Bosque Ecosystem Monitoring Program Tamarisk Leaf Beetle Monitoring
May-August 2013
Introduction
The tamarisk leaf beetle (Diorhabda spp.) was released by the U.S. Department of Agriculture as a
biological control agent for Tamarix spp. (often referred to tamarisk or saltcedar) in Nevada, Utah,
Colorado and Wyoming in 2001 and in Texas in 2004 (Knutson et al., 2009). Tamarisk is a nonnative tree introduced to the U.S. in the 1800’s (Sher, 2013). The initial cause of concern about
tamarisk was the amount of water it was thought to consume (Cleverly, 2013). However, its risk as
a fire hazard and regrowth after fires at the expense of native species have become more of a
concern. Tamarisk serves as a ladder fuel (Steuver, 2000), burns intensely, and resprouts well after
fires (Glenn and Nagler, 2005).
In 2007, the Tamarisk Coalition partnered with other
agencies to track the expansion of the beetles, which were
thought not to survive below the 38th parallel (Minard,
2011). This location, which includes the bottom third of
Colorado and Utah and south, is significant because in
this area, tamarisk is potential habitat for the endangered
Southwestern Willow Flycatcher (Sogge et al., 2008).
Thus, agencies are tracking tamarisk leaf beetle migration
in this area, their impacts on tamarisk trees and
Southwestern Willow Flycatcher numbers.
The beetle migrated to Arizona in 2009 and New Mexico
in 2010 (Tamarisk Coalition, 2012). In May 2013, the
Bosque Ecosystem Monitoring Program (BEMP)
partnered with the Tamarisk Coalition, Northern Arizona
University and the U.S. Army Corps of Engineers to track
tamarisk leaf beetle populations at 22 of its 27 sites,
ranging from Santo Domingo Pueblo in the north to
Lemitar (near Socorro) in the south (Figure 1). Four of
the five sites not sampled contain no tamarisk; Mesilla,
the southernmost site, was not monitored.
Figure 1: Tamarisk leaf beetle presence at
BEMP sites from May to August 2013
Goals of this monitoring were to determine how fast the beetles are spreading, the change in its
population, its effect on tamarisk and the effect of these beetles on the Rio Grande riparian
ecosystem. A longer-term goal was to see what happens after tamarisk dies or tamarisk cover is
reduced. For instance, will native willows (preferred historical habitat of the Southwestern Willow
Flycatcher) grow inside tamarisk skeletons as they did in Colorado (A. Sher, Associate Professor at
University of Denver, personal communication); or will other invasive exotic species take
advantage of the available habitat?
1 Methods
The week of the third Tuesday in May, June, July and August 2013, BEMP sites were surveyed for
tamarisk leaf beetles using methods based on Tamarisk Coalition protocols. Five tamarisk trees at
least five meters apart were sampled using sweep nets (Photo 1). Five sweeps were taken from each
tree. After sampling each tree, net contents were emptied into labeled plastic bags (Photo 2), and
photographs were taken of the trees to track defoliation over time. The same trees and photo points
were visited each month. BEMP staff and University of New Mexico (UNM) interns, in addition to
some middle and high school students, collected field samples.
Contents of the plastic bags were processed in the lab by BEMP staff and UNM interns using a
dissecting scope. Quantities of adults, early larvae and late larvae tamarisk leaf beetles were
counted, as were splendid tamarisk weevils (Coniatus splendidulus), tamarisk leafhoppers (Opsius
stactogalus), spiders and ants. Other arthropods present were counted and identified to order. We
paid specific attention to the weevils because they were also considered as a biological control agent
but were not deliberately released because of concern over the impact to “sensitive and endangered
species” (Eckberg and Foster, 2011). Leafhoppers play an important role because they are
competitors of the tamarisk leaf beetle (Gould, 2008). Finally, spiders and ants are predators of the
tamarisk leaf beetle (Gould, 2008).
Photo 2: UNM interns empty contents of the net into a plastic
bag
Photo 1: BEMP staff samples for
tamarisk leaf beetles
Results
In May, tamarisk leaf beetles were present at seven of the 20 sites monitored, including Santo
Domingo and six sites in Albuquerque between Alameda Blvd and Rio Bravo (Figure 2). Santo
Domingo had the highest number of beetles, with 11 adults. Albuquerque sites only had one to two
2 beetles present; all were adults except for one larva. Little to no impact was seen on any tamarisk
monitored, even at Santo Domingo (Photo 3), which had the greatest number of beetles.
Figure 2: Tamarisk leaf beetles were present at seven BEMP sites in May 2013.
In June, tamarisk leaf beetles were present at 11 of the 22 sites1 monitored, including Santo
Domingo, Santa Ana, seven sites in Albuquerque between Alameda Blvd and I-40 and two sites in
Belen (Figure 3). Again, Santo Domingo had the highest number of beetles, at 179. Dominance
shifted from mostly adults in May to mostly larvae in June. There was little defoliation to the trees
at Santo Domingo (Photo 4) or any other site.
