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Plant Growth Regulators
Effects of trinexapac-ethyl and
acibenzolar-s-methyl on
drought responses in hybrid
bermudagrass fairways
N I C BR O U W E R , M . D. R I C H A RD S O N , D. E . K A RC H E R , A N D J . H . MC C A L L A
Acibenzolar-s-methyl
Plant defense activator that induces systemic
acquired resistance in plants (SAR)
SAR
 Mechanism of induced defense that provides protection against a
broad spectrum of microorganisms
 Associated with the accumulation of pathogenesis-related proteins
 (Durrant, 2004)
Effective against viruses, bacteria, and fungi
Common component of turfgrass management
systems
 Reduce mowing requirements and seedheads
 (McCarty, 2001)
 Enhance stress tolerance
 (Brosnan, 2010)
Trinexapac-ethyl applications can increase drought
tolerance
 (Jiang, 1998)
 (McCann, 2008)
Acibenzolar-s-methyl
Research shows that AB may be responsible for
activating a transpiration-limiting response in
creeping bentgrass
Plots treated with Daconil-Action limited transpiration
under high vapor pressure deficits
 Transpiration control became engaged when VPDs reached
values between 1.39 to 2.50 kPa
 (Shekoofa et al. 2015)
 (Zhang et al. 2005), (Baysal et al. 2003)
Research Objective
Compare the effects of trinexapac-ethyl
applied alone or in combination with
acibenzolar-s-methyl on turfgrass
performance under drought conditions.
(Shekoofa et al. 2015)
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Materials and Methods
Arkansas Agricultural
Research and Extension
Center-Fayetteville, AR
 Captina silt loam
 Experiment repeated in 2013,
2014, 2015
Tifsport Hybrid Bermudagrass
 Mowing height 1.27 cm
Materials and Methods
Drought initiation
 3 days after the second treatment
application
 Irrigation withheld for 14-28 days
 Resumed when control dropped below 40%
turfgrass coverage
Moveable rainout structure used to
restrict rainfall on plots
 Four Season Tools, Kansas City MO
 6 mil polyethylene cover
 91% PAR light transmission
 9.75 x 14.63 m
Four treatment applications made on 21 day intervals
Treatment Application Specifics
Trt. No.
Active Ingredient
A.I. Rate
Treatment Code
g ha-1
1
Untreated Check
2
Trinexapac-ethyl
96
UTC
TE
3
Acibenzolar
Trinexapac-ethyl
32
96
TE+AB (low)
4
Acibenzolar
Trinexapac-ethyl
64
96
TE+AB (med)
5
Acibenzolar
Trinexapac-ethyl
96
96
TE+AB (high)
6
Acibenzolar
32
AB (low)
7
Acibenzolar
64
AB (med)
8
Acibenzolar
96
AB (high)
Data Collection
Clippings collected twice per week
 Plots were not mowed between collection dates
Soil volumetric water content
 Twice a week with a Spectrum Fieldscout TDR
 (7.62 cm depth)
Digital image analysis of turfgrass coverage
 3 times a week during the dry down process
Experimental Design and
Statistical Analysis
Randomized complete block design
 4 replications
Turfgrass Coverage
 Subjected to repeated measures analysis using SAS Proc
Mixed
Fisher’s Protected LSD (α=0.05) used to separate
means
Date x Treatment was significant for each year of
trial
Results
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2013 Turfgrass Coverage
2013 Turfgrass Coverage
80%
40%
2014 Turfgrass Coverage
70%
AB High AB Med AB Low
TE+AB
High
TE+AB
Med
TE+AB
Low
TE
UTC
40%
Summer of 2013 middle of drought cycle
TE+AB
AB Med AB High AB Low
Med
Photo on 7/11/2014, prior to initiating drought
TE+AB
Low
TE
TE+AB
High
Photo on 8/13/2014, 19 days after initiating drought
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2015 Turfgrass Coverage
60%
40%
Photo on 7/8/2015, prior to initiating drought
Why were the 2014 results
different?
UTC TE+AB
Low
TE+AB
Med
AB
High
TE+AB
High
TE
AB
Med
AB
Low
Photo on 7/21/2015, 12 days after initiating drought
Vapor Pressure Deficit
2014-VPD was under 3.5 kPa
during at multiple dates
2013 and 2015
 VPDs were between 4.5 and 5 kPa
Shekoofa et al. (2015) looked at
a max VPD of 3.5 kPa
The lower VPD in 2014 may
have allowed AB’s activation of
the transpiration limiting
response to have a greater
effect on turfgrass quality
(Shekoofa et al. 2015)
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Conclusions
Literature Cited
The delay in the onset of drought stress in bermudagrass
treated with TE suggests that numerous irrigation cycles
might be avoided over a single growing season.
Baysal, O., E.M. Soylu, and S. Soylu. Induction of defense related enzymes and resistance by the plant
activator acibenzolar-s-methyl in tomato seedlings against bacterial canker caused by Clavibacter
michiganensis ssp.michiganensis. Plant Path. 52:747-753.
Results suggest that acibenzolar-s-methyl does not have
a significant effect upon drought responses in hybrid
bermudagrass fairways
 This may have been due to higher vapor pressure deficits
However, considerable water savings might be possible
through the use of PGRs such as trinexapac-ethyl
Brosnan, J.T., A.W. Thoms, G.K. Breeden, and J.C. Sorochan. 2010. Effects of various plant growth
regulators on the traffic tolerance of ‘riviera’ bermudagrass. Hort. Sci. 45:966-970.
Durrant, W. E., and X. Dong. "Systemic acquired resistance." Annu. Rev. Phytopathol. 42 (2004): 185209.
Jiang, H., and J. Fry. 1998. Drought responses of perennial ryegrass treated with plant growth
regulators. Hort Sci. 33:270-273
McCann, S.E., and B. Huang. 2008. Drought responses of Kentucky bluegrass and creeping bentgrass as
affected by abscisic acid and trinexapac-ethyl. J. Amer. Soc. Hort. Sci. 133: 20-26.
McCarty, L.B. Best golf course management practices. Upper Saddles River, NJ: Prentice Hall, 2001.
Shekoofa, A., P. Rosas-Anderson, D.S. Carley, T.R. Sinclair, T.W. Rufty. 2015. Limited transpiration under
high vapor pressure deficits of creeping bentgrass by application of Daconil-Action. Planta (online) DOI
10.1007/s00425-015-2417-y
Zhang, Q., J. Fry, and N. Tisserat. Evaluation of plant defense activators for dollar spot and brown patch
control on creeping bentgrass putting greens. Int. Turf. Soc. Res. J. 10:180-185.
Acknowledgements
University of Arkansas Division of Agriculture
Syngenta Crop Protection
Dr. Richardson
Dr. Karcher
Mr. John McCalla
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