Response to the detection of an exotic fungal pathogen, Fusarium commune, in a Pinus radiata production nursery in Australia

ABSTRACT Early detection of exotic pests is key to a timely response for enabling options for eradication and future management. It is widely recognised that engaging the public and industry in general surveillance significantly increases the chance of detecting newly arrived pests and pathogens. Once a new pest or pathogen is detected, Australia has guidelines to follow via the Emergency Plant Pest Response Deed and PLANTPLAN. This paper describes the detection of unusual symptoms in a Pinus radiata production nursery in New South Wales, Australia, and the subsequent response. The unusual symptoms were detected in early January 2021 by nursery staff and reported immediately to biosecurity authorities. The nursery was placed under quarantine as a precaution. Within five weeks, Fusarium commune was diagnosed from the samples, a known pathogen of conifers not previously recorded in Australia. Formal biosecurity processes were enacted immediately to determine whether the pathogen was an emergency plant pest and whether eradication was necessary and technically feasible. Quarantine and movement restrictions continued, such that no seedlings could leave the site other than for ongoing diagnosis and under biosecure protocols. Tracing was conducted to determine the distribution of the pathogen and a potential source, including ongoing sampling in production nurseries, diagnosis of planting media and seed, and diagnosis of root and soil eDNA samples collected in previous years. Fusarium commune was recovered at a very low frequency from two nurseries, primarily in association with healthy seedlings. Root and soil samples collected from nurseries and plantations between 2019 and 2020 tested negative for the presence of F. commune using F. commune-specific primers. Pathogenicity tests revealed that F. commune did not cause wilting or significant disease on tested seedlings. Overall, evidence suggested that F. commune did not pose a serious threat to the P. radiata industry. The Consultative Committee on Emergency Plant Pests determined that F. commune was not a significant pathogen and that no further action was warranted. The affected nursery was allowed to resume operations in mid-May 2021, in time for the winter planting season. Here we discuss the lessons from this response, including the benefits of a quick and timely response, cross-institutional collaboration, the potential threat to the forest industry, and the need to encourage greater general surveillance. These lessons can help in the event of an incursion of a serious pathogen such as F. circinatum (pine pitch canker).