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HOST COLONIZATION
AND FLIGHT PATTERNS OF
THE WALNUT TWIG BEETLE
IN NEW MEXICO
Corwin Parker UC Davis Dept. of Entomology & Nematology
Study Goals
Determine the flight periodicity of WTB in its native range across an
elevational gradient and between two local host species
Determine the attack density and productivity of WTB among different
Juglans species
Investigate Differences in WTB host preference between CA and NM
populations
Flight Pattern Study
Host Preference Study
Nematode Study
Investigate nematodes found inside WTB and within WTB galleries
Are WTB-associated nematodes parasites, phytopathogens or other?
Pityophthorus juglandis
Walnut Twig Beetle
Stacy Hishinuma, UC Davis Andy Graves, USDA FS
WTB + Geosmithia morbida
Thousand Cankers Disease
Ned Tisserat, CSU
Geosmithia morbida creates oblong cankers in the phloem around beetle
galleries. The cankers often coalesce and kill the branch
TCD damage
Photo credit: Ned
Tisserat and
Whitney Cranshaw,
CSU
Crown dieback and epicormic sprouting are evident in advanced cases of
TCD. Photo of Juglans major in Lincoln County, New Mexico.
TCD damage
Photo credit: Corwin
Parker
Native walnut distributions
NM study site
Walnut and TCD distributions
NM study site
*
*
Determine the flight periodicity of WTB in its
native range across an elevational gradient and
between two local host species
Flight pattern study
Twelve traps were set up along a transect starting in the Sierra Blanca Mountains
of New Mexico near Ruidoso (elev. 2300 m) and running eastward along U.S.
route 70 to the desert near Roswell (elev. 1200 m)
Study Site
Figure credit: Andy
Graves
Methods
Flight traps used were 4-unit Lindgren funnel traps, baited with synthetic WTB
aggregation pheromone
Collection cup filled with antifreeze
Flight Traps
Photo credit: Steven
Seybold
Methods
Traps were emptied weekly from April through December, 2013, and from
January to the present, 2014
Flight Traps
Photo credit: Steven
Seybold
Methods
WTB were sorted each week and both sexes were counted and stored in
ethanol
Sorting
Sometimes other insects got in the way
Photo credit:
Joe Boggs
Corwin Parker
Methods
Highest elevation flight trap in trapping transect, illustrating trap located 3-5
m from an old growth J. major in a mixed oak-conifer forest.
Juglans major
Photo credit: Corwin
Parker
Methods
Low elevation site in the trapping transect, illustrating trap located next to a
multi-stemmed J. microcarpa in an open desert riparian habitat.
Juglans microcarpa
Photo credit: Corwin
Parker
Methods
Results: Flight Patterns By Time
0
100
200
300
400
500
600
700
800
900
1000
WTB tra
pped
NM1
NM2
NM3
NM4
NM5
NM6
NM7
NM8
NM8.5
NM9
NM10
NM11
Trap name
2013 2014
Two major flight peaks per year, separated by dry season during June (red arrows)
California Flight Patterns 2012-13
0
20
40
60
80
100
120
Results: Flight Patterns By Elevation
Discussion
In New Mexico and California, WTB has two major flight peaks during the year
The first flight peak likely represents the emergence of overwintering adults and larvae that develop in the spring
The second flight peak likely represents adults that have developed early from the current year’s brood
Greater WTB flight activity at the higher elevation sites
Greater flight activity associated with J. major
Lower flight activity at the highest elevation sites due to low host density?
