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You’ve prepared y our c ommunity for:

You’ve prepared y our c ommunity for:. Dutch Elm Disease. You’ve prepared y our c ommunity for:. Oak Wilt. You’ve prepared y our community for:. Emerald a sh borer. But… . What a bout BOB?. Prepare Your Community for B ur O ak B light: BOB. Bur Oak Blight: the details.

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You’ve prepared y our c ommunity for:

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  1. You’ve prepared your community for: • Dutch Elm Disease

  2. You’ve prepared your community for: • Oak Wilt

  3. You’ve prepared your community for: • Emerald ash borer. But…

  4. What about BOB? Prepare Your Community for Bur Oak Blight: BOB

  5. Bur Oak Blight: the details • Fungal foliar disease (leaf spot) • Tubakiaspecies complex found in Europe and Asia • Bur oak-specific

  6. What Does it Look Like? Note wedge-shaped blotches

  7. Is it in Minnesota? • Yes • Confirmed in 3 counties • Hennepin • Mille Lacs • Sherburne

  8. BOB is found in a limited area Bur oak distribution is in green and the area with reported BOB occurrences is circled in red USDA, NRCS. 2011. The PLANTS Database (http://plants.usda.gov, 25 February 2011). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

  9. New find? • Symptoms noticed in upper Midwest since 1990s • Symptoms have increased in recent years • First symptoms recorded from southern MN • Minnesota DNR Forest Health Specialist found late-season disease attacking bur oaks

  10. What Trees are Affected? • Only bur oak - to date

  11. How Does it Spread?

  12. How Does it Spread? • Spores from infected leaf blades and petioles • Spring infection

  13. 5. Recognizable Symptoms? • Seen after mid-July • Leaves turn brown along veins and in V-shaped areas • Worse at bottom of crown and interior • Slow-spreading but worsens each year • Trees infected one year show symptoms the following year

  14. BOB Symptoms • Leaves fall off after becoming completely brown • During summer, black fruiting structures form along leaf veins and petioles • Can be easily seen with 10X magnifying lens • Leaf symptoms usually more severe on lower crown • Trees infected with BOB susceptible to secondary pests like two-lined chestnut borer and Armillaria root rot

  15. Hosts BOB Symptoms • Unique feature: some (but not all) infected leaves remain on tree during winter; healthy bur oaks shed all their leaves in the fall • Even a small number of leaves hanging on over the winter indicate BOB may be there • Leaf petioles remain intact • Black fruiting bodies forming in late fall are overwintering stage of the fungus • Healthy trees are mixed with dying trees; probably due to variation in resistance

  16. Otherpests affecting bur oak Oak anthracnose Two-lined chestnut borer Oak wilt Joe O’Brien, bugwood.org Steve Katovich, bugwood.org Fred Baker, bugwood.org

  17. Can Anything be Done? • Maintain health: water management, mulch • Chemical injections: Propiconazole

  18. What to do if you see BOB • Contact the Minnesota Department of Agriculture “Arrest the Pest” hotline at 651-201-6684 (metro) or 1-888-545-6684 (toll free) • Contact info also found in the Forest Pest First Detector Manual

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