Early detection of Agrilus planipennis using environmental DNA

As a recent pest to Oregon, Agrilus planipennis (Emerald Ash Borer, EAB) stands to decimate native ash tree stands, as it has throughout Eastern USA. As shown in common garden studies, Oregon Ash is extremely susceptible to EAB with expected mortality rates of 99% (Herms 2015). EAB infestations are cryptic, and traditional monitoring relies on advanced infestations and costly tree girdling and bark peeling, resulting in appropriate responses lagging the leading edge of the infestation. Environmental DNA (eDNA), the practice of collecting and identifying traces of DNA left in an environmental sample, is a promising tool for early infestation detection and has previously been used to detect EAB in frass samples (Kyei-Pokuet al. 2020, Kyle et al. 2024). Yet, a fast and inexpensive method for eDNA collection is lacking. Prior work found eDNA samples taken with sterilized paint rollers reliably detected Lycorma delicatula (spotted lantern fly, Peterson et al. 2022). Along these lines, the aim of our multiagency project was to determine whether paint rollers could be used to identify EAB infested trees. Using a modified version of the protocol from Peterson et al. 2022, method validation trials have demonstrated the following: 1) eDNA samples from confirmed EAB infested trees return a positive DNA detection; 2) eDNA samples from assumed negative EAB infested trees (outside infestation region) return a negative DNA detection; and 3) Positive DNA detection does not appear to correlate to infestation level, suggesting it may be more correlated to EAB activity level (adult oviposition and larvae emergence).