In July, tamarisk leaf beetles were present at 13 of the 22 sites monitored, including Santo
Domingo, eight sites in Albuquerque between Alameda Blvd and I-40, Bosque Farms, Los Lunas
and Belen (Figure 4). Two sites in central Albuquerque had the highest number of beetles; Montaño
had 362, and Savannah had 223. Adults dominated the population, but a number of larvae were
present. There was defoliation to tamarisk at Santo Domingo (Photo 5), Diversion, Minnow,
Montaño, Savannah, Route 66, RGNC and Reynolds Forest and Reynolds Clear.
1
Two sites in Albuquerque (Calabacillas and BioPark) were not sampled in May but were sampled in June
and July. Four trees were added to the Los Lunas sample in June and July; only one tree was sampled in
May.
3 Figure 3: Tamarisk leaf beetles were present at 11 BEMP sites in June 2013. Note shift in scale of y-axis.
Figure 4: Tamarisk leaf beetles were present at 13 BEMP sites in July 2013. Note shift in scale of y-axis.
4 Photo 3: Santo Domingo tamarisk #5 May 2013
Photo 4: Santo Domingo tamarisk #5 June 2013
Photo 5: Santo Domingo tamarisk
#5 July 2013
Photo 6: Santo Domingo tamarisk #5
August 2013
In August, tamarisk leaf beetles were present at 15 of the 22 sites monitored, including Santo
Domingo, Santa Ana, nine sites in Albuquerque between Alameda Blvd and Rio Bravo, Los Lunas,
two sites in Belen and Lemitar, just north of Socorro, NM (Figure 5). Santa Ana had the greatest
number of beetles, at 558 – the highest number for the season. There were mostly adults, with a few
larvae present. Tamarisk trees were highly defoliated at Santo Domingo, Santa Ana, Diversion,
Minnow, Montaño, Savannah, Route 66, RGNC and Reynolds Forest and Reynolds Clear (e.g.,
Santo Domingo, Photo 6).
5 Figure 5: Tamarisk leaf beetles were present at 15 BEMP sites in August 2013. Note shift in scale of y-axis.
For the entire sampling season (May to August), tamarisk leaf beetles were present at 19 of the 22
sites sampled (Figure 6). At two of the three sites where the beetles were not obtained through
sampling (Reynolds Forest and Reynolds Clear), tamarisk trees were visibly defoliated (Photo 7);
our sampling did not determine whether the defoliation was caused by tamarisk leaf beetles or
tamarisk leafhoppers.
The abundance of splendid tamarisk weevils (Figure 7),
tamarisk leafhoppers (Figure 8), spiders (Figure 9) and
ants (Figure 10) varied across sites during the sampling
period. No significant correlation, positive or negative,
existed among the abundance of tamarisk leaf beetles
and abundance of weevils, leafhoppers, spiders or ants.
Photo 7: Tamarisk defoliation at the Reynolds Forest site in July 2013. 6 Figure 6: Tamarisk leaf beetles were found at 19 of the 22 BEMP sites sampled from May to August 2013.
Figure 7: Abundance of splendid tamarisk weevils varied across sites from May to August 2013.
7 Figure 8: Abundance of tamarisk leafhoppers varied across sites from May to August 2013.
Figure 9: Abundance of spiders varied across sites from May to August 2013.
8 Figure 10: Abundance of ants varied among sites from May to August 2013.
Discussion
We were informed that tamarisk leaf beetles were present at the Pueblo of Santa Ana in 2010
(Nathan Schroeder, Restoration Division Manager at the Pueblo of Santa Ana, personal
communication) and in Albuquerque in 2012 (Ondrea Hummel, Ecologist at the U.S. Army Corps
of Engineers, personal communication). Our monitoring officially documented the beetle in 2013 at
BEMP sites where tamarisk is present; these data are being used by the U.S. Army Corps of
Engineers in collaboration with Northern Arizona University via the Tamarisk Coalition. We will
continue monitoring to determine the change in beetle, weevil and leafhopper abundance; impact to
tamarisk, both short- and long-term; tamarisk recovery time; tamarisk mortality; and potential
impacts to Southwestern Willow Flycatcher habitat. In addition, BEMP will monitor reestablishing
vegetation and thus track changes in native and exotic cover.
References
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American West. A. Sher and M.F. Quigley (eds). Oxford University Press: New York, NY.
Eckberg, J.R. and M.E. Foster. 2011. First Account of the Splendid Tamarisk Weevil, Coniatus
splendidulus Fabricus, 1781 (Coleoptera: Curculionidae) in Nevada. The Pan-Pacific Entomologist
87(1):51-53.
9 Glenn, E.P. and P.L. Nagler. 2005. Comparative Ecophysiology of Tamarix ramosissima and
Native Trees in Western U.S. Riparian Zones. Journal of Arid Environments 61:419-446.
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http://www.ars.usda.gov/Research/docs.htm?docid=6937
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http://allaboutwatersheds.org/library/inbox/2012_TLB_Distribution_Map.pdf
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