Understanding Thousand Cankers Disease: Threats and Prevention Strategies

1. Thousand Cankers Disease • What is it? • Where is it? • Why do we care? • What should we do? Kathleen Alexander, Boulder, CO

2. Thousand Cankers Disease • What is it? A disease of some walnut trees that is caused by an insect and a fungus • Where is it? In western and southwestern areas of the United States; in Tennessee • Why do we care? Because as it spreads eastward, it threatens native eastern black walnut • What should we do? Prevention: reduce risk of introduction

3. www.plantcare.com/.../black-walnut-2127.aspx Thousand Cankers Disease: What is it? A disease of some walnut trees (Juglans species) • Two occur in Minnesota Butternut (Juglans cinerea): Unknown susceptibility Eastern black walnut (Juglans nigra): Very susceptible www.plantcare.com/.../black-walnut-2127.aspx • www.tree-pictures.com/butternut_tree_photos.html

4. Thousand Cankers Disease: What is it? • ….. caused by a tiny insect that feeds and tunnels in the inner bark of the trunk and branches Walnut twig beetle Pityophthorus juglandis Tunneling Entry / exit holes Whitney Cranshaw, Colorado State University, Bugwood.org W. Cranshaw , Colorado State Univ. www.forestryimages.org

5. Thousand Cankers Disease: What is it? • The walnut twig beetle introduces a fungus - Geosmithia morbida • that kills the bark and phloem, causing a canker Jim LaBonte, OR Dept. Agric. Whitney Cranshaw, Colorado State University, Bugwood.org “Canker: A visible dead area, usually of limited extent, in the cortex or bark of a plant.” (Tainter & Baker, 1996) Ned Tisserat, Colorado State University

6. Thousand Cankers Disease: What is it? • Cankers coalesce, eventually girdling and killing the branch or trunk Ned Tisserat, Colorado State University

7. Thousand Cankers Disease: What is it? Crown symptoms: Yellowing & wilting foliage, followed by branch dieback & death may occur in susceptible species Kathleen Alexander , City Forester, Boulder, CO Whitney Cranshaw, Colorado State University

8. Thousand Cankers Disease: Where is it? States in red & Tennessee Confirmed July 2010 Original host, Arizona walnut Juglans major

9. Thousand Cankers Disease: Where is it? KY MO • Black walnut dieback for 2+ years. • TCD confirmed July 2010. • TCD confirmed in 4 counties. • Surveys initiated in neighboring states. VA NC 1st report in native range Knoxville, TN Source: M. Mielke NCFPW 2010 MS AL GA Urban settings news.tennesseeanytime.org/node/5926

10. Thousand Cankers Disease: Why do we care? …because it threatens eastern black walnut in its native range & there is no control

11. Thousand Cankers Disease: Why do we care? 5.9 million

12. Thousand Cankers Disease: Why do we care? • In Minnesota • 5.9 million trees (Winona, Wabasha, Fillmore Counties each have > 1 million black walnut trees) • Annual state harvest – • 1-2 million board feet • 0.1% volume of all wood harvested • $3 million • 5% of $60 million total stumpage value for all wood harvested • 30% exported, mainly to Wisconsin, Iowa • 40+ mills in Minnesota use walnut;12% imported, mainly from Wisconsin and Iowa; bark on.

13. Thousand Cankers Disease: Why do we care? Other impacts • Ecologic • Harder to measure • Nuts as food for wildlife • Important species of riparian corridors • Bark used for medicine, dye • Social • Culture around walnuts for food

14. Thousand Cankers Disease: What should we do? PREVENTION • Minimize the risk of introduction • MOST IMPORTANT PATHWAY • = • Wood with bark: • logs for veneer • pieces for woodworking • firewood Natural spread: Walnut twig beetle can fly 1 – 2 miles, and be carried by wind

15. Thousand Cankers Disease: What should we do? Tools for prevention • Regulation • Outreach • Early detection

16. Thousand Cankers Disease: What should we do? Regulation • Who regulates? • Infested western states No • APHIS No • Eastern states Yes

17. Thousand Cankers Disease: Regulation State Quarantines Exterior quarantines Exterior quarantines ? In progress In progress Interior quarantine Source: E.Borchardt, MN Dept. Agric.

18. Thousand Cankers Disease: What should we do? Outreach! • Newsletters, websites • Telephone, email, visits • Presentations • TO • Partner organizations • Mill owners, loggers • Landowners • Tree care companies • Nurseries Photos courtesy of Mike Greenheck, Forest Field Day , Gorman Creek Farm, Kellogg, MN, October 2010

19. Thousand Cankers Disease: What should we do? Early Detection • First detector training • MDA/USFS survey for suspect trees: Call Arrest the Pest Hotline 651-201-6684 1-888-545-6684 OR follow instructions on survey form to contact Jennifer Juzwik, USFS 651-649-5114 jjuzwik@fs.fed.us Kathy Kromroy, MDA 651-201-6343 kathryn.kromroy@state.mn.us

20. Early Detection: Does your black walnut have TCD? • Early symptoms (late June to late August) Tree may be infested 6-8 years before see crown symptoms Area of thinning crown Yellow or wilting leaves Attached brown leaves Leaves smaller than healthy leaves

21. Early Detection: Does your black walnut have TCD? • Actively declining symptoms Rapid wilting Cankers on branch below wilting foliage Reducedlive crown on trees affected previous season

22. Early Detection: Does your black walnut have TCD? • Late symptoms • Many tiny holes on branches >1.5 inches • Galleries and meandering tunnels • Small cankers in inner bark if scrape away outer bark • Large dead areas on branches & stems

23. Early Detection: Does your black walnut have TCD? • What else may be confused with Thousand Cankers Disease? • Nectria cankers Fusarium cankers -similar decline Anthracnose • Other beetles Hail injury, storm damage • Squirrel girdling of branches

24. Acknowledgements • Jenny Juzwik, Mike Ostry, Paul Castillo. USFS Northern Research Station. • Manfred Mielke. USFS State & Private Forestry. • Keith Jacobsen, Lance Sorenson.MN DNR. • Mike Greenheck. Gorman Creek Farms, Kellogg MN. • Mel Baughman, Angie Gupta. UM Extension.