Northern red oak spring bud phenology linked to oak wilt vector attractiveness to fresh wounds

Oak wilt, caused by the fungus Bretziella fagacearum , is a fungal pathogen fatal to oaks ( Quercus spp.). Species in the red oak group are most susceptible to infection and experience mortality in a short time frame. Oak wilt has been detected in 24 U.S. states. Infected trees were detected, and later removed, from Ontario, Canada. There is risk for further expansion northward, beyond the disease’s current range, which is evident by recent detections in Canada, and Upper Michigan, USA. To better understand the initial timing of host susceptibility in relation to overland spread by nitidulid vector beetles (Nitidulidae: Coleoptera) in northern areas, we investigated relationships between spring bud phenology, nitidulid activity in oak wounds and flight traps, growing degree days, and environmental variables. We hypothesized that spring bud phenology is associated with the timing of Nitidulidae activity in oak wounds, with bud-break and leaf-out influencing wound attractiveness. Nitidulids were collected in fresh wounds beginning at bud-break even though nitidulids were captured in baited flight traps up to 4 weeks before bud-break. Our results suggest that bud-break is a strong indicator of wound attractiveness to nitidulid beetles and could be used as a visual cue to determine the start of the high-risk period. These findings will inform policies for oak wilt prevention, in addition to providing foresters with a visual cue for the high-risk period.