Assessment of symbiont‑targeted control on non‑target stink bugs and their associated egg parasitoids: Could this technique be suitable against Halyomorpha halys in New Zealand?

The potential arrival of Halyomorpha halys in New Zealand jeopardizes a vast range of crops. Therefore, different preparedness strategies are being assessed before its arrival. A symbiont-targeted control strategy might be used along with other control tactics such as biological control. Prior its implementation, it is necessary to assess its potential impact on non-target stink bug species and their associated egg parasitoids. In this study, the effect of symbiont-targeted control was evaluated on three stink bug species in New Zealand, Oechalia schellenbergii (a native predatory species), Nezara viridula (a cosmopolitan pest) and Monteithiella humeralis (a non-pest adventive species). The interference of anti-symbiont treatment of egg masses with their associated Trissolcus egg parasitoids, namely T. basalis and T. oenone, was also tested. A variable response to symbiont elimination was observed in stink bug species, with N. viridula and M. humeralis undergoing high mortality and no negative effect detected for O. schellenbergii. Parasitism of N. viridula by T. basalis declined on egg masses treated with an anti-symbiont biocomplex or water. Similar results were obtained for T. oenone parasitizing eggs of M. humeralis; while, a parasitism increase was observed for O. schellenbergii egg masses exposed to anti-symbiont treatment and treated with water. These results confirm previous evidence of species-specific response to anti-symbiont control and indicate a moderate and variable effect on egg parasitism. Such responses suggest that symbiont-targeted control would not significantly interfere with the native insect communities that may interact with H. halys, encouraging the future incorporation of symbiont-targeted control in pest management programs.