New Herbicides
for Corn and Soybeans 2000
Chris
Boerboom
As new herbicides are registered
for use in corn and soybeans, I will provide brief summaries
with key points from their labels. In this issue of the
newsletter, I will highlight five new herbicide labels. Keep in
mind that there are no new active ingredients being registered
this year. All of the new herbicide labels are either new
premixes of existing herbicides, new formulations, or generic
versions of previous herbicides.
Axiom AT
Axiom AT is a 75% dry flowable
premix of Axiom plus atrazine for corn from Bayer. Recall that
Axiom is premix of flufenacet, an acetamide herbicide, plus
metribuzin. This means that Axiom AT is a actually a three-way
mix with 19.6% flufenacet, 4.9% metribuzin, and 50.5% atrazine.
This mixture will control many common annual grasses like
foxtails, crabgrass, and fall panicum.and many broadleaf weeds.
Expect some velvetleaf and giant ragweed to escape control as
with other acetamide plus atrazine premixed herbicides.
Axiom AT is labeled for field
corn, but not seed corn or sweet corn. The atrazine load in
Axiom AT does not match very well with Wisconsin’s atrazine
rate limits. Although Axiom AT is labeled for early preplant
applications up to 45 days before planting, the recommended
rates would often provide too much atrazine for Wisconsin’s
rate limits. Even with preplant incorporated and preemergence
applications (where rates are slightly lower than with early
preplant), only the lowest recommended rate can be used on
coarse soils to stay within our limits. The 2 to 3 lb/a range on
medium textured soils would give 1 to 1.5 lb ai/a of atrazine,
which fits our atrazine rates. Axiom AT is not to be used on
coarse textured soils with less than 1% organic matter or on
peat or muck soils.
Axiom AT can be tank mixed with
2,4-D, Gramoxone Extra, or glyphosate for burndown activity.
Other tank mixtures on the label that are reasonable are Banvel/Clarity,
Bladex, Hornet, Python, and Princep. Since Axiom AT contains
atrazine, only corn, sorghum, and soybeans should be planted the
ear after application.
Celebrity Plus
Celebrity Plus is a 70% DF premix
of Accent plus Distinct for corn from BASF. Recall that Distinct
is a premix of dicamba plus diflufenzopyr. This means that
Celebrity Plus is a three-way mix with 10.6% nicosulfuron, 42.4%
dicamba, and 17% diflufenzopyr. This mixture will control many
common annual grasses like foxtails, woolly cupgrass, and wild
proso millet. It will also control quackgrass, but it will not
control crabgrass. It will control many common annual broadleaf
weeds and suppress several perennial broadleaves.
Celebrity Plus is labeled for
field corn, including high lysine, waxy and white types, but not
seed or sweet corn. The use rate is 4.7 oz/a, which provides 2/3
oz/a Accent and 4 oz/a Distinct. Non-ionic surfactant at 0.25 to
0.5% and 1 to 2 qt/a 28% (or 1 to 2 lb/a ammonium sulfate) must
be included in the spray mixture. The label states that corn can
be sprayed from 4 to 24 inches tall, but I would not make a
broadcast, over-the-top application to corn past the V6 stage
because of the risk of pinched ears. Corn often reaches the V6
stage before it is 20 inches tall. Tank mix options include
Accent, Distinct, or atrazine. Celebrity Plus needs 4 hours to
be rainfast.
There are a few other key
precautions with Celebrity Plus. It can interact with
organophosphate insecticides and cause injury to conventional
corn hybrids (all hybrids except IR hybrids). Applications after
Dyfonate, Lorsban, and Thimet may cause temporary injury. Do not
use if Counter was applied in furrow; injury may result after
T-banded Counter. Celebrity Plus does contain dicamba, the
ingredient in Banvel, so care should be taken to avoid spray
drift and to carefully clean out spray tanks after use.
Rotational crop intervals are 1 week for field corn, 4 months
for soybeans and winter wheat, 8 months for spring cereals, and
10 months for sweet corn, peas, dry and snap beans, and alfalfa.
