1. Minnesota First Detectors Thousand Cankers Disease What is it? Where is it? Why do we care? What should we be do about it now? Kathleen Alexander, City Forester, Boulder, CO

2. Minnesota First Detectors 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 Why do we care? Because if it spreads eastward, it may threaten native eastern black walnut in several states What should we do about it now? Be aware - recently discovered, still many unanswered questions

3. Minnesota First Detectors Juglans susceptibility - Tentative LeastModerateVery Arizona walnut (Juglans major) Northern California black walnut (J. hindsii) Eastern black walnut (Juglans nigra) planted outside native range Little walnut (Juglans microcarpa) California black walnut (Juglans californica) Eastern black walnut (Juglans nigra) Native range ????? English walnut (Juglans regia) ??? Butternut (Juglans cinerea) ??? Thousand Cankers Disease What is it? A disease of some walnut trees (Juglans species) Two occur in Minnesota – J. cinerea, J nigra

4. Minnesota First Detectors 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 Whitney Cranshaw, Colorado State University, Bugwood.org

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

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

7. Minnesota First Detectors Thousand Cankers Disease What is it? 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. Minnesota First Detectors Thousand Cankers Disease Where is it? Counties Confirmed Counties Suspected As of October 6, 2009 Fowler & Newton, USDA-APHIS, 10.19.2009 Only area where native black walnut are dying

9. Minnesota First Detectors Thousand Cankers Disease Why do we care? Because the insect/fungus complex seems to have spread outside the native range of its original host To other areas and other hosts Range of original host, Arizona walnut Juglans major

10. Minnesota First Detectors Thousand Cankers Disease Why do we care? Eastern black walnut native range Counties Suspected or Confirmed Fowler & Newton, USDA-APHIS, 10.19.2009 Because eastern black walnut in its native range may be threatened if the disease spreads eastward

11. Minnesota First Detectors Thousand Cankers Disease Why do we care? Because the native range of eastern black walnut includes southeast Minnesota We harvest about 1.35 million board feet (2700 cords) of walnut annually Vasievich & Kinglsey 1995

12. Minnesota First Detectors Almost 30% of Minnesota’s walnut is exported to other states annually, mainly Wisconsin and Iowa. There are about 40 mills in Minnesota that use walnut. About 12% of the walnut milled in Minnesota is imported annually, mainly from Wisconsin and Iowa. Bark is usually on. Thousand Cankers Disease Why do we care?

13. Minnesota First Detectors At this time there are many unanswered questions about the disease so we don’t really know if our resource is threatened. e.g. Can the walnut twig beetle and its fungus survive in Minnesota? Some states (Indiana, Kansas, Missouri, Nebraska) are drafting exterior quarantines for walnut moving out of states with Thousand Cankers Disease. Minnesota is not pursuing new regulations at this time. Thousand Cankers Disease What should we be doing now?

14. Minnesota First Detectors PathwayEstimated approach rate based on USDA APHIS Pathway Assessment 2009 TimberLow: walnut production low in west; little timber shipped from west to east FirewoodLow to moderate: through firewood distributors, long distance campers Wood packing material (WPM) Low to moderate: WPM with most domestically shipped commodities, 1.2 billion pallets in circulation Nursery stockLow: No reports of infested nursery stock Scion woodLow: Walnut breeding programs in west have revised practices to prevent spread Natural spreadLow: Walnut twig beetle flies 1-2 miles; may be carried by wind because of its small size Thousand Cankers Disease What should we be doing now? Be aware of the potential pathways for spread

15. Minnesota First Detectors 6,494,041 black walnut trees Thousand Cankers Disease What should we be doing now? Outreach, especially in southern and southeastern Minnesota Mill owners Loggers Tree care companies First Detectors Early detection? No lure at this time, may be available in 1-2 years Learn more