Corn and Soybean Herbicide Update
Chris
Boerboom
There are few new herbicides to review this year in the corn
and soybean market compared to previous years. For some of the
more recently labeled herbicides, you may wish to review summary
comments made in the previous issues of the Wisconsin Crop
Manager: Define, Harmony GT, Steadfast, Amplify, and Gauntlet
were summarized in February 2001; Valor was summarized on April
26, 2001; and Callisto was summarized on June 7, 2001.
Phoenix is a new formulation of lactofen, which is the
same active ingredient as in Cobra. Phoenix contains 2 lb/gal of
lactofen plus an adjuvant system. Use rates are 8 to 12.5 fluid
oz/a plus 0.125 to 0.25% of nonionic surfactant. At the high
rate, 3 inch eastern black nightshade, 4 inch pigweed, 6 inch
common ragweed, 4 inch giant ragweed, and 6 inch waterhemp are
labeled for control. When larger or additional broadleaf weeds
are targeted, 1 pt/a crop oil concentrate is recommended as the
adjuvant. Phoenix will still cause bronzing or speckling of
soybean leaves, but the degree may be less than with Cobra. When
crop oil concentrate is used as the adjuvant, injury will
increase and may be similar to Cobra. Phoenix can be tank mixed
with numerous postemergence herbicides such as FirstRate,
Raptor, Pursuit, glyphosate, and Select. Applications need 2
hours to be rainfast, which is longer than with Cobra (30
minutes).
The Callisto label has one major change this year,
which affects rotational restrictions. Small grains can still be
planted 120 days after application and soybeans, sorghum,
potatoes, sunflowers, tobacco, and sweet corn can be planted the
season following an application. However, the interval has been
extended to 18 months for the following crops: beets, peas, dry
and snap beans, cucurbits, red clover, alfalfa, and non-listed
rotational crops. The extended rotational restrictions for these
crops is because of concern for carryover injury.
Several other new supplemental labels are related to Callisto.
DuPont has 2(ee) labels for full rates of Accent Gold or Basis
Gold to be tank mixed with Callisto at 1 to 3 oz/a to enhance
broadleaf weed control. A Steadfast 2(ee) label also recommends
a full rate of Steadfast to be tank mixed with Callisto at 1.5
to 3 oz/a. The label recommends adding atrazine to this tank mix
to control larger broadleaf weeds and common ragweed. Dow also
has a 2ee supplemental label that allows 3 oz/a Hornet WDG to be
tank mixed with 1.5 to 3 oz/a of Callisto and applied
postemergence. The addition of the reduced rate of Callisto will
improve control of lambsquarters, pigweed, and waterhemp over
Hornet alone according to the label. I would also expect greater
eastern black nightshade control with the addition of Callisto.
These supplemental labels conflict with Syngenta’s
recommendation on the Callisto label that applying less than 3
oz/a of Callisto may result in reduced weed control. Obviously,
marketing drives some of these label positions. [A 2(ee)
supplemental label is a recommendation that is permitted under
FIFRA such as a tank mixture of two labeled herbicides. 2(ee)
labels do not need EPA approval.]
Lorsban 15G also has a supplemental label allowing T-banded
applications of Lorsban to be followed by postemergence
applications of Callisto. The Callisto label warns that such
applications may result in severe corn injury. The actual risk
of this injury may be low, but if it were to happen, Dow would
be responsible because their Lorsban label made the
recommendation for this use.
Accent Gold WDG has been labeled. It is a new formulation
of Accent Gold that contains Hornet WDG, which replaced the
original Hornet. Accent Gold WDG has a use rate of 3.5 oz/a and
provides the same herbicide rate as the original Accent Gold,
which was used at 2.9 oz/a. As Accent Gold stocks are used and
replaced with Accent Gold WDG, be sure to adjust to the new rate
or you will be applying less herbicide than planned.
Aim has been marketed as a 40% dry formulation in
previous years and had a use rate of 0.33 oz/a. Two new liquid
formulations of Aim (Aim EW and Aim EC) are now labeled for the
same uses on field, seed, and sweet corn. The new Aim EW
formulation contains 1.9 lb/gal of carfentrazone and Aim EC
contains 2 lb/gal. Both are labeled for use at 0.5 fluid oz/a,
which provides essentially the same rate of carfentrazone as
0.33 oz/a of the dry formulation.
Option is the only herbicide with a new active ingredient
(foransulfuron) that is expected to be labeled this year. Option
is a postemergence ALS-inhibiting herbicide that controls
grasses and several broadleaf weeds in corn. It will be
summarized when it is officially labeled.
Remember that this is the final year that Bladex and Extrazine
II can be used in field, seed, or sweet corn. Cyanazine, the
active ingredient in Bladex and a component of Extrazine II, is
in the process of being phased out and will not be registered
for use after 2002. Therefore, make sure that you use all
remaining stocks this spring. The maximum use rate for
applications this year is 1.1 lb/a Bladex 90DF, 1 qt/a Bladex
4L, 1.5 lb/a Extrazine II 90 DF, or 1.3 qt/a Extrazine II 4L.
March, 2002 |
