Host testing, establishment and biology of the gorse soft shoot moth, Agonopterix umbellana (Fabricius) (Lepidoptera: Oecophoridae), a potential biological control agent for gorse, Ulex europaeus L. (Fabaceae), in Australia

Host specificity tests on over 250 species or cultivars of plants including 37 Australian native and introduced plant species or cultivars showed that the gorse soft shoot moth, Agonopterix umbellana, would be unlikely to survive on any plant other than gorse in Australia. The first field release was at Jericho, Tasmania during spring 2007. By the summer of 2013 high larval densities of A. umbellana were evident at the release point, with dispersal recorded to a maximum of 200 m over ca. 2 ha. Recoveries at other release sites in Tasmania as well as in South Australia and Victoria suggest that the species will eventually establish across south-eastern Australia. The life cycle of A. umbellana is closely synchronised with gorse phenology. Population increase and dispersal is expected to be slow as a consequence of its univoltine life cycle incorporating the narrow larval feeding period of 3 months when gorse is a suitable food source. At Jericho, oviposition commenced in late winter which enabled hatching to coincide with the presence of new gorse growth for developing larvae. Larvae fed over a 3 month period on new growth available from mid-October to mid-January passing through six instars before pupation. The first adults were recorded in early February emerging in an obligate reproductive diapause which was completed by late July. Controlled temperature cabinets held at 12, 15, 18, 21 and 24 Celsius degree were used to estimate lower development thresholds (LDT) and thermal constants. The LDT for eggs larvae, pupae and total development were 8.7, 7.5, 7.9 and 7.9 Celsius degree, respectively and the thermal constants were 143.0 , 526.3 , 278.0 and 971.0 degree days respectively. In the long term, it is hoped that A. umbellana will contribute to the biological control of gorse in Australia. This will be in combination with the gorse seed weevil, Exapion ulicis, the gorse spider mite, Tetranychus lintearius and the gorse thrips, Sericothips staphylinus, even though earlier studies have shown these other agents are constrained either by predation in the case of T. lintearius or the effects of gorse phenology in the case of S. staphylinus and E. ulicis.