Physiological Host Range of the Tachinid Istocheta aldrichi , a Potential Biological Control Agent for the Japanese Beetle in Europe

ABSTRACT

Classical biological control, which is the introduction of natural enemies from an invasive pest's area of origin, has been proposed repeatedly to control the invasive Japanese beetle Popillia japonica Newman (Coleoptera: Scarabaeidae) in invaded areas. In the absence of area‐wide management strategies to control P. japonica in Europe the release of the fly Istocheta aldrichi (Mesnil) (Diptera: Tachinidae) is considered. However, although I. aldrichi has been released in the USA, in Canada, and the Portuguese Azores, no laboratory tests have been done to determine which non‐target host species are suitable for the development of the parasitoid (physiological host range). Thus, as first step of a risk–benefit analysis to assess the potential for the introduction of I. aldrichi to Europe, we investigated the physiological host range of the parasitoid by conducting laboratory‐based no‐choice tests with 14 European non‐target beetle species from three subfamilies of the family Scarabaeidae. As is the case for most parasitoids, we predicted that host acceptance for oviposition and suitability for development of I. aldrichi will decrease with decreasing phylogenetic relatedness to P. japonica . The assessment was done using a sequential exposure scheme, in which P. japonica was exposed before and after the non‐target beetle to ensure oviposition readiness of the parasitoid. Testing revealed that six out of 14 non‐target beetle species were accepted for oviposition by I. aldrichi females. As predicted, this included all three tested beetles within the subfamily Rutelinae, but also one Cetoniinae, and one Melolonthinae. However, successful development of the parasitoid was only found in two Rutelinae: Mimela junii (Duftschmid) and Anomala vitis Fabricius. Based on the information from this study, choice tests and further investigations into the ecological host range of I. aldrichi should be conducted to further analyse the risks of using the fly as a classical biological control agent in Europe.