae (Zeller), prefer to use these dates as a reproduction host compared with dates that fall to the ground. We also found that abscised fruit shaken onto the ground had significantly fewer live carob moth larvae than fruit that remained in bunches in the tree. Mortality in the dropped fruit was attributed to predation by two native ant species, the fire ant Solenopsis aurea Wheeler, and the California harvester ant, Pogonomyrmex californicus (Buckley), in concert with extreme summer ground temperatures. Dates that fell in the full sunlight rapidly increased in temperature, which resulted in larvae either exiting the fruit (exposing them to ants) or dying in the fruit. Removal of abscised dates from bunches may provide a possible management strategy for carob moths in California date gardens.