French flies to help south coast farmers in fight against snails

A biocontrol program using Australian-bred parasitoid flies is the new line of defence against the snail pest population on WA’s south coast. The South Australian Research and Development Institute (SARDI) and the University of Adelaide is leading the four-year program which aims to protect south coast crop yields by using a French fly species to eradicate grain pests such as the small pointed snail. The female flesh fly, a biocontrol agent from France, attacks snail pests by laying live larva on the snails’ shells, which then crawl inside and consume the host before emerging as an adult fly. SARDI and CSIRO mass-reared the French fly populations in the early 2000s on South Australia’s Yorke Peninsula. DPIRD research scientist Svetlana Micic said about 1000 flies were released in the South Stirling, Woogenellup and Esperance districts, marking the first release of flesh flies in WA. “Additional releases will be performed over time to boost numbers and maximise the chances of the fly establishing successfully,” she said. “There can be five, six or more generations of flies attacking snails throughout the spring and summer.” Ms Micic said the biocontrol measure would work alongside baiting and strategic paddock management to suppress the snail population. “It will take some time for the flies to establish. Over the next couple of seasons we will perform more releases together with SARDI and then monitor release sites for establishment success and the potential to extend the program to other parts of the WA grain belt,” she said. “While biocontrol is not a silver bullet, it could prove to be a useful tool for growers with high snail populations.” Snail damage in coastal and high rainfall crop areas has increased over the past decade, which is estimated to be costing the WA grains industry more $6 million per annum in lost production and control costs. DPIRD has also recorded a 30 to 40 per cent increase in parasitism levels in suitable habitat for pest snails. SARDI Entomology and University of Adelaide project leader Kym Perry said the biocontrol program formed part of a multi-faceted effort to improve snail management outcomes for grain growers nationally. “Conical snails are a particularly difficult management challenge for Australian grain growers due to their small size, cryptic behaviour and potential to reach large numbers,” he said. “Biocontrol is a longer-term prospect that, once established, can help to provide partial suppression of conical snail populations free to growers as part of a larger integrated management program.” Dr Perry said the project would expand as the flesh fly population grew across the State to tackle pest snail numbers. “The goal of these initial fly releases in WA is to establish local populations of parasitoid flies in the State, which can spread naturally across snail-affected areas over time and, ultimately, become another tool in the management toolbox,” he said. “It’s fantastic to be working together with DPIRD and farming groups Stirlings to Coast Farmers and South East Premium Wheat Growers Association to provide more tools for snail management in the west.”