Determine the attack density and productivity of WTB
among different Juglans species
Investigate differences in WTB host preference between
CA and NM populations
Host Preference Study
California: Wolfskill Experimental Orchards, USDA ARS National Clonal
Germplasm Repository, Winters, Solano County, California
California Study Site
Photo credit: Stacy
Hishinuma
Methods
Fort Stanton Snowy River Cave, National Conservation Area, Lincoln County
New Mexico Study Site
Photo credit: Corwin
Parker
Methods
All studies included J. major, microcarpa and hindsii, as well as 2-3 other
walnut or related species
10 branches per species per trial
18 branches per species in the 2014 NM trial
Tree Species
J. nigra
Eastern black walnut
J. microcarpa
Little black walnut
J. major
Arizona walnut
J. californica
Southern CA black
walnut
J. hindsii
Northern CA black
walnut
J. regia
English walnut
J. cinerea
Butternut
P. stenoptera
Chinese wingnut
C. illinoinensis
Pecan
Methods
Completely randomized design
Juglans tree
(J. major in NM, J. hindsii in CA)
Baited branch
Branch Set-up
New Mexico study site set-up
2013 2014
California study site set-up
Methods
Photo illustrating a branch trap with J. hindsii with pheromone bait pinned to
the bottom
Branches were left in field for 2-3 weeks, after which all entrance holes were
counted
Branch Set-up
Photo credit: Corwin
Parker
Methods
After branches were removed from field, they were cut in half and placed in
ventilated rearing cages
Rearing Cages
Photo credit: Corwin
Parker
Methods
Every week emerged adults were removed from cages and the sexes were
counted
Parental vs brood adults
Emerging Adults
Photo credit: Corwin
Parker
Methods
Response of WTB to Five Hosts in the Field, Wolfskill
Experimental Orchards, California, August, 2012
a
b
bc
a
c 0.00
0.02
0.04
0.06
0.08
0.10
J. hindsii J. major J. microcarpa P. stenoptera C. illinoinensis
Mean a
ttack
s/cm
²
CA Aug 24 - Sept 7, 2012
a
b
b b
c
1
10
100
1000
10000
J. hindsii J. major J. microcarpa P. stenoptera C. illinoinensis
Mean b
rood
CA Sept 7, 2012 - April 6, 2013
Kruskal-Wallis Test;
χ² = 41.571; DF = 4; P<0.001
ANOVA on transformed
(data = log(brood+0.1));
F=57.18; DF=4; P<0.001
Attack Density Productivity
Response of WTB to Five Hosts in the Field, Wolfskill
Experimental Orchards, California, May, 2013
ab
bc bc
a
c
0.00
0.05
0.10
0.15
0.20
0.25
J. hindsii J. major J. microcarpa J. nigra J. regia
Mean a
ttack
s/cm
²
CA May 24 - 31, 2013
a
b
b
a
b
1
10
100
1000
10000
J. hindsii J. major J. microcarpa J. nigra J. regia
mean b
rood
CA May 31 - Dec 2, 2013
Kruskal-Wallis Test; χ²= 25.9645;
DF=4; P<0.001
ANOVA; F=31.83;
DF=4; P<0.001
Attack Density Productivity
Response of WTB to Six Hosts in the Field, Wolfskill Experimental
Orchards, California, September, 2014
a
ab
ab
a
ab
a
0.00
0.05
0.10
0.15
0.20
0.25
J. hindsii J. major J. microcarpa J. nigra J. californica J. cinerea
CA Sept 22 - Oct 14, 2014
Kruskal-Wallis Test;
χ²=21.9121; DF=5; P<.001
Attack Density
Response of WTB to Five or Six Hosts in the Field, Wolfskill
Experimental Orchards, California, 2012-2014
a
b bc
a
c 0.00
0.05
0.10
J. hindsii J. major J. microcarpa P. stenoptera C. illinoinensis
Mean a
ttack
s/cm
²
CA Aug 24 - Sept 7, 2012
a
b b b
c
1
10
100
1000
10000
J. hindsii J. major J. microcarpa P. stenoptera C. illinoinensis
Mean b
rood
CA Sept 7, 2012 - April 6, 2013
