Physiological host range of Trissolcus japonicus in relation to Halyomorpha halys and other pentatomids from California

Brown marmorated stinkbug (BMSB), Halyomorpha halys Stål (Hemiptera: Pentatomidae), is native to Asia and an invasive urban and agricultural pest in the US. In California (CA), BMSB has been recorded attacking specialty crops such as almonds and peaches. The egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), a key BMSB natural enemy native to Asia, is a candidate for classical biological control efforts targeting BMSB in CA and other parts of the US Trissolcus japonicus cannot be introduced deliberately into CA for BMSB control without US federal regulatory agency approval which is contingent on better understanding of its host range and specificity. Consequently, the host specificity and physiological host range of T. japonicus was evaluated under laboratory quarantine conditions by exposing eggs of BMSB and non-target pentatomid hosts (native and other exotic species) found in CA to T. japonicus. No-choice and binary-choice experiments provided female T. japonicus with equal unrestricted access to eggs of BMSB and non-target pentatomids. In addition to BMSB, eggs from six of ten resident pentatomid species found in CA were parasitized by T. japonicus. However, T. japonicus attack and emergence rates were consistently higher on BMSB when compared to non-target species. These results suggest that T. japonicus is oligophagous, but BMSB is a superior reproductive host compared to non-target pentatomid species that were evaluated. The implications of these findings for classical biological control efforts targeting BMSB in CA are discussed.