1) Thousand Cankers Disease is caused by the walnut twig beetle carrying the fungus Geosmithia morbida, which kills black walnut trees. 2) Heat treatments above 52°C for 30 minutes and methyl bromide fumigation at 120 mg/L at 4.5°C for 48 hours were shown to eliminate the beetles and fungus from logs. 3) While insecticides showed promise for preventing beetle colonization, more research is needed to identify effective and practical treatments.

1. Thousand Cankers
Disease Mitigation
Scott Myers, USDA APHIS, Buzzards Bay, MA
Jackson Audley, UT, Knoxville, TN
Bud Mayfield, USDA Forest Service, Asheville, NC
Adam Taylor, UT Knoxville, TN

2. Thousand Cankers Disease
• Walnut Twig Beetle
(Pityophthorus juglandis) +
Geosmithia morbida
• Native to southwest (Blackman
1928, Bright 1981)
• Arizona Walnut (Juglans
major) original host (Tisserat et
al. 2009, Uty et al. 2013)

3. TCD in black walnut native range, Knoxville, TN 2010 (Grant et al. 2011)
G. morbida
recovered, but
not WTB

4. TCD: Signs and Symptoms
• Galleries + Cankers
• Not systemic
• Sever nutrient flow
• Top-down dieback

5. Thousand Cankers Disease: Symptoms

6. Threat to Black Walnut
• Valuable hardwood
o > $500 billion (Newton & Fowler 2009)
o Veneer logs = $$$ (Moltzan 2011)
• Quarantine restrictions  industry concerns

7. Objective
• Evaluate treatments for efficacy in eliminating the walnut twig beetle
and Geosmithia morbida from small black walnut logs
o Heat
o Debarking
o Methyl Bromide Fumigation

8. Wood Acquisition 2012
• June, cut 5 trees symptomatic for TCD
• Clusters of 90 cm bolts + pheromone lure, sticky cards
• Hung in crowns of sympt. trees at 9 locations for 2 months
• Distributed 30 cm bolts among treatments using beetle card catch
data

10. Heat and Debarking
• Thermocouple depths
o 1 cm into sapwood
o Core
• Temp. recorded every 1 min
• Logs reaching treatment temp at 1 cm
exposed for at least 30 min, removed in 10
min batches (exposure 30-40 min)
1 cm
core

11. Pathogen Analysis
• 3 bark samples removed per log
and examined for cankers
o 2011: pre- and post-heat
o 2012 post-heat
• Chips surface sterilized and plated
on PDA

12. Insect Emergence
• Bolts placed in
ventilated plastic
containers at room
temp.

13. Proportion of bolts (n=10 per treatment) positive for Geosmithia morbida
Heat and Debarking 2011: Pathogen Results

14. Heat 2012: Pathogen Results
Proportion of bolts (n=30) positive for Geosmithia morbida and other fungi after
heating to various minimum temperatures for 30-40 min.

15. Heat Treatment 2012: Mean number of walnut twig beetles
emerged per bolt (n=30).
• Why 1 beetle
recovered from 1
bolt treated at 56°C?
• Survived the
treatment (unlikely)
• Dead near bark
surface and
dislodged within
container
• Landed on bolt
between the kiln and
the container

16. control 32 48 64 80
0.01
0.1
1
10
100
1000
WTBemergence/bolt
Methyl bromide initial dose (g/m2)
Walnut twig beetle emergence (mean ± se) following Methyl bromide
fumigation at 5°C for 24 hours.
Fumigation 2012: Beetle Results
(448.9)
A B B C
(0.0)
D
(5.8)
(1.5)
(0.8)

17. Proportion of bolts positive for Geosmithia morbida after fumigation with
various doses of methyl bromide at 5°C and 15°C for 24 hrs.
Fumigation 2011: Pathogen Results

18. Fumigation: Pathogen Results
Proportion of bolts positive for Geosmithia morbida after fumigation with
methyl bromide at 5°C for 48 hrs (10 bolts / treatment × 3m reps).
(0) (0)

19. Confirmatory Pathogen Fumigation: 2013
Proportion of treated and control bolts
positive for Geosmithia morbida post
treatment.
N =41
N =151
Single treatment of was
evaluated at 5C over 48h to
confirm efficacy of the 120
mgL-1 dose.
G. morbida was cultured out of
several samples, indicating
treatment was not 100%
effective 0
0.2
0.4
0.6
0.8
control MeBr (120 mg/L)
2014: Treatment rate doubled to 240 mgL -1 and
still G. morbida recovered from one sample!

20. Pest Dose
(g/m2)
Duration
(hrs)
Approx CxT
(h*g/m2)
Pine shoot
beetle
64 4 220
WTB 80 24 1,400
EAB 112 24 1,580
Pine logs to
China
120 16-24 1,800
G. morbida 240 72 ?
Oak logs 240 72 ~12,000
Methyl bromide fumigation schedules for logs at 5 °C

21. Jackson Audley: Masters Project
Objectives:
1. Identify potential pathways of walnut twig
beetle (WTB) in treated black walnut (J. nigra)
logs and lumber
2. Identify potential treatments to prevent WTB
colonization of logs.
3. Identify potential pathways of WTB in black
walnut nursery stock

22. • Phytosanitation for TCD:
1. Steam heat: 52°C for 30 min (Mayfield et al. 2014)
2. Methyl bromide fumigation: 120 mgL-1 at 4.5 °C for 48 hr
3. Kiln-dried lumber, 100% bark removed
• Industry motives: veneer logs & bark on lumber
Post-Treatment Assays: Can WTB
colonize treated logs and lumber?