Attack Density Productivity
ab
bc bc
a
c
0.0
0.1
0.2
J. hindsii J. major J. microcarpa J. nigra J. regia
Mean a
ttack
s/cm
²
CA May 24 - 31, 2013
a
b b
a
b
1
10
100
1000
10000
J. hindsii J. major J. microcarpa J. nigra J. regiam
ean b
rood
CA May 31 - Dec 2, 2013
a ab ab
a
ab
a
0.0
0.1
0.2
0.3
J. hindsii J. major J.microcarpa
J. nigra J. californica J. cinerea
Mean a
ttack
/cm
²
CA Sept 22 - Oct 14, 2014
Response of WTB to Four Hosts in the Field, Fort Stanton, New
Mexico, June, 2013
ab
a
b
a
1
10
100
1000
J. hindsii J. major J. microcarpa J. nigra
Mean b
rood
NM: July 18 - Dec 2, 2013
Kruskal-Wallis Test; χ²=25.7180;
DF=4; P<.001
ab a
b
a
0.00
0.01
0.02
0.03
0.04
J. hindsii J. major J. microcarpa J. nigra
Mean A
ttack
s/cm
²
NM June 25 - July 17, 2013
PROC GLMMIX; F=4.72;
DF=3; P<0.01
Attack Density Productivity
Response of WTB to Five Hosts in the Field, Fort Stanton, New
Mexico, August, 2014
Kruskal-Wallis Test;
χ²=25.7180; DF=4; P<.001
c
bc
ab
a
ab
0.0000
0.0100
0.0200
0.0300
J. hindsii J. major J. microcarpa J. nigra J. californica
Mean a
ttack
s/cm
²
NM Aug 17 - Sept 10, 2014
Attack Density
c
bc
ab
a
ab
0.0000
0.0100
0.0200
0.0300
J. hindsii J. major J. microcarpa J. nigra J. californica
Mean a
ttack
s/cm
²
NM Aug 17 - Sept 10, 2014
Response of WTB to Four or Five Hosts in the Field, Fort Stanton,
New Mexico 2013-2014
ab
a
b
a
1
10
100
1000
J. hindsii J. major J. microcarpa J. nigra
Mean b
rood
NM: July 18 - Dec 2, 2013
ab a
b
a
0.00
0.01
0.02
0.03
0.04
J. hindsii J. major J. microcarpa J. nigra
Mean A
ttack
s/cm
²
NM June 25 - July 17, 2013
Attack Density Productivity
Discussion
• Attack density on J. nigra highest in both states
• J. hindsii had higher attack rate in CA
• Higher WTB population density in California site
may have led to higher attack densities
• Variation in NM 2014 may be due to branch quality
Synthesis
WTB flight patterns similar outside of native range
Higher attack rate on local trees in both CA and
NM
Eastern black walnut and butternut highly preferred
by WTB
Explains rapid spread of WTB through Western
USA
Suggests extremely high expansion potential for
Eastern USA
Investigate nematodes found inside WTB and within their
galleries
Are WTB-associated nematodes parasites,
phytopathogens or other?
Nematode Study
1. Branches from CA and NM walnut trees were dissected
2. Gallery tissue was placed in a Baermann funnel for 12-18 hours
3. Aliquots of liquid containing nematodes were transferred to clean water
4. Representative nematodes were heat-killed, photographed, analyzed by PCR (18S) and
sequenced
Nematode extraction and PCR
Photo credit: Corwin
Parker
Methods
Results
Several nematode morphospecies isolated from
WTB and galleries
Morphological analysis: Tylenchs and Cephalobs in
CA, Rhabdites in NM
Nematodes found in the beetles appear to be 1st
instars, with mostly adults in the galleries
Poor sequencing results
More work needs to be done describing the
nematodes morphologically and molecularly
Acknowledgments
Thank you:
Steven Nadler
Steven Seybold
Yigen Chen
Paul Dallara
Andy Graves
Stacy Hishinuma
Ivana Li
Irene Lona
Scott McCluen
Bruce Moltzan
Institutions: USDA Forest Service, WO Forest Health
Protection and FHM Programs
USDA Forest Service Lincoln National Forest, Smokey Bear Ranger District
USDA ARS National Clonal Germplasm Repository
UC Davis Department of Entomology and Nematology
