Varying levels of acceptance and egg abortion of the invasive Halyomorpha halys by different strains of native parasitoids.

The brown marmorated stink bug Halyomorpha halys (Hemiptera: Pentatomidae) is an invasive pest of global concern affecting many agricultural crops. In the invaded areas (North America, Europe), the impact of native biological control agents is generally low and mostly attributable to generalist species. Native egg parasitoids, for example, often attack H. halys eggs but their offspring are unable to develop. The lack of co-evolved relationships between H. halys and native egg parasitoids could be reduced over time if native egg parasitoids adapt to the new host, either by avoiding them (reducing behavioural acceptance) or by gaining the capacity to successfully exploit them (increasing developmental success). The likelihood of adaptation and consequences for biological control is expected to depend on the amount of within-and among population and species variation in acceptance, host killing ability (egg abortion), and developmental success. The aim of this study was to investigate the level of acceptance, abortion rate and development success of five strains of each of the native North American egg parasitoids Trissolcus euschisti and Telenomus podisi. One-week old mated parasitoid females were exposed to an H. halys eggs clutch at 25 °C. Oviposition behaviour was recorded for 5 hours for each female. Parasitoid emergence was recorded and after the emergence of the nymphs, the unhatched eggs were dissected and classified as aborted, empty, containing nymphs or parasitoids. As expected, all parasitoid strains showed a high (but varying) level of acceptance of H. halys eggs, but offspring development was extremely rare. Varying rates of H. halys egg abortion due to unsuccessful parasitism were also observed, with more abortion in the egg masses exposed to T. podisi compared to those exposed to T. euschisti. This study will be useful to understand at which level the genetic variance may influence the different adaptation level of egg parasitoids to the new host allowing the development and implementation of further efficacy biocontrol strategies.