Replacement of Megastigmus pistaciae Walker (Hymenoptera: Megastigmidae) by Eurytoma plotnikovi Nikol’skaya (Hymenoptera: Eurytomidae) in pistachio orchards in southern Italy

Investigating the effect of non-native herbivore species in the new areas is vital for understanding their effects on native crops and the interactions that the newly arrived species have with any natural native herbivores and predatory species. The pistachio-seed wasp Eurytoma plotnikovi Nikol’skaya (Hymenoptera: Eurytomidae) is an invasive species on pistachio groves in Sicily, southern Italy; thus, the current study investigated its effects on pistachio crops and the native pistachio-seed wasp Megastigmus pistaciae Walker (Hymenoptera: Megastigmidae). The results showed that fruits in Pistacia vera pistachio groves were infested only with E. plotnikovi, which had been able to replace M. pistaciae after only a decade. Female E. plotnikovi emerge between May and June, but the males are rarely seen. No natural enemies were detected for E. plotnikovi in the study sites, highlighting an important phytosanitary issue for pistachio nut production in Sicily.