Prioritisation of pest species for biosecurity risk assessments: using plant-parasitic nematodes and Australia as examples

Three species were chosen for CLIMEX modelling to cross-validate their biosecurity risks to Australia. Two of the species”Heterodera zeae and Meloidogyne graminicola”were the highest risks identified by the PeST framework, and the other”Hirschmanniella oryzae”had the highest SOM index but ranked only 20th using the PeST framework. The models were carefully parameterised with species phenology and global distributions obtained from peer reviewed literature. Rain-fed and irrigation scenarios were included to simulate possible different field conditions. The projected species distributions from CLIMEX were concordant with all available experimental and field observations with only a few exceptions. All three species had high eco-climatic and growth index values in Australia (>30), suggesting the biosecurity risks identified by other criteria are real. Maps of host crops (maize, rice, wheat) and irrigation areas in Australia were compared with projected growth index maps of each nematode species to identify areas at risk. Much greater areas were conducive for the growth of the three species under irrigation than under rain-fed conditions, both globally and in Australia. These results show that modified conditions such as irrigation need to be taken into consideration when assessing the establishment potential and biosecurity risks from exotic species.