Dr Helen Nahrung1, Dr Angus Carnegie2, Dr Firehiwot Eshetu3, Dr Katrin Fitza3, Prof Irene Barnes3, Prof Bernard Slippers3

1Forest Research Institute, University of The Sunshine Coast, Dutton Park, Australia, 2Forest Science, NSW Department of Primary Industries, Parramatta, Australia, 3Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa

Biography:

Helen is a senior forest health research fellow at the University of the Sunshine Coast. She is very pleased to be back in Hobart, where she started her career in forest health with a PhD in forest pest management in the CRC for Sustainable Production Forestry at University of Tasmania in 2003. She has since worked in hardwood and softwood plantations in the subtropics, and in biocontrol, biosecurity and invasion biology.

Abstract:

Tasmania was the first Australian state in which the invasive softwood pest Sirex noctilio (Sirex) (Hymenoptera: Siricidae) established and was the site of first releases of the mycetophagous-parasitic nematode, Deladenus siricidicola, for its biological control. Following severe Sirex outbreaks in Victoria in the late 1980s attributed to a mass-rearing-induced loss of virulence in D. siricidicola, the re-isolation of nematodes from Tasmania’s Kamona Forest became a globally acclaimed biocontrol success story. Kamona-strain nematodes were introduced to South Africa and to countries in South America where Sirex is also invasive. In Australia, Kamona-strain nematodes are produced commercially and inoculated into felled trees in an augmentative biocontrol program costing >$0.5M per year. Inoculation effectiveness is measured by assessing parasitism rates in woodwasp populations, indicating the persistence of nematodes in subsequent generations. While occasional regionalised outbreaks have occurred, Sirex has generally remained at low population densities since the Kamona strain was introduced, and nematodes are consistently found in background populations. Internationally, concerns have been raised about the sustainability of the biocontrol program because of extreme homozygosity in nematode populations and variable parasitism influenced by biotic and abiotic factors. Unexpectedly, molecular characterisation of nematodes from Sirex populations in Tasmania, Victoria, New South Wales and South Australia found the Kamona strain represented <20% of samples; a previously unknown strain (“Lineage D”) was dominant. This lineage has been confirmed as a sterilising strain, has high genetic diversity and a higher reproductive rate than Kamona and is being considered for incorporation into the biocontrol program.