Response to the detection of Fusarium dieback associated with ambrosia beetles on Acer negundo in New South Wales

Symptoms consistent with polyphagous shot hole borer (Euwallacea fornicatus) and Fusarium dieback (Fusarium euwallaceae), recognised as high priority environmental pests for Australia, were observed on a single box elder (Acer negundo) tree in Sydney, New South Wales, in March 2022 during routine forest biosecurity surveillance. Delimiting surveys were undertaken around the Sydney basin, extending radially from the original box elder, resulting in the detection of a further three box elder and one tuckeroo (Cupaniopsis anacardioides) with suspicious symptoms. Samples were taken from the five trees and associated beetles diagnosed using morphological and molecular methods. Associated Fusarium-like fungi were identified according to phylogenetic inference using regions of the internal transcribed spacer, as well as the translation elongation factor 1-alpha and RNA polymerase II genes. The tea shot hole borer, Euwallacea perbrevis, was identified along with its known fungal mutualist, Fusarium obliquiseptatum. This pair have been reported in Queensland on avocado (Persea americana) and tuckeroo, and there are unpublished records of E. perbrevis from northern NSW, but this is the first report of both species occurring simultaneously in NSW. The biosecurity response following the initial detection, including the establishment of an Incident Management Team, surveillance, diagnostics, and stakeholder engagement, is discussed. This paper highlights the importance of surveillance for early detection of invasive pests and biosecurity systems and processes for enabling a timely response.