The hyperparasitoid Marietta picta (Hymenoptera: Aphelinidae) mediates competitive interactions between two parasitoids of Paratrioza sinica (Hemiptera: Psyllidae): Tamarixia lyciumi (Hymenoptera: Eulophidae) and Psyllaephagus arenarius (Hymenoptera: Encyrtidae)

Abstract Both the ectoparasitoid Tamarixia lyciumi Yang (Hymenoptera: Eulophidae) and the endoparasitoid Psyllaephagus arenarius (Hymenoptera: Encyrtidae) are solitary nymphal parasitoids of Paratrioza sinica (Hemiptera: Psyllidae), a pest of goji berry, Lycium barbarum . Moreover, T. lyciumi is frequently attacked by a hyperparasitoid Marietta picta Andre (Hymenoptera: Aphelinidae) in the field. To analyze competitive interactions between T. lyciumi and P. arenarius mediated by M. picta , we evaluated interspecific host discrimination and larval competition between T. lyciumi and P. arenarius , and the effect of M. picta on their competitive interactions, under laboratory conditions. The results showed that T. lyciumi could discriminate hosts pre-parasitized by P. arenarius , but not vice versa. However, P. arenarius was a superior intrinsic competitor in multiparasitized hosts regardless the order of parasitism. Although multiparasitized hosts produced more P. arenarius and fewer T. lyciumi after exposure to M. picta , the total number of emerging T. lyciumi and P. arenarius did not decline significantly, and sex ratios did not change. Thus, larval superiority would appear to favor the establishment of newly introduced P. arenarius in the Ningxia region, while the inferior competitor T. lyciumi is able to utilize interspecific host discrimination to avoid larval competition. Competitive interactions between T. lyciumi and P. arenarius are mediated by M. picta , and the observed host–parasitoid–hyperparasitoid interactions potentially facilitate their collective coexistence in biological control of P. sinica .