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Vol. 27, No. 4 Fall 2017
11 | GRASSLANDS Fall 2017
Progress Report: Tumbleweed on California’s
Central Coast
by Devii Rao1, Elise Gornish2, Richard Smith3, and Josh Davy4
During California’s recent drought, Central Coast ranchers
observed noticeable increases in the density and distribution of
tumbleweed on dry annual rangelands. Also known as Russian
thistle (Salsola sp.), this plant can create dense monocultures
(Figure 1), threatening agricultural and native ecosystems (Orloff
et al. 2008). Mature tumbleweed plants become dry skeletons and
blow in the wind, lending them the name “tumbleweed”. Although
several control options are available, they are oen too expensive
for most ranchers to implement. Control methods include
mechanical removal, livestock grazing, biological control, and
herbicide (DiTomaso and Kyser 2013). Because of the high cost,
effective control of tumbleweed continues to be a challenge in
both natural and working landscapes. Some local ranchers burn
tumbleweed skeletons to prevent them from catching on fences
or damaging vehicles. However, by the time tumbleweed plants
are dry, seeds have already been dropped, increasing the seed
bank. erefore, the practice of burning only reduces the nuisance
caused by tumbleweed skeletons and does not control the
invasion. Ranchers do not typically treat tumbleweed with
herbicide because the plant can become widespread and is
generally too expensive to control with this method. However,
ranchers have observed that tumbleweed is less dominant in areas
that are moderately grazed, particularly areas grazed into the
summer. Cattle eat tumbleweed when it is small, before it becomes
spiny. us, while livestock grazing is the primary control method
used by ranchers on the Central Coast, tumbleweed continues to
be a management challenge.
To address this emerging ecological and economic issue, a
research project was developed to investigate tumbleweed control
options and assist ranchers in reducing tumbleweed populations,
while improving forage for livestock. e project was replicated on
nine plots, in groups of threes, established on two ranches in San
Benito County, CA, located predominantly on mixed dry annual
1Devii Rao, Livestock and Natural Resources Advisor, University of
California Cooperative Extension. Devii conducts research and is an
educator in livestock and range management in San Benito, Monterey,
and Santa Cruz counties.
2Elise Gornish, Restoration Ecology Specialist, University of Arizona
Cooperative Extension. Elise conducts research state-wide in a variety of
ecosystems, with an emphasis on arid and semi-arid rangelands.
3Richard Smith, Vegetable Crop & Weed Science Advisor, University of
California Cooperative Extension. Richard has many years of experience
in weed management on row crops on California’s Central Coast.
4Josh Davy, Livestock, Range, & Natural Resources Advisor, University
of California Cooperative Extension. Josh focuses on practical research
to assist ranchers in Tehama, Colusa, and Glenn counties. continued next page
Figure 1. Tumbleweed skeletons on ats and on the slopes in the distance.
Fall 2017 GRASSLANDS | 12
continued next page
grassland, oak savanna, and chaparral, and covering
atlands to steep rugged slopes. e terms “replicate”
and “plot” are used interchangeably here. e term
“subplot” refers to 2.5 m x 2.5 m portions of a plot that
received a particular treatment (Figure 2). Average
annual precipitation at nearby Pinnacles National Park
is 16.55 inches (Western Regional Climate Center
2016).
is project was initiated to test four hypotheses: 1)
moderate cattle grazing will reduce tumbleweed cover,
2) herbicide (a combination of Telar and 2,4-D) will
kill tumbleweed plants, thereby reducing seed
production and tumbleweed cover, 3) seeding with
native grasses will increase competition for
tumbleweed and limit its ability to germinate and
establish, and 4) seeding with non-native forage grasses will
increase competition for tumbleweed and limit its ability to
germinate and establish. Salsola sp., Hordeum murinum L. (wall
barley), non-native bromes, and Erodium sp. (laree) were
common species in plots at the start of the experiment. No native
grasses were observed in the plots. ree replicates (1–3) on
Ranch A are on Mocho loam, 2–9% slopes; three replicates (4–6),
0.58 miles away in the same eld on Ranch A, are on Docas clay
loam, 2–9% slopes; and three replicates (7–9), under separate
ownership on Ranch B, are on Sorrento silt loam, 0–2% slopes.
Each replicate (Figure 2) has a fenced ungrazed section, paired
with a grazed section. Two strips are located within each section:
one received an herbicide treatment and the other received no
herbicide (Figure 3). Both treatments were split into 2.5 x 2.5 m
subplots that receive no seeding, native seed mix, or forage seed
mix treatments (Figure 2).
e herbicide treatment was applied March 22, 2016 at Ranch A
and April 4, 2016 at Ranch B using a backpack sprayer at 2.0 oz/ac
of Telar XP combined with 4 pt/ac of 2,4-D DMA. Treatment
subplots were seeded (excluding unseeded controls) on November
8, 2016. On the same day prior to seeding, 2% v/v of Roundup
PowerMax was sprayed on herbicide
treatment subplots to limit competition
for the native and forage mix seeding.
Native subplots were seeded with a mix of
Elymus glaucus Buckley (blue wild-rye),
Bromus carinatus Hook. & Arn.
(California brome), and Poa secunda J.
