Our research

A leaf feeding beetle (Gratiana boliviana) has been successfully employed as a weed biological control agent against tropical soda apple in Florida USA where the insect has proven to be host specific and effective in providing control of this weed. Although the insect has been extensively tested for its safety in the USA against native and agriculturally important Solanaceae (such as potato, tomato and eggplant) it had not been host tested against native Australian Solanaceae. It was therefore not known if this leaf-feeding beetle is a viable option for release into the Australian environment.

Current research

The purpose of our project was to determine if the leaf feeding beetle (Gratiana bolviana) is suitable for use as a biological control for tropical soda apple in Australia. The project assessed if the beetle will be safe for release into the Australian environment by determining if it will harm other species In Australia, in particular those that are closely related to tropical soda apple. To do this the project imported the beetle from Florida USA and conducted host testing against native Australian Solanaceae plant species and related families, in quarantine facilities in Australia. During this testing some feeding and limited oviposition and incomplete development was observed on a few native Australian Solanum species.

Plans for the future

This project has resulted in the development of a strong collaboration with the University of Florida. We intend to maintain this collaboration to undertake additional risk analyses. Further research is required to better quantify the risk to closely related native Australian Solanums within the Leptostemonum subgenus. Phylogenetic assessments of relationships between Australian native Solanums would be useful as this data will help to ensure we select native species for future testing which are closely related to those on which we have observed some feeding and limited oviposition and development. Further open field specificity testing will also help to better quantify risk associated with G. boliviana. We also intend to investigate if any of the other insects identified during previous native range surveys on tropical soda apple might be promising for future risk assessments in collaboration with the University of Florida.

A collaboration with the University of Queensland has also been established with the aim to genetically screen leaf samples of tropical soda apple collected in Australia, South America and the southern USA. The aim of this screening is to ensure that the genetics of the invasive population present in Australia is like that present in the USA, and to possibly determine the origins of the Australian populations of tropical soda apple. Screening of populations in this way enables us to determine the potential efficacy of any future biological control programme on this weed.

Collection of leaf samples of tropical soda apple for genetic study.