Jared Whitaker
Public Service Assistant
Area Agronomist
Background
• Grew up in Cordele, GA
• B.S. Biology – Georgia Southern University
(2004)
• Holder Ag Consulting (1999-2005)
M.S. Agronomy – University of Georgia
(2004 - 2006)
– Dr. Craig Bednarz
• Thesis: A comparative agronomic analysis of subsurface
drip irrigation and overhead irrigation in Georgia cotton.
Publications:
Whitaker, J.R., G.L. Ritchie, C.W. Bednarz, and C.I. Mills. 2008. Cotton subsurface drip
and overhead irrigation efficicieny, maturity, yield, and quality. Agron. J.
100:1763-1768.
Ritchie, G.L., J.R. Whitaker, C.W. Bednarz, and J.E. Hook. 2009. Subsurface drip and
overhead irrigation: a comparison of plant boll distribution in Upland cotton.
Agron. J. 101:1345-1351.
Subsurface Drip Irrigation Research in GA Cotton
SSD compared to overhead, sprinkler irrigation
• Required less water to maintain proper soil moisture
• Similar or higher yields
• Higher WUE
• Other effects of SSD irrigation
– SSD matured slightly faster than overhead
– SSD irrigation shifted boll distribution down in plant canopy
From agronomic standpoint, SSD is a viable
irrigation method for cotton in GA
P.h.D in Crop Science – NC State
(2006 - 2009)
– Dr. Alan York
• Dissertation: Distribution, biology, and control of glyphosateresistant Palmer amaranth in North Carolina.
Publications:
Whitaker, J.R., A.C. York, D.L. Jordan, A.S. Culpepper, and L.M. Sosnoskie. 2010. Evaluation of residual herbicides for
control of glyphosate-resistant Palmer amaranth. J. Cotton Sci. IN PRESS
Whitaker, J.R., A.C. York, D.L. Jordan, and A.S. Culpepper. 2010. Palmer amaranth (Amaranthus palmeri) control in
soybean with glyphosate and conventional herbicide systems. Weed Technol. IN PRESS
Whitaker, J.R., A.C. York, D.L. Jordan, and A.S. Culpepper. 2010. Weed Management with Glyphosate- and Glufosinatebased Systems in PHY 485 WRF Cotton. Weed Technol. IN PRESS
Whitaker, J.R., A.C. York, D.L. Jordan, and A.S. Culpepper. 2010. Glyphosate-resistant Palmer amaranth Management in
Cotton. J. Cotton Sci. IN REVIEW
Whitaker, J.R., A.C. York, D.L. Jordan, and A.S. Culpepper. 2010. ‘PHY 485’ Cotton Tolerance to Glufosinate. Weed
Technol. IN REVIEW
Culpepper, A.S., J.R. Whitaker, A.W. MacRae, and A.C. York. 2008. Distribution of glyphosate-resistant Palmer amaranth
(Amaranthus palmeri) in Georgia and North Carolina during 2005 and 2006. J. Cotton Sci. 12:306-310.
Distribution of glyphosate-resistant
Palmer amaranth in NC (2005)
• Resistance in 49 of 290 fields sampled -- 11 NC counties
- 10 fields with high level resistance
- 30 fields with low level resistance
- 9 fields with mixed populations
- * By 2009 found in 11 additional counties (unconfirmed)
Field Work: Management Strategies
• Evaluation of residual herbicides
• PRE herbicides effect on Palmer control
• Total herbicide systems
• Alternative herbicide ystems
Evaluation of Residual Herbicides
a
(Most residual activity)
PRE – flumioxazin (Pre-plant)
pyrithiobac
fomesafen
POST – pyrithiobac or
S-metolachlor
Check
S-metolachlor
Fomesafen
Pyrithiobac
Trif. + prometryn
Flumioxazin
Lay-by – flumioxazin or
trifloxysulfuron + prometryn
(Research from NC and GA)
Preemergence herbicides in a Complete System*
(Late-season)
A
B
A
A
A
AB
BC
B
C
C
AB
A
No PRE
Diuron
Fomesafen
D
% Control
Pyrithiobac**
Fomesafen +
diuron
Diuron +
pyrithiobac**
E
Fomesafen +
pyrithiobac**
2007
2008
*All plots received Glyphosate + S-metolachlor at 1-lf, Glyphosate at 6-lf, and Residual Lay-by
** ALS-susceptible Palmer amaranth
Total system w/ residual herbicides
(2007, Late-season)
B
B
+45%
pts.
+44%
pts.
A
C
D
+35%
pts.
