Physiological host range of Istocheta aldrichi: a biological control agent of Popillia japonica
Popillia japonica (Coleoptera: Scarabaeidae - EPPO A2 List) originates from Japan and is established in North America and was recently introduced in a small part of the EPPO region. The larvae feed on roots of a wide range of plants whereas adults feed on foliage of various host plants. The biological control agent Istocheta aldrichi (Diptera: Tachinidae) has been utilised as a classical biological control in the USA and Canada. Native to Japan, I. aldrichi has shown varying levels of parasitism of P. japonica (90 % in Japan and up to 70 % in the USA). I. aldrichi was released in the Azores (Portugal) in 1993 although it is likely it failed to establish as it was not detected afterwards. Throughout its native range in Japan and its introduced range in North America, I. aldrichi has only been recorded parasitising P. japonica. The physiological host range is the range of species (hosts) on which a biological control agent is able to survive, reproduce and complete its life cycle under optimal conditions (e.g., confined conditions). For I. aldrichi, this was assessed by conducting laboratory-based no-choice tests with 14 European non-target beetle species from three subfamilies of the family Scarabaeidae. The assessment was done using a sequential exposure scheme, in which P. japonica was exposed to the biological control agent before and after the non-target beetle to ensure oviposition readiness of the parasitoid. The results showed that five out of 14 non-target beetle species were accepted for oviposition by I. aldrichi females. This included all three beetle species which were tested and belong to the same subfamily (Rutelinae) as P. japonica. It also included one species from each of the subfamiles Cetoniinae and Melolonthinae. Successful development of the parasitoid was only found in two species from the Rutelinae: Mimela junii and Anomala vitis. Further investigations into the ecological host range of I. aldrichi should be conducted to assess the risks of using the fly as a classical biological control agent against P. japonica in Europe.
Sources
Valenti R, Makovetski V, Kenis M, Haye T, Seehausen ML (2026) Physiological host range of the Tachinid Istocheta aldrichi, a potential biological control agent for the Japanese beetle in Europe. Experimental and Applied Entomology (early view) https://doi.org/10.1111/eea.70172