Combining physiological host range, behavior and host characteristics for predictive risk analysis of Trissolcus japonicus

Abstract

Halyomorpha halys is an Asian pentatomid that has recently invaded several countries worldwide, where it has become a severe pest. Classical biological control focused on the scelionid egg parasitoid Trissolcus japonicus appears to be the most promising long-term solution. However, non-target risks need to be included in cost/benefit analyses. Physiological host range tests were conducted by offering T. japonicus females a single hemipteran egg for short (2 h) and long (24 h) exposure periods, and recording the behavior and parasitization acceptance/success during the short exposures. Of the 16 different hemipteran species tested in no-choice experiments, 9 species were accepted and suitable for T. japonicus development. Among pentatomids, Palomena prasina and Rhaphigaster nebulosa were accepted at rates comparable to H. halys, while species accepted at lower rates included Acrosternum heegeri, Carpocoris mediterraneus, C. purpeiripennis, Dolycoris baccarum, Piezodorus lituratus and Peribalus strictus. The other 7 hemipterans tested, including two coreids and one reduviid, were never parasitized. The use of a short-term exposure of 2 h revealed no differences with the 24-h exposure that has been widely used in physiological host range testing. Thus, T. japonicus oligophagy observed in other studies was confirmed by using our extremely simplified laboratory protocol. Moreover, the host egg morphology was correlated with the acceptance rates, permitting us to propose a new predictive approach for non-target studies. However, further research with more complex experimental designs that account for environmental conditions is needed to confirm laboratory predictions of host specificity under actual field conditions.