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Individual Highlight

New tool detects oak wilt fungus faster and more accurately

Photo of Image 1: Obtaining branch sample from white oak for evaluation of new oak wilt diagnostic tool. USDA Forest Service
 
Image 2: Drilling to obtain sapwood shavings for fungal DNA extraction. Image 1: Obtaining branch sample from white oak for evaluation of new oak wilt diagnostic tool. USDA Forest Service Image 2: Drilling to obtain sapwood shavings for fungal DNA extraction. Snapshot : Oak wilt is one of several significant diseases threatening the health of oak trees in the U.S. and is a potential threat worldwide. Accurate and timely laboratory diagnosis is critical to controlling the disease. A Forest Service scientist and collaborator have developed and validated two molecular-based diagnostic tools that greatly exceed standard isolation methods in time required and accuracy.

Principal Investigators(s) :
Juzwik, Jennifer 
Research Location : Multiple municipalities in east-central Minnesota
Research Station : Northern Research Station (NRS)
Year : 2017
Highlight ID : 1233

Summary

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.

Forest Service Partners

External Partners

  • USDA Forest Service Special Technology Development Program
  • University of Minnesota
  • University of Wisconsin
  • arborists and city foresters in the Minneapolis-St. Paul, Minn., metro area

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