Classical Biological Control of Japanese Beetle

• Forschungsstelle: BLW
• Projektnummer: 21.04

Schlüsselwörter (Deutsch)

Japanischer Käfer; Popillia japonica; Biologische Schädlingsbekämpfung; lstocheta aldrichi; Schädling

Schlüsselwörter (Englisch)

Japanese beetle; Popillia japonica; biological control; lstocheta aldrichi; pest

Schlüsselwörter (Französisch)

scarabée japonaise; Popillia japonica; lutte biologique; lstocheta aldrichi; ravageur

Schlüsselwörter (Italienisch)

Coleottero giapponese; Popillia japonica; controllo biologico; lstocheta aldrichi; parassita

Kurzbeschreibung (Englisch)

The Japanese beetle, Popillia japonica, native to East Asia, was accidentally introduced into Switzerland (Ticino) in 2017. It is a destructive generalist pest with adults and grubs feeding on important agricultural crops. Climate models suggest that P. japonica is able to establish north of the Alps. Classical biological control could provide an area wide, long-term solution, preventing crop losses and reducing insecticide use. The most promising biological control agent is the tachinid fly Istocheta aldrichi, native to Japan. The general objective of the project is to assess the potential of I. aldrichi as classical biological control agent against P. japonica in Switzerland, focusing on its host specificity, the climatic suitability of Switzerland for establishment. In parallel, the potential presence of native parasitoids of P. japonica in the Ticino will be studied. Fly puparia will be imported from Canada to establish a laboratory rearing in CABI’s quarantine facility. Adults of non-target species present in Switzerland will be collected in the Ticino for exposure to females of I. aldrichi in no-choice tests, determining its potential host range. Pheromone traps will be placed at various locations in the Ticino to assess the phenology of P. japonica. In parallel, the phenology of the fly and beetle will be monitored in Canada. These data will be used to model the synchronisation of the occurrence of P. japonica and I. aldrichi in different climatic zones of Switzerland.

Kurzbeschreibung (Französisch)

Le scarabée japonais, Popillia japonica, originaire d'Asie de I'Est, a été accidentellement introduit en Suisse (Tessin) en 2017. C'est un ravageur généraliste destructeur dont les adultes et les larves se nourrissent d'importantes cultures agricoles. Les modèles climatiques suggèrent que P. japonica est capable de s'établir au nord des Alpes. La lutte biologique classique pourrait apporter une solution à long terme à I'échelle d'une région, en prévenant les pertes de récoltes et en réduisant I'utilisation d'insecticides. L'agent de lutte biologique Ie plus prometteur est la mouche tachinide lstocheta aldrichi, originaire du Japon. L'objectif général du projet est d'ëvaluer le potentiel de I. aldrichi comme agent de lutte biologique classique contre P. japonica en Suisse, en se concentrant sur l’ëtude de la spécificité pour son hôte et sa capacité à s'établir en Suisse. En parallèle, la présence potentielle de parasitoïdes indigènes de P. japonica au Tessin sera étudiée. Des pupes de mouches seront importées du Canada pour établir un élevage en laboratoire dans l'installation de quarantaine de CABI. Des adultes d'espèces non ciblées présentes en Suisse seront collectés au Tessin pour être exposés à des femelles d' I. aldrichi dans le cadre de tests de non-choix, afin de déterminer sa gamme d'hôtes potentielle. Des pièges à phéromones seront placés en divers endroits du Tessin afin d'évaluer la phénologie de P. japonica. En parallèle, la phénologie de la mouche et du coléoptêre sera étudiée au Canada. Ces données seront utilisées pour modéliser Ia synchronisation.

Abstract (Englisch)

Istocheta aldrichi is a tachinid, parasitizing adults of the Japanese beetle Popillia japonica. It is native to Japan and was introduced in the 20th century into North America, where the beetle is also invasive. The project assesses the host specificity of the parasitoid and its potential non-target effects in Switzerland. It also evaluates the climate suitability of Switzerland for establishment of the parasitoids, the host-parasitoid synchronization in the field, and the potential competition with native parasitoids of adult beetles. In 2023, a laboratory rearing of I. aldrichi was established from puparia collected in Canada and has been maintained in the CABI quarantine facility in Delémont since then. No-choice specificity tests were done in 2023 and 2024 with field-collected beetles native to Switzerland. In total, 16 non-target beetle species were tested, from which five were accepted for oviposition, but only two were suitable for development. From thousands of non-target beetles that were inspected in North America, one species was identified as possibly bearing eggs from I. aldrichi. Phenological data of the beetle in the Ticino and of the fly in Canada were used to develop a phenology model, which predicts a generally good synchrony of the parasitoid-host system under Swiss climate conditions, unless unusually warm locations and years are encountered. No larval or adult parasitoids adopting P. japonica as a new host in Switzerland were found.