Hey, this is Tom Barber.
Extension Weed Scientist with the
University of Arkansas System Division of Agriculture.
I'm down at Tillar, Arkansas today evaluating some
of our corn herbicide trials.
And we really appreciate the support from the
Corn Promotion Board program that allows us to
evaluate these different system trials,
to see pretty much see what the best bang for the buck
is from a weed control standpoint.
Now, most growers in the state want to get the weed
control done in one application, and that's very difficult.
So, what we've done in this particular set of experiments
is we've looked at one shot programs and how they
compare either all up front or all early post.
One of the things that we wanted to look at in these
weed control plots is our grass control because
our counterparts across the river in Tennessee
have identified glyphosate-resistant barnyardgrass.
So, it's important to know what that might mean for our
corn producers moving forward were
we to get into that situation.
So, as usual, we have our untreated checks randomly
throughout the experiment.
The majority of the weeds in this test is either gonna
be pigweed or a grass species.
We've got three different grass species out here.
We've got broadleaf signalgrass, we've got
barnyardgrass, and we've got a little
southwestern cupgrass.
And so, we're looking at these systems either pre and
post to determine which one is the best system
if we're gonna try to get by with one application.
And because we're treating it like we have some
glyphosate-resistance in our grass population,
we're not using any Roundup in this experiment.
So, we just want to compare the mixtures and how
well they do without Roundup.
And so, again, I looked at several different herbicide
combinations all at once, up front or all post.
And the first plot, I want to show you kind of sets a
baseline, because our general recommendation in corn
production in Arkansas is always go
out with something up front.
And a lot of times that's S-metolachlor
or Dual II Magnum.
And so, obviously, this corn is fairly old.
I believe it's been six weeks since we've planted this
corn and sprayed the Dual Magnum
pre at a pint and a third.
But you can see it's pretty much lost all of it's control.
We've got pigweed, we've got grasses,
we've got everything that we have in our untreated
checks is coming out in this plot,
including some morningglory.
And so if we're talking about a one-shot program,
Dual II Magnum is not going to carry
us through the season.
We need multiple products.
And so, if we turn our attention to the next plot,
we'll see what that looks at,
and we'll look at multiple different mixtures of
herbicides to compare to just Dual by itself.
We just looked at Dual Magnum applied at
planting and that's all that that last plot had,
and we saw how that herbicide has broke.
And we have a lot of weeds germinating and emerging
in that system with just Dual.
The next thing I want to show you
is Corvus plus Atrazine plus Warrant.
And so, when we mix three products like that together,
we're gonna get more of a broad spectrum control.
And this is one of the typical Bayer programs that they
promote in the state for corn production.
So this is one application at planting of Corvus, Warrant,
and 2 quarts of Atrazine, and it is a fairly clean plot.
We have some grass coming up.
In general, when I rate Corvus plots,
the grass is the first to break.
Warrant is probably not as strong
a grasser as Dual II Magnum.
But most of these species we have in here is nutgrass.
And so none of those work on that very good.
We've got some barnyardgrass coming up right there.
And some broadleaf signal grass on the edges.
And so it's starting to break.
It's not near as big of species or near as big a weeds in
this plot as it was the Dual by itself.
So we've got a broader spectrum of control.
But we're still not going to carry all season just putting it
out pre-emerge, not even with those three products.
We're talking about single applications,
pre only applications.
And the next one we're going to look at is
Verdict and Atrazine.
So, this is 2 quarts of Atrazine and 10 ounces of Verdict.
And really, the only thing left in these plots, and again,
these are six weeks old,
is the grass that you start to see coming up.
And so, a fairly clean plot, but we've got some escapes.
Looks like broadleaf signalgrass
and a little bit of barnyard grass.
The only thing we did in this plot at planting was add
Zidua to the Verdict and Atrazine.
And what it's done is it's extended some of that residual
control of some of the grasses that we had escaped
in the last plot.
So, 10 ounces of Verdict, 2 quarts of Atrazine,
and 4 ounces of liquid Zidua or Zidua SC.
And we've still got a pretty clean plot
6 weeks after application.
The next one we're gonna look at is a
very simple program.
It's a pint and a third of Dual II Magnum
plus 2 quarts of Atrazine.
It's economical.
It provides decent weed control,
but at 6 weeks you can tell we've got some escapes,
not near as clean as the plots we've been looking at
with three herbicide modes of action up front.
Alright, as we stated at the beginning of looking at
these different plots, we're looking at one-shot
programs, and we really were focusing on grass control.
Obviously, we're going to look at the broadleaf control
that we have, but in a situation where a Roundup may
not work anymore, especially on some of our grasses
like barnyardgrass.
So, this particular plot is Steadfast plus Atrazine
and a couple of things you'll note.
So this is 2 quarts of Atrazine plus an ounce and a half
of Steadfast Q.
And one thing you'll see right off the bat is we've got
some injury on this corn.
And a lot of that injury we're attributing to the fact that
the corn may have been a little too big because of the
rains and how they fell this year.
We didn't get our applications timely and that happens
to a lot of producers, that's real world.
But where we see the mixture in Steadfast Q,
we're seeing more injury than we're seeing with some of
the Accent Q plots, I'll show here in a minute.
But for a general weed control standpoint,
it did much better than I could ever expect with just
Steadfast and 2 quarts of Atrazine.
Obviously, we had some pigweed up front there and
in the back that were too big.
But when we're talking about grass control,
excellent grass control activity out of the Steadfast Q.
Just always remember your growth stage restrictions
for Steadfast Q, and if you go a little over,
you can see some injury.
We also have some corn hybrids that are more sensitive
to ALS herbicides,
which Steadfast Q is an ALS herbicide
and you can see some similar injury to this
on those corn hybrids.
We're out here looking at total post programs
for grass and pigweed control.
Again, we're focused on grass a lot in this particular
project just in case we lose Roundup in some of our
grasses to a resistance.
And so we look at this particular plot,
this is this is Shieldex, which is a fairly new HPPD
herbicide that is registered in corn —
Shieldex plus 2 quarts of Atrazine.
Again, we've got excellent control of our broadleafs.
All this had was one application on it 3 weeks ago.
We got excellent control of our broadleafs but some of
our grasses have come back and we didn't get good
coverage maybe, but we've got because of all the weeds
present, but we've got a lot of barnyardgrass,
broadleaf signalgrass, and some
southwestern cupgrass in this plot.
We also have some nutsedge, but we didn't expect
much control with the yellow nutsedge
from that treatment.
But again, it just shows how important Roundup can be
in a total post system if we don't have
a good grasser in the mix with that.
The next total post we're going to look at is
Armezon PRO at 16 ounces plus 2 quarts of Atrazine.
And overall, I'm very pleased with the control in this plot,
especially compared to our untreated check next door.
We had excellent weed control overall, but again,
we're leaving some of these grasses and it just goes to
show the importance of having Roundup in that
post-emergence tank mix to take care of those grasses.
And so in the absence of Roundup,
we've