1. Thousand Cankers Disease (TCD)
What is it?
Where is it?
Why is it important?
What are we doing about it?
Declining black walnut
K.Kromroy

2. What is TCD? Disease of walnuts (some species)
Caused by a twig beetle and a fungus together
Ned Tisserat, Colorado State Univ.

3. What is TCD? Two species in Minnesota are affected: Butternut
Eastern black walnut
Several species of walnut are affected by the disease
Arizona walnut (Juglans major), thought to be original host of walnut twig beetle, occurs in southwest United States and Mexico; the twig beetle does not cause major damage, even though it carries the fungus.
Mortality of native California black walnut trees (J. hindsii, J. californica) has been recently observed (work by Steve Seybold and Andrew Graves)
Two Juglans in Minnesota: Eastern black walnut – very susceptible, butternut – unknown, but TCD was confirmed on a butternut growing in Eugene OR in January 2012 – this is the first report of natural infection of the species
The ranges of butternut and black walnut overlap in MN, but butternut occurs farther north

4. What is TCD? Walnut twig beetle (WTB)
Originally associated with Arizona walnut
Feeds on inner bark of trunk and branches
Walnut twig beetle
A minute bark beetle – smaller than a grain of rice
Adults and larvae do extensive tunneling in the inner bark
One of a group of beetles known as “twig beetles” because they normally restrict damage to small diameter twigs and are not a major problem
Which seems true on Arizona walnut, Juglans major, which is likely the original host and occurs in southwest United States
BUT, on black walnut species it is very aggressive, and attacks large branches and the main trunk
All photos Whitney Cranshaw , Colorado State Univ.

5. What is TCD? Fungus carried by beetle; introduced into wounds
Fungus kills the bark and phloem
Causes a canker (dead area below the bark)
Jim LaBonte, OR Dept. Ag.
Thousand Cankers Disease is similar to Dutch Elm Disease and Oak Wilt in that a fungus is carried by an insect and introduced into the tree.
But it is different in that rather than causing a vascular wilt, it causes cankers.
Ned Tisserat, Colorado State University

6. What is TCD?
Cankers grow together, girdling and killing the branch or trunk
Small cankers enlarge and coalesce
Ned Tisserat, Colorado State University

7. Symptoms of TCD Yellowing, wilting foliage Branch die-back, death
Minnesota Dept. of Agriculture
Whitney Cranshaw, Colorado State University
Initial crown symptoms similar to those caused my many other kinds of stress.
Since 2000, many eastern black walnut (Juglans nigra) that were planted as street and landscape trees have died in Colorado, particularly in the cities of Boulder and Colorado Springs.
Yellowing, wilting foliage
Branch die-back, death

8. History of WTB and TCD Prior to 2003
1928
Early 1990’s
2001
2003
Original description of WTB, New Mexico
Report of black walnut mortality, northern New Mexico; WTB associated.
Reports of black walnut decline and mortality in Boulder and Denver, Colorado
Reports of black walnut decline and mortality in Oregon & Utah

9. Original host: Arizona walnut
Where is TCD now?
2012
Original host of insect/fungus complex thought to be Juglans major, Arizona walnut, on which the complex results in very little damage.
It seems that this insect/fungus complex may be “jumping” to other hosts and thus also expanding its geographic range.
REPORTS IN EASTERN US
Original host: Arizona walnut

10. Why is it important?
Threatens all eastern black walnut in its native range
No known control
Native range of butternut overlaps, extends a little further north.
Industry very concerned.

11. Number of Black Walnut Trees over 1″ dbh on Forested Land
Data from USFS Forest Inventory & Analysis - on FORESTLAND
Missouri ranks first in U.S.
Iowa second or third
5.9 million

12. Black walnut moves through Minnesota – hundreds of logs each year
Black walnut logs at rail yard in St. Paul. Origin Iowa, Wisconsin, Illinois, often Minnesota
Hundreds of logs/year
Unloaded from trucks, wait in yard until loaded into containers for rail shipment to west coast then overseas to Asia – for veneer, then back to US
As of 18 January 2013: TCD is prohibited pest under Korea's Plant Protection Act. Impose emergency
import restriction of wood products and plants for planting ofvJuglans spp. to prevent possible introduction of TCD and it's vector into Korea
Required from states with TCD: Heat treatment before shipping - Phytosanitary certificate (PC) should contain the information on heat (same trt regime as below)
Required from states with out TCD:
HT treatment: above 56℃ (core temp.) for 30 min. or
MB fumigation: in accordance with below fumigation schedule
Minnesota Dept. of Ag.
Korea’s new regulations

13. Value of black walnut Social Ecological
Culture around walnuts for food
Bark used for medicine, dye
Ecological
Harder to measure
Nuts as food for wildlife (squirrels, beaver, red-bellied woodpecker
Important species of riparian (riverbank) corridors
Slide from Manfred Mielke

14. What are we doing?
PREVENTION
Education
Regulation
EARLY DETECTION

15. ESTIMATED APPROACH RATE
Education: Pathways of Introduction
PATHWAY
ESTIMATED APPROACH RATE
Timber
Low; little timber shipped from west to east
Firewood
Low to moderate; firewood distributors, long-distance campers
Wood packing
Low to moderate
Nursery stock
Low; no reports of infested nursery plants
Scion wood
Low; programs in west revised to prevent spread
Natural spread
Low; beetle flies 1-2 miles
To prevent introduction, must know the pathways.
Analysis published on 2009 re movement from west to east.
All but one pathway are people
What we know now………..
Another not considered –
Newton & Fowler, 2009

16. Pathway: Wood for Hobbyists
Internet sales
Mail-order companies
Hobby shows
Homeowner in Bucks County taking down trees, most 4-8” dbh, a few much larger.

