Caused by the fungus Ceratocystis fagacearum, oak wilt is causing crown wilt and the death of oaks in 24 U.S. states; it has been particularly destructive in the Upper Midwest and Texas. If left unmanaged, the disease can dramatically alter urban and natural ecosystems. Effective disease management relies on accurate and timely diagnosis of the disease. Working with a University of Minnesota graduate student, a Forest Service scientist has modified molecular protocols for effective and routine use by plant disease diagnostic laboratories. Fungal DNA was extracted from drill shavings taken from the sapwood of red, bur, and white oaks in different stages of oak wilt development. Amplification of the DNA was completed using either nested or real-time polymerase chain reaction methods. Resulting levels of pathogen detection were compared with rates of detection using standard isolation methods. The molecular protocols were superior in detection frequencies compared to isolation for samples from actively wilting bur and white oak trees. The pathogen could only be detected in one-year-old dead branches (bur, white) and main stems (red) of oak species using the new techniques. The molecular assays can be conducted in fewer than two days, compared to 10 to 14 days of incubation required for isolation. University and state agency diagnostic laboratories are using the methods, particularly for problematic samples.