Tritrophic effects mediate host suitability for two parasitoids of the carob moth (Lepidoptera: Pyralidae), infesting pistachio kernels

Abstract

The carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae), is an important pest of pistachio causing direct damage to nuts during ripening, and in storage. We examined the tritrophic effects of 5 pistachio cultivars, representing the full range of kernel suitability for E. ceratoniae, on 2 larval parasitoids, Habrobracon hebetor (Say) (Hymenoptera: Braconidae), a gregarious, synovigenic, idiobiont, ectoparasitoid, and Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae), a solitary, pro-ovigenic, koinobiont, endoparasitoid. The suitability of pistachio cultivars for development and reproduction of the 2 parasitoids was closely correlated, despite their divergent lifestyles and developmental patterns, and paralleled variation in kernel suitability for host larvae. Although kernels of the most resistant cultivar reduced demographic parameters of the parasitoids, the potential impact on numerical responses was minor. Successful biological control of carob moth within the vulnerable period of nut ripening will likely depend on the functional responses of earlier generations of adult parasitoids emerging from other fruit and nut crops, or those released in an augmentation program.