17. Pathway: Wood for Hobbyists
Black walnut logs, slabs, and burls with bark attached
Walnut orchard in CA, with grafted trees – the graft areas make good wood for hobbyists
Ohio – WTBs caught in traps at mill site that imports walnut burls from CA – no TCD infested trees yet.
Minnesota Dept. of Agriculture

18. Education Presentations Newsletters Websites E-mail notices
Site visits To
Partner organizations
Mill owners
Loggers
Tree care companies
Nurseries
Industry very interested in protecting the black walnut resource
Photos courtesyMike Greenheck

19. Regulation Who regulates the movement of walnut logs?
Infested western states - No
APHIS - No
Eastern states - Yes
Western states – no regulations to prevent movement out of state
APHIS – chose not to regulate because the insect/fungus complex thought to be native to the US
Eastern States have put interior and exterior quarantines into place

20. Regulation
Explain
Interior quarantine – regulates material leaving an infested area
Exterior quarantine – regulates material coming into an area to keep out infested material

21. 2011 Visual surveys in 15 states
Early Detection
USDA APHIS funds
Core CAPS
2011 Visual surveys in 15 states
Map from J. Juzwik, USFS
Federally funded TCD surveys in 15 other states
MN 2011 – 2500 walnut trees visually assessed. 5 branch samples collected –no TCD
MN walnut trees visually assessed around mills or sites previousl id’d and traps at 3 sites A few branch samples. Results pending
MN 2013 – trapping at 10 sites – high risk, millIowa and WI
Two surveys in Minnesota – worked together: MDA – urban, USFS – other areas
Visual surveys – suspicious trees were then sampled and samples processed in state or other selected labs
Data in national database
Forest Service and MDA conducted visual surveys – no TCD found

22. Visual Assessment: Early symptoms
Thinning crown
Yellow or wilting leaves
Tree may be infested 7 or more years before showing crown symptoms
J.Juzwik, USFS

23. Symptoms – oozing cankers
Minnesota Dept. of Ag.

24. Actively declining symptoms
Whitney Cranshaw, CO State University
Limbs die in 1 season
W. Cranshaw Colorado and ___ in TN –hard to find early. In TN – low dieback, mildly symptomatic
Rapid wilting
B.Moltzan, USFS
Top-down dieback

25. Signs Larval galleries Many holes on branches over 1.5″ dbh
photos W. Cranshaw , CO State Univ.

26. Small cankers in inner bark
J.Juzwik, USFS

27. Old cankers under bark on black walnut lose their color
Minnesota Dept. of Ag.

28. Large dead areas on branches and stems
J.Juzwik, USFS

29. What might be mistaken for TCD?
Anthracnose
Fusarium canker
Anthracnose widespread on black walnut in Beaver Creek Valley State Park, 2010
Joseph O’Brien, USFS
J.Juzwik, USFS

30. What else might be mistaken for TCD?
Unknown
Site stress
Tom and Ellie Choinksi near Winona have several black walnuts that are declining, dying. Do not suspect TCD as of August Some could be site stress – high water.
Choinski
J.Juzwik, USFS

31. Insects found on girdled black walnut in Indiana and Missouri:
Other insects
Insects found on girdled black walnut in Indiana and Missouri:
Ambrosia beetles
Weevils
Bark beetles
Similar results in trap catches and branch samples in IA and WI
80% of beetles in MO
Asian ambrosia beetle
Jjuzwik did study to test attraction of stressed walnut to insects. Girdled base of black walnut trees in 2 states. Felled 3 months later, sampled segment from stem and branch – thousands of beetles found
Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org

32. Early Detection: a trap with a lure
Much better than visual survey and crown sampling
Lure available commercially
Develop trapping guidelines
Survey funding?
Lure
2012 Lure avail commercially first time.
MN had traps at 3 sites
2013 – traps at 10 sites
S.Seybold, USFS

33. Management Sanitation Tree removal Proper disposal Bury Burn
Minnesota Dept. of Ag.

34. Management Studies in progress because walnut moves! Treatments tested
Debarked only
Debark + heat
Fumigation – methyl bromide
Insecticides
Protectants
Systemics
Insect Repellent
Results of 2011 studies indicated all heat treatments worked to kill fungus and WTB. Will test more heat trt in 2012
Debarking not practical because too hard to get off all bark – and bad for veneer
Insecticides and repellants – don’t hold breath – requires many applications, for systemics, if just a few WTB already present and caused cankers, those cankers will not move chemical as dead phloem.
Photo by Kathy Keatley Garvey)

35. Questions?