23. Extreme Exposure Scenario  5 treatments
1. Steam heated
2. methyl bromide fumed
3. kiln-dried lumber with
bark (KDLB)
4. kiln-dried lumber no
bark (KDLNB)
5. control

24. Materials & Methods – Lumberyard
Exposure Scenario
KDLB
KDLNB
Steam
Control
• 4 treatments:
o Steam Heat
o Control
o KDLB - Bark
o KDLNB – No Bark
• Site: Holston River Farm
• 2 Transects:
o A = with WTB Lure
o B = no lure
Steam
Control
KDLNB
KDLB

25. Results – Extreme Exposure Scenario

26. Results – Extreme Exposure Scenario
Mean (±SE) gallery lengths per treatment Mean (±SE) life stages per treatment
ANOVA: F2, 87 = 44.70; P < 0.001 ANOVA: F2, 87 = 6.30; P = 0.003

27. Results – Lumberyard Exposure Scenario
Circular
Plot Block Est. # from Source Bolt
Supp.
Releases
Total est.
Pressure
1 A 82 40 122
2 A 46 40 86
3 A 48 40 88
4 A 1686 40 1726
5 A 56 40 96
6 B 7 40 47
7 B 137 40 177
8 B 112 40 152
9 B 26 40 66
10 B 210 40 250
Total 2810
Total estimated beetle pressure per plot. Total from source bolts
plus supplemental releases

28. 0
5
10
15
20
25
30
35
Control A Control B Steam A Steam B KDB A KDB B KDNB A KDNB B
NumberofSamples/Beetles
Total number of samples attacked and mean (SE) emergence
by treatment by block
Samples Attacked Emergence
Results – Lumberyard Exposure Scenario

29. Can an insecticides prevent WTB colonization?
• Four treatments:
1.Azadirachtin “Neem” (AzaSol® AI 6%)
2.DOT “Borate” (Tim-Bor® AI 98%)
3.Permethrin (Astro® AI 36.8%)
4.Water (Control)

30. Materials & Methods

31. Results: Insecticide Treatment Efficacy
0
20
40
60
80
100
8hr 24hr 32hr 48hr 56hr 72hr 96hr 120hr
CumulativeMortality%
Azadirachtin 0.003% DOT 15%
Permethrin 0.5% Water

32. 0
20
40
60
80
100
12hr 22hr 36hr 44hr 58hr 72hr 96hr 120hr
CumulativeMortality%
Azadirachtin 0.013% DOT 30% Permethrin 0.5% Water
Results: Insecticide Treatment Efficacy

33. Conclusions
• Topical insecticides promising
• Permethrin = effective
• DOT (30%) = maybe
• Azadiractin = not effective
• Future tests
o Other chemicals labeled for use on logs
o Reduced permethrin rate
o DOT “foam” – increased concentration

34. • Transport of live plants = major pathway
of introduction for TCD?
• Will WTB colonize black walnut nursery
stock? 1. No-choice Assays
2. Choice Assays
Nursery Stock: Risk of TCD

35. No-choice Assays
• Trial 1: 5 sources
• Trial 2: 3 sources – NC,
MO, OH
• 4 diameter classes – A)
0.5-0.8; B) 0.8-1.1;
C)1.1-1.6; D)>1.6
~10 beetles caged on each seedling 5M:5F

36. Nursery Stock– Choice Assays
• Seedlings from 5 sources
• Trial 1 – 4 June to 19 August 2014
• Trial 2 – 20 August to October 17
2014
2 m
2 m

37. No-choice Assays: Number of Attacks
A
A
A
A
a
a
a
a
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
A B C D A B C D
Trial 1 Tial 2
NumberofAttacks/100cm2
ANOVA: F3,32 =
0.68, P = 0.57
ANOVA: F3,32 = 1.10,
P = 0.36

38. No-choice Assays: % Attack
A
A
A
A
a
a
a
a
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
A B C D A B C D
Trial 1 Tial 2
NumberofAttacks/100cm2
A
AB
AB
B
a
ab
ab
b
0
10
20
30
40
50
60
70
80
90
100
A B C D A B C D
Trial 1 Tial 2
PercentofSeedlingsAttacked
ANOVA: F3,32 = 3.74, P =
0.021
DSCF: P = 0.026

39. No-choice Assays: Probability of Attack
X2 = 7.31, P = 0.007
Max adj. R2 = 0.31 X2 = 6.73, P = 0.010
Max adj. R2 = 0.25

40. Results – Choice Assays
Trial 1 Trial 2
Plot
# Est. Beetle Pressure Plot # Est. Beetle Pressure
1 33 1 186
2 103 2 115
3 89 3 45
4 44 4 334
5 86 5 143
6 62 6 108
7 67 7 66
8 112 8 85
9 60 9 149
10 443 10 91
Total 1099 Total 1322
No trees attacked in either trial

41. Conclusions
• WTB can attack nursery stock, no-choice
o All diameter classes attacked – prefer >1.5 cm (Seybold et al. 2010)
o No emergence observed, dead larvae found
• No attacks observed in choice setting
o No interest? – perimeter traps catch low 23 & 41 per trial
o Confounded by exposure method – source as sink?

42. Summary: Treatments
• Debarking
o Not effective – doesn’t remove included bark.
• Insecticides
o Have some potential but more products and efficacy data needed
o Limited practicality
• Heat
o Kiln, ISPM15 and firewood schedules all adequate to mitigate risk of spreading TCD
in wood products.
• Fumigation
o Beetles are killed at relatively low rates (>80 mgL-1 at 5  C for 24h)
o G. morbida will require a schedule similar to oak wilt for quarantine level control (~
240 mgL-1 at 5C for 72 h).
• Vacuum –Steam
o Has good potential, but limited efficacy data and infrastructure

43. Acknowledgements
 Robert Camp
 Andy Tait
 Paul Merten
 Bill Klingeman
 Sian Bailey
 Dillion Alley
Thank You!