2005 Weed Control Update
(Peanut, Field Corn, Soybeans, Sunflowers)
Dr. Eric P. Prostko
Extension Weed Specialist
Dept. Crop & Soil Sciences
University of Georgia
December 2004
Peanuts





Spartan
Cobra
newer metolachlor formulations
Valor Issues
others issues
Spartan in Peanut

Labeled in 2004
 not in FL








4F formulation
4.8 to 8.0 ozs/A
soil-applied
broadleaf weed control
nutsedge
cotton rotation
concerns
crop injury on lighter
soils
PPO inhibitor
Spartan Rotation Restrictions
Spartan Injury
Cobra in Peanut







Labeled in Fall 2004
postemergence
 6 leaf peanut
 90 day PHI
12.5 ozs/A
broadleaf weed control
a hotter Blazer
tank-mixes with Basagran,
Cadre, Pursuit, Select, 2,4DB
PPO inhibitor
Metolachlor Mysteries?

9 formulations in marketplace

new metolachlors (88% s + 12% r)
 Dual Magnum, Dual II Magnum (Syngenta)
 Cinch (DuPont)

old metolachlors (50% s + 50% r)
 Stalwart, Stalwart C (Sipcam)
 Me-Too-Lachlor, Me-Too-Lachlor II (Drexel)
 Parallel PCS, Parallel (Makhteshim-Agan)
Metolachlor Prices
Dual Magnum
$95/gal
$11.88/pt
($8.16/11 ozs)
Stalwart C*
$65/gal
$8.13/pt
Me-Too-Lachlor
$61/gal
$7.63/pt
*only labeled for use in field corn and popcorn
Tropical Spiderwort
Tropical Spiderwort Response to Dual
Magnum and Stalwart, Grady Co., 2004 - I
100
Control - %
80
89
86
89
82
74
60
*
61
40
20
0
9 DAT
29 DAT
Time
Applied PRE at 1 pt/A.
43 DAT
Dual Magnum
Stalwart
Tropical Spiderwort Response to Dual
Magnum and Stalwart, Grady Co., 2004 - II
100
80
89 87
88 89
89 86
Control - %
78
72
60
64
*
51
40
Dual Magnum
Stalwart
20
0
9 DAT
21 DAT
29 DAT
41 DAT
92 DAT
Time
Applied POST at 1 pt/A with glyphosate to 3” tall COMBE.
Valor Issues: Is that hose clean?
Line in Glyphosate
Tank/Line Rinsate
Valor and Sprayer Cleanup
Which plot had AMS?
(Both had Cadre at 1.44 ozs/A + Agrioil @ 1% v/v applied 24 DAP)
PE-08-04
July 1 ,2004
28 DAT
Which plot had AMS?
PE-08-04
August 3, 2004
54 DAT
403
404
Field Corn


Option vs. Accent
RR corn issues
 glyphosate timings
Field Corn
Option vs. Accent





POST grass control
except crabgrass
OP/SU interaction
roughly same cost/A
2004 Option was less
effective than Accent
Texas Panicum Control - I
Accent vs Option - 2004
Accent
Option
100
Control - %
80
60
70
a
70
a
90
84
abc
bcd
71
b
49
c
40
48
c
30
d
20
0
9 DAT
CN-03-04 (Ponder Farm)
Applied 22 DAP
PANTE = 1”, 3-4 leaf
28 DAT
54 DAT
Time
104 DAT
Texas Panicum Control - II
Accent vs Option - 2004
Accent
Option
100
94
a
Control - %
80
79
60
ab
75
b
90
a
66
b
90
a
60
b
40
55
b
20
0
14 DAT
CN-04-04 (Attapulgus)
Applied 21 DAP
PANTE = 1-2”, 2-4 leaf
35 DAT
55 DAT
Time
104 DAT
Texas Panicum Control - III
Accent vs Option - 2004
Accent
Option
100
Control - %
80
60
73 76
ab ab
40
71
ab
68
a
61
abc
76
a
56
ab
55
bcd
55 DAT
104 DAT
20
0
13 DAT
CN-06-04 (Attapulgus)
Applied 21 DAP
PANTE = 1-2”, 3-4 leaf
35 DAT
Time
Texas Panicum Control (104 DAT) - II
Accent vs Option - 2004
Untreated
CN-04-04 (Attapulgus)
Applied 21 DAP
PANTE = 1-2”, 2-4 leaf
Accent @ 0.67 ozs/A
Agrioil @ 1% v/v
Option @ 1.5 ozs/A
MSO @ 1.25% v/v
AMS @ 3 lbs/A
Conventional or RR Systems?
Are the RR hybrids any good?
Pioneer 31G98
DK 67-60RR
300
250
245 234
Bu/A
200
a
150
a
226
a
239
237
a
a
100
50
0
79
76
b
b
Untreated
Accent +
Atrazine
Dual fb Accent
Weed Management System
CN-07-04
Roundup WM
(split 22 ozs/A)
Use Rates for Glyphosate in RR Corn
RR-Corn
RR-Corn 2
Normal Rate/A
0.75 ae
0.75 ae
Maximum Rate/A
0.75 ae
1.12 ae
Maximum Total
In-Crop
1.50 ae
2.25 ae
Up to V8 or 30”
Up to V8 or 30”
30-48” (drops)
Timing
Soybeans






Nutsedge control in
RR beans
RR cotton in RR
soybeans
Mn tank-mixes
Sequence
tropical spiderwort
glyphosate timings
Nutsedge Management in RR Soybeans

split applications of
glyphosate
 better on purple than
yellow

tank-mix with Classic
 controls yellow
suppresses purple

tank-mix with Pursuit
 better on purple than
yellow
 rotations/cost
Controlling RR Cotton in RR Soybeans

Canopy - PRE
 metribuzin + chlorimuron
 8 ozs/A

POST glyphosate tankmixes
 Resource (4 ozs/A)
 Reflex (12 ozs/A)
 Classic (0.33 ozs/A)

need PRE fb POST to be
most effective
Glyphosate/Manganese Tank-Mixes

research from VA has
shown that Mn will
reduce weed control
when tank-mixed with
glyphosate
 9 to 38% reductions
depending upon species

Mn not a problem with
Blazer, Classic, Pursuit,
or Basagran.
Sources: Bailey et al., 2002 (Weed Technology 16:792-799) and
Heckman et al., 1999 (Journal of Production Agriculture 12:445-448)
Sequence for Weed Control in RR
Soybeans



label in October 2004
mixture of glyphosate -K
+ Dual Magnum
2.5 -3.0 pts/A
 $/15-18/A
 0.70 ae + 0.94 ai (2.5 pts)
 0.84 ae + 1.13 ai (3.0 pts)


prior to 3rd trifoliate
tropical spiderwort?
Tropical Spiderwort Management in RR
Soybeans

Use Dual Magnum or
generic PRE in known
fields

tank-mix Pursuit or
Classic with glyphosate

Extreme 2.17SC @ 3
pts/A = glyphosate (0.75
lb ai/A) + Pursuit (0.063
lb ai/A)
To Prevent Yield Loss in RR Soybeans



control weeds by 4-5
weeks after planting
or
control weeds before
they reach 6-9” in
height
or
control weeds before
the V3 stage
Source: Purdue University Extension Weed Science Group, 2004
(4.7 million acres of RR soybeans planted)
Sunflowers




Spartan
PPI or PRE
4F @ 3-3.75 ozs/A
only soil applied
broadleaf herbicide
registered
University of
Georgia
Extension Weed
Science
(gaweed.com)