Rapid preliminary characterisation of host specificity of leaf-beetles (Coleoptera: Chrysomelidae)

Abstract

Rapid characterisation of host specificity is important both in biological control of weeds and studies in ecology and evolution. A means for doing this was developed and tested on four species of leaf beetles of interest for biological control of the weed Mimosa pigra (Mimosaceae). We identified the most promising for the more detailed tests necessary to obtain release approval. The impact of time-dependent effects and effects of experience were also investigated as part of this study but were not detected. Short-term host specificity tests on adult feeding accurately predicted the results of longer term trials. The long-term trial showed that survival on a plant species depended on feeding on it. Hence short-term feeding trials can predict the longer term survival of adults on other plant species. Different feeding results were obtained in cut foliage versus entire plants but no consistent pattern was shown: of the two insect species tested, one species ate more of the cut material while the opposite was demonstrated for the second species. Species in order of priority for further consideration as biocontrol agents were Syphrea bibiana, Genaphthona sp., Syphrea sp. and Paria sp. The latter three species were probably not sufficiently specific for release. The tests done here allow the identification of the most likely species upon which to conduct the more laborious and difficult larval developmental tests, saving considerable resources.

Keywords:

• biological control
• host specificity testing
• host range determination
• leaf-beetles
• Chrysomelidae

We wish to express our sincere thanks to the following people: David Briese, Tony Willis, Bob Pemberton, and Peter Harris for commenting on the manuscript; Anne Bourne for providing statistical advice; David Furth and Gerhard Scherer for identifying Syphrea spp. and Genaphthona sp.; Wills Flowers for identifying Paria sp.; Arelí Mira, Leonie Wittenberg, Sounthi Subaaharan, and Ryan Zonneveld for providing technical assistance; Wendy Forno, Ken Harley, Ricardo Segura, Moises Martinez, John Winder, Jair da Silva, and Cesar Garcia for collecting and sending insects from Tropical America to Australia; and Environment Australia for providing financial support.