Pre-plant
None
None
Flumioxazin
None
Flumioxazin
PRE
None
None
None
Reflex
Fomesafen
Early-POST
None
Pyrithiobac
Pyrithiobac
Pyrithiobac
S-metolachlor
No residual
1 residual
2 residuals
* All plots received 2,4-D + Glyphosate Pre-plant, Paraquat PRE,
Glyphosate at 2- and 6-lf, and residual Lay-by.
3 residuals
• These glyphosate-based
programs can work well
Glyphosate + 2,4-D burndown
Paraquat + fomesafen PRE
Glyp. + S-metolachlor 1st POST
Glyphosate 2nd POST
Diuron + MSMA Lay-by
• Must have timely rainfall or irrigation to active the PREs and
POST residual herbicides
Palmer amaranth control with Glufosinate
• Glufosinate
– Non-selective herbicide
– Effective on small Palmer amaranth
– Traditionally not as good as glyphosate on Palmer amaranth
and annual grasses
• Glufosinate-based systems could be used to control
glyphoaste-resistant Palmer amaranth in Liberty Link®
cotton
– Poor variety performance (inconsistent yields in SE)
– Growers hesitant to plant these varieties
The Widestrike Cotton Technology and Glufosinate
• Cotton with Widestrike Roundup Ready technologies
– WidestrikeTM is a Bt technology (lepidopteran pests)
– Glufosinate tolerance gene used as selectable marker for
development of Widestrike gene
• Same gene as in Liberty Link, but not selected for glufosinate
tolerance
– Growers more likely to plant these cultivars, also RR
1. Is Widestrike cotton tolerant to Ignite (glufosinate)?
2. Can glufosinate be used to control Palmer amaranth?
Injury in Widestrike Cotton from Glufosinate
(5 and 14 days after application to 4-leaf cotton)
5 days
14 days
Glufosinate 23 oz/A
Labeled Liberty Link rate
Glufosinate 43 oz/A
Max Liberty Link rate
Glufosinate 23 oz/A
Glufosinate 43 oz/A
Effects of Glufosinate (Late June)
Nontreated
Row
IGN 29 oz/A
IGN 29 oz/A + AMS
IGN 43 oz/A
IGN 43 oz/A+ AMS
Widestrike Cotton Tolerance to Glufosinate
– Minor increase in injury with S-metolachlor and pyrithiobac tank-mixes
– No additional injury from mixing various insecticides with glufosinate
– Glufosinate did not affected cotton fiber quality
– Glufosinate negatively affected yield in 2 of 11 trials
– At rates appropriate for Liberty Link cotton,
yield loss occurred in only 1 of 11 (4%)
Widestrike cotton has acceptable tolerance to glufosinate
WHAT ABOUT PALMER AMARANTH CONTROL?
Glyphosate-resistant Palmer amaranth (Mt. Olive, 2007)
Glyphosate- and glufosinate-based systems (Before Lay-by)
Alone
Glyphosate
Glufosinate
POST 1 Tank mix
w/ S-metolachlor
w/ pyrithiobac
Weed control with glufosinate and
glyphosate in Widestrike cotton
• Glyphosate more effective on annual grasses and susceptible
Palmer amaranth
• Glufosinate more effective on resistant Palmer amaranth
• Observed weed control anatagonism of glyphosate when
mixed with glufosinate in:
– Glyphosate-susceptible Palmer amaranth
– Common lambsquarters
– Several annual grass species
Control of glyphosate-resistant Palmer amaranth feasible in
glufosinate-based systems with timely applications
UGA – 2009
• Public Service Assistant
• Area Agronomist
• 100% Extension Appointment
• Cotton
– Extension agronomist (East Georgia)
• Soybean
– Extension soybean agronomist (Statewide)
The Cotton Variety Situation in Georgia
• One variety has dominated GA’s acreage
• DP 555 BG/RR and other single Bt gene varieties will no
longer be available
– Approximately 30% in 2010
– None after 2010
– New varieties on ½ million acres in GA in 2010
• New varieties
–
–
–
–
Being released rapidly $$$$
Experience limited (often no multi-year data)
Yield stability of DP 555 BG/RR?
Do well under good growing conditions in 2009 ……
Cotton Research
• On-farm variety evaluations
– CORE variety trial
– Widestrike and LL variety performance (w/ glufosinate)
• New variety management
– PGR management
• Methods to evaluate new varieties
– Plant mapping
– Maturity classification
• SSD cotton in Georgia
Soybean Research
• Maximizing soybean yields
– Irrigation strategies
– Twin-row soybean production
– Nematode management project
– Stinkbug management project
• Dryland variety evaluation
• Liberty Link soybean production
Thank you