The parasitic complex of Halyomorpha halys: preliminary data on adaptation of native egg parasitoids to the invasive host

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera, Pentatomidae) is a polyphagous sap sucking pest native to Asia that, after spreading in the US and Europe, invaded Italy causing a relevant phytosanitary emergency. In Sicily, H. halys was recorded for the first time in 2017 but no crop damage has been associated to the species up to now. Its control mainly relies on the use of insecticides with toxicological and environmental consequences. To minimize these side effects, the exploitation of biological control as an eco-sustainable alternative sounds promising. In this study, we assessed in laboratory bioassays the potential adaptation of an indigenous egg parasitoid belonging to Telenomus genus (Hymenoptera, Scelionidae) on the new invasive pest. The host suitability, parasitism rate and mortality caused by the parasitoid on H. halys were also evaluated at different exposure time intervals (from 1 to 7 days). The parasitoid impaired the development of H. halys embryos. The stink bug hatching rate decreased from 93.42 to 73.62% along the 7 days of exposure to the parasitoids. Conversely, the incidence of apparently parasitized eggs increased respectively from 1.25 to 14.32%. Although we recorded a low successful parasitism rate, the total parasitism on H. halys was significantly higher after 7 days of parasitization than at shorter exposure times. This aspect is analysed and the potential impact of the indigenous parasitoid on the exotic pest is thus discussed.