Biosurveillance of oak wilt disease in Canadian areas at risk

Biosurveillance of invasive species is critical for protecting native ecosystems and limiting economic losses. Early detection of pathogens through qPCR methods has recently shown great promise and can potentially slow the spread of devastating diseases. For instance, oak wilt, a disease caused by the fungus Bretziella fagacearum, can kill mature trees within weeks of infection. Originally contained in the United States, oak wilt has finally made its way into Canada, where it was recently observed for the first time in June 2023. This study has laid the foundations for a biosurveillance monitoring program of B. fagacearum in Eastern Canada. From 2019 to 2021, insect vectors were baited and captured in Lindgren traps in various locations of interest, namely sawmills importing oak logs from the United States (US), forested areas containing mature oak trees and strategic sites along the border between the two countries. Insect vectors and collection fluids were analysed with our qPCR detection test for the presence of B. fagacearum. As a positive control to validate this method, we included traps in a known centre of oak wilt infection in Michigan (US). Our analysis showed only one positive site at the border between Ontario (CA) and the US, even though oak wilt has never been observed there. This result confirms that DNA from B. fagacearum can be detected with this method even before the appearance of symptomatic trees, which could be crucial in the current containment efforts in Ontario (CA).