Oak wilt, caused by the fungal pathogen, Bretziella fagacearum (Bf) has the capacity to kill red oaks (group Lobatae) within 6 weeks of infection and its presence across 24 states in the US has resulted in the death of thousands of red oak trees. Bf is vectored by nitidulid beetles when spore-laden insects visit fresh wounds on healthy trees. To determine the high-risk periods of infection, we are examining the periods and the duration of spore production, contaminated insect activity, and tree susceptibility. Additionally, we are working to improve and optimize molecular detection methods and conduct a population genomic study to understand how Bf has spread across the US. Three field sites in the lower peninsula of Michigan were surveyed at two-week intervals from April to November 2018 for the presence of sporulating mycelial mats, spore carrying nitidulid beetles, and symptomatic trees. Mature red oak trees have been inoculated and monitored twice a month at each site throughout this time period. Results to-date indicate that sporulating mats are produced during the spring, summer, and fall. Peak periods of insect vector activity overlap with spore availability in late spring and early summer. Inoculated trees succumb to infection until early October. Results of the on-going field and lab experiments will be used to determine the key risk periods of Bf transmission, which may influence the timing of activities such as pruning that cause tree wounding.