Laboratory and field studies supporting augmentation biological control of oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), using Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae).

Abstract

BACKGROUND\nOriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a cosmopolitan pests of fruit trees in temperate regions. Control of G. molesta is challenging because larvae feed in concealed locations and have evolved resistance to many pesticides. We compared three commercially available species of Trichogramma for efficacy against G. molesta in the laboratory assays and tested releases of the promising species in a pear orchard.\n\n\nRESULTS\nLaboratory assays indicated that T. dendrolimi parasitized G. molesta at the highest rate. Parasitoids took longer to oviposit in older host eggs, and fewer eggs were parasitized when they were more than three days old. Field tests produced ca. 60% cumulative parasitism of sentinel G. molesta eggs with one release of T. dendrolimi, with most parasitism occurring within 24 h. Female wasps dispersed up to 12 m from release points with a bias toward upwind movement.\n\n\nCONCLUSION\nWe calculated that, for each generation of G. molesta, 900,000 wasps per hectare, in three releases three days apart, each distributed among release points 10 m apart, would reduce fruit damage by half in an orchard where 50% of fruit would otherwise be damaged. Although augmentation of T. dendrolimi is a viable tactic for reducing G. molesta populations and fruit damage, it will require integration with other compatible control tactics in order to provide commercially acceptable levels of control in orchards experiencing significant pest pressure.