Effect of center cut strand thinning on fruit abscission and Ectomyelois ceratoniae (Lepidoptera: Pyralidae) infestation in California date gardens.

The carob moth, Ectomyelois ceratoniae (Zeller), infests different date, Phoenix dactylifera L., fruit stages during the summer months in southern California. Abscised fruit in the kimri stage become heavily infested when they get stuck in tight date bunches and do not fall to the ground. Previous work on date palm horticulture found that the percentage of fruit abscission could be reduced by thinning fruit out of the bunch. Our objective in this study was to determine whether center cut strand thinning reduced fruit abscission and, if so, to determine any concurrent effect on carob moth summer population densities. We found that the center cut treatment did not alter fruit abscission at any of the four date gardens used in the study. However, thinning in May reduced July carob moth densities at the four date gardens by 54-97%. The percentage reduction was apparent into September, ranging from 30 to 81%. This reduction was significant in two of the four fields, and we believe that center cut thinning in these fields altered the bunch architecture, allowing abscised fruit to fall to the ground. Implications for field management of the carob moth are discussed.