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Oak Wilt

Oak Wilt. Deadly Pathogen. Oak Wilt. Impacts Distribution, status B iology, identification , and symptoms . Impacts. Serious disease of oaks in the Midwest, eastern US and Texas Attacks all oak species Red oak group (northern pin, northern red, black) is very susceptible

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Oak Wilt

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  1. Oak Wilt Deadly Pathogen

  2. Oak Wilt • Impacts • Distribution, status • Biology, identification, and symptoms

  3. Impacts • Serious disease of oaks in the Midwest, eastern US and Texas • Attacks all oak species • Red oak group (northern pin, northern red, black) is very susceptible • White oak group (bur, swamp white, white) is more tolerant

  4. Distribution of oak wilt Range of oak wilt in Minnesota, 2006 DNR Aerial survey Pine Isanti Range of oak wilt in US Sherburne Anoka Olmsted

  5. Status • In 2011, oak wilt was discovered in St. Croix State Park in Pine County • Most northern find to date • Also found outside the park at a residence • Want to keep it from spreading throughout the oak resource Range of red oak in Minnesota

  6. Biology of oak wilt • Fungal pathogen, Ceratocystisfagacearum • Discovered 1942 in Wisconsin • Now thought to be an introduced pathogen, possibly from Central or South America or Mexico • Spreads in two ways: overland by insects and underground through grafted roots

  7. Biology of oak wilt • Fungus causes a spore mat to form beneath the bark of red oaks after the tree wilts • Pressure pads form on mats that cause bark to crack • Spore mats have a fruit-like odor that attracts sap beetles • Sap beetles pick up sticky fungal spores; fly to healthy but wounded tree; contaminate tree wound with fungal spores

  8. Biology of oak wilt • Most oak wilt is spread by root grafts of oaks within 50-100 feet of each other • The fungus travels through the water-carrying vessels in the roots to a healthy oak • The tree tries to stop the fungus by producing a gummy substance that clogs water vessels • Lack of water flow causes leaves to wilt rapidly and fall off

  9. Symptoms • Tree “flags,” whole branches or parts of crown turn brown • Leaves drop off • Appearance of fungal mats under the bark • Sapwood streaking is not a sufficient diagnostic character • Conclusive diagnosis from a diagnostic clinic such as U of M Plant Disease Clinic

  10. Identification Oak Wilt • Water-soaked appearance • Tree wilts and dies in same season • Fungal mats produced the following season • Leaves fall off Bur Oak Blight • Wedge-shaped lesion between veins • Tree may live for years with symptoms • Dark veins on underside • Leaves hang on

  11. Oak wilt may also be confused with two-lined chestnut borer • Adults attack oaks stressed by drought, defoliation or construction • Symptoms and signs similar to EAB (same genus) • Characteristic pattern of multi-year attack: “Dead, Red, and Green” • Red oak leaves stay on tree (unlike OW) • Check piled wood for exit holes

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