Anticipating the arrival of a new stinkbug pest in continental Europe: what can we learn from preemptive host specificity tests for biocontrol?

The egg parasitoid Gryon aetherium Talamas (Hymenoptera: Scelionidae) is a promising candidate for biocontrol of Bagrada hilaris Burmeister (Hemiptera: Pentatomidae) in the Southwestern USA. Bagrada hilaris is a worldwide invasive pest of crops in the family Brassicaceae. The present study aims to evaluate the parasitoid’s host range in a European context. These tests complement studies underway in California and provide risk information for a potential release of G. aetherium in southern continental Europe where B. hilaris is likely to spread in the future. Of the 11 non-target species tested, four pentatomids were in the physiological host range of G. aetherium: Carpocoris mediterraneus, Dolycoris baccarum, Graphosoma italicum and Ancyrosoma leucogrammes. Parasitism rates on these four species were lower in choice than in no-choice conditions. Surprisingly, the three Eurydema spp. that belong to the same tribe as B. hilaris (Strachiini) and feed on plants in the family Brassicaceae were not parasitized. No parasitism was observed on the cosmopolitan invasive pentatomids Nezara viridula and Halyomorpha halys, nor on the rhopalid Liorhyssus hyalinus. Parasitoids that developed from non-target species were larger than ones developing on B. hilaris and took more time to complete development.