Boundary
Boundary is a premix with 6.3
lb/gal s-metolachlor plus 1.5 lb/gal metribuzin for soybeans
from Novartis. Boundary can be applied preplant surface,
preplant incorporated, or preemergence to soybeans. Two basic
programs are outlined on the label. One is to use low rates at
1.25 to 1.5 pt/a to give early season control of annual grass
and broadleaf weeds. The 1.5 pt/a rate of Boundary provides the
equivalent of 1.24 pt/a Dual II Magnum and 6 oz/a Sencor 75DF.
Then, escaping weeds would be controlled with a planned
postemergence herbicide application. The other program is to use
Boundary as one pass soil-applied herbicide at higher rates. On
coarse soils, 1 to 1.5 pt/a is recommended and 1.5 to 2 pt/a is
recommended on medium textured soils. To enhance control of
certain weeds, Boundary can be tank mixed with Python, FirstRate,
Command, or Prowl. In no-till, it can be mixed with 2,4-D,
Gramoxone Extra, or glyphosate for burndown.
Precautions on the label state
that soybeans should be planted at least 1.5 inches deep and
that injury (from the metribuzin/Sencor) may occur on soils with
less than 0.5% organic matter or if heavy rains occur soon after
application. Rotational crop intervals are 4.5 months for
alfalfa and winter wheat, 8 months for corn, peas, potatoes, and
spring wheat, 12 months for other crops, except roots crops
which is 18 months.
Domain
Domain is a 60% DF premix of 24%
flufenacet and 36% metribuzin for soybeans from Bayer. These are
the same ingredients as in Axiom, but the amount of grass
herbicide (flufenacet) is less and the amount of metribuzin is
more than in Axiom. Domain can be applied preplant surface,
preplant incorporated, or preemergence at 9 to 16 oz/a. The 16
oz/a rate gives about 40% of a standard grass herbicide rate on
a medium soil and the equivalent of about 8 oz/a Sencor 75DF.
This rate should provide early season control or suppression of
most annual grass and broadleaf weeds. Early season control is
described as 3 to 6 weeks of control. After that time, escaping
weeds may need to be treated with a postemergence herbicide.
Precautions on the label state
that soybeans should be planted at least 1.5 inches deep and
than injury (from the metribuzin/Sencor) may occur on soils with
less than 0.5% organic matter or if heavy rains occur soon after
application. Domain should not be used on sands with less than
1% organic matter or on peat or muck soils. The rotational crop
intervals for Domain are the same as with Axiom; 1 month for
corn and potatoes, 4 months for carrots, and 12 months for
alfalfa, barley, clover, and wheat. Vegetable crops are not
listed as rotational crops at 12 months.
Extreme
Extreme is a premix with 0.17
lb/gal imazethapyr (ingredient in Pursuit) and 1.5 lb ai/gal
glyphosate (ingredient in Roundup) by American Cyanamid. This
premix is labeled for Roundup Ready soybeans and will control
most annual grass and broadleaf weeds, but the glyphosate rate
may be a bit low to give long-term control of the tougher
perennials. The use rate is 3 pt/a as a burndown before no-till
soybeans (any type) or postemergence in Roundup Ready soybeans.
This rate provides the equivalent of 1.44 oz/a Pursuit DG and
1.5 pt/a Roundup. Extreme requires the addition of 0.125%
non-ionic surfactant and 2.5 lb/a ammonium sulfate (or 1 to 2
qt/a 28%). It should be rainfast in 1 hour.
A potential benefit with Extreme versus glyphosate alone is
that it will provide residual control of several weed species.
This residual activity may be a benefit in row soybeans or when
very early postemergence applications are made in drilled
soybeans. In these situations, weeds emerging after an
application of glyphosate may not be shaded out by the soybean
canopy, but the residual of Pursuit could provide the control.
We have not seen a benefit of tank mixing Pursuit with
glyphosate in drilled soybeans when applied at standard
postemergence timings (eg. V2-3). Extreme should be applied
before soybeans begin to bloom and generally before weeds exceed
8 inches. Because Extreme contains imazethapyr, it has the same
potential for stunting as with Pursuit. The rotational crop
intervals with Extreme are the same as with Pursuit.
January, 2000 |
