Field Cage Assessment of the Neotropical-Native Parasitoid Ganaspis pelleranoi as a Biocontrol Agent of the Invasive Pest Ceratitis capitata

Ceratitis capitata (Diptera: Tephritidae), or medfly, is an invasive pest widespread in Argentina, where standardized management methods, such as cultural and chemical controls, are commonly implemented. The success in controlling medfly populations depends on implementing preventive, sustainable, long-term, and eco-friendly eradication/control strategies across all invaded environments. One strategy may involve augmentative biological control using parasitoids adapted to local conditions, such as Ganaspis pelleranoi (Brèthes) (Hymenoptera: Figitidae), a Neotropical-native parasitoid that mostly forages on tephritid larvae in a broad range of fallen fruit. Two hypotheses were tested in the current study: (1) G. pelleranoi females are more efficient in controlling medfly larvae infesting different fruits as the density of released females progressively increases, and (2) such parasitoid-induced host mortality capacity remains when host density is increased. Parasitism (reproductive effects) and additional host mortality (non-reproductive effects) were the indicator variables of parasitoid-induced host ability. Trials were performed in field cages (semi-field conditions) using two medfly-multiplier host fruit species, namely sour orange and peach, and with variations in both parasitoid release and host larval densities. Three major findings were highlighted: (1) G. pelleranoi females successfully parasitized host larvae on peach and sour orange, regardless of their strongly differing physical features, although medfly larvae in peaches were significantly more susceptible to the parasitoid; (2) medfly mortality significantly increased in both peach and sour orange relative to the gradual increase in released G. pelleranoi females, regardless of the increase in host density offered to parasitoids; and (3) G. pelleranoi females induced a substantially high host die-off rate when the additional mortality was added to the analysis, which was not revealed when parasitism alone was regarded as a medfly mortality variable. Such outcomes may provide relevant information for implementing an augmentative biological control against medfly using indigenous parasitoid species within an eco-friendly fruit fly pest management approach.