Presl (Nevada blue grass), and forage plots
with Festuca arundinacea Schreb. (Flecha
tall fescue, a cultivar). E. glaucus Buckley
and B. carinatus Hook. & Arn. seed was
donated by Hedgerow Farms (Yolo Co.);
P. secunda J. Presl seed was collected in
San Benito County by Bureau of Land
Management staff; and F. arundinacea
Schreb. was donated by L.A. Hearn Seed
Company (Monterey Co.).
Tumbleweed
continued
Although it can be difficult to establish native grass species, E.
glaucus Buckley and B. carinatus Hook. & Arn. were chosen
because they are fairly robust and may compete with tumbleweed
for space (Seabloom et al. 2003). Poa secunda J. Presl was added
to the mix because although it is a much smaller-statured grass, it
may establish better and recruit more successfully long-term than
the other two native species in the dry local environment (R.
O’Dell, pers. com.). F. arundinacea Schreb. was chosen as the
forage treatment because it is robust and may compete well with
tumbleweed considering its successful establishment and
persistence in long-term studies (e.g. Davy et al. in press).
e native and forage mixes were seeded into sub-plots by hand.
B. carinatus Hook. & Arn., E. glaucus Buckley, and P. secunda J.
Presl were seeded at 10, 10, and 5 pounds per acre, respectively
(see Koukoura and Menke 1995). Seed from all three species were
mixed and seeded together in each native seeding plot for a total
seeding rate of 25 pounds per acre. F. arundinacea Schreb. was
seeded at a rate of 10 pounds per acre. B. hordeaceous L. (so
chess) will be added to the forage seeding plots in the fall of 2017.
Figure 2. Plot layout illustrating one replicate with an ungrazed section and a
grazed section. Each replicate has 12 subplots, six in the ungrazed section and six
in the grazed section.
Figure 3. Ungrazed tumbleweed plot. No herbicide on the left. Herbicide treatment on the right.
13 | GRASSLANDS Fall 2017
Because B. hordeaceous L. is an annual grass, it is expected to out-
compete the perennial F. arundinacea Schreb. erefore, F.
arundinacea Schreb. was seeded in year one to allow it to establish
before seeding B. hordeaceous L. On March 29, 2017 2 pints/acre
of 2,4-D DMA were sprayed in the herbicide treatment subplots
to reduce competition from broad leaves that had already
germinated.
A second set of plots were deployed at the request of Ranch A to
test the hypothesis that herbicide treatment later in the season will
also provide tumbleweed control. ese plots were located in an
adjacent eld to replicates 1–6 from the original experiment. e
herbicide treatment was conducted on May 27, 2016, about two
months aer the original treatment (Figure 4). Replicates for this
experiment are 3 m by 10 m (Figure 5). All replicates were grazed
(unfenced). A mix of 1.3 ounces/ac of Telar XP combined with 4
pints/ac of 2,4-D DMA was sprayed using a backpack sprayer.
In spring 2017, species composition and percent cover data were
collected from all plots (from both experiments) using standard
methods in an aerial survey. e data have not yet been analyzed,
but based on initial observations, the 2016–2017 rain year has
been a good one: Annual grasses that were already on-site,
primarily Hordeum murinum L. and Bromus spp., have grown
dense and tall, and appear to have limited the ability of
tumbleweed to ourish. Some native and forage plants that were
seeded did germinate, but are generally quite low in cover at this
time. Stay tuned for initial results in 2018!
References
Davy J., T. Turri, K. Dykier, andE.S. Gornish. In Press. “Seeded forages
for California annual rangeland.” California Agriculture.
DiTomaso, J.M., G.B. Kyser, et al. 2013. Weed Control in Natural Areas
in the Western United States. Weed Research and Information Center,
University of California. 544 pp.
Koukoura, Z., and J. Menke. 1995. “Competition for soil water between
perennial bunch-grass (Elymus glaucus BB) and blue oak seedlings
(Quercus douglasii H. & A.).” Agroforestry Systems, 32(3):225–235.
O’Dell, R. 2016. Personal communication, 7/27/2016. Mr. O’Dell is a
Natural Resources Specialist with the Bureau of Land Management.
Orloff, S.B., D.W. Cudney, C.L. Elmore, and J.M. DiTomaso. 2008.
“Russian thistle: Integrated pest management in the landscape.” UC
IPM Pest Note. Accessed May 12, 2017.
http://ipm.ucanr.edu/
PMG/PESTNOTES/pn7486.html
Seabloom, E.W., W.S. Harpole, O.J.
Reichman, and D. Tilman. 2003. “Invasion,
competitive dominance, and resource use by
exotic and native California grassland
species.” Proceedings of the National
Academy of Sciences. 100(23):13384–13389.
Soil Survey Staff, Natural Resources
Conservation Service, United States
Department of Agriculture. 2017. “Web Soil
Survey.” Accessed May 12, 2017.
https://websoilsurvey.sc.egov.usda.gov/
Western Regional Climate Center. 2016.
“Monthly climate summary for 01/01/1937
to 05/31/2016.” Accessed May 12, 2017.
http://www.wrcc.dri.edu/cgi-
bin/cliMAIN.pl?ca6926
Tumbleweed
continued
From left: Figure 4. Herbicide treatment on the late-season spray plots. Figure 5. Plot layout for late-season spray experiment. This illustration
represents one replicate. All replicates are grazed (unfenced).
Pacific
Restoration
Group, Inc.
PO Box 429 Perris, CA 92572
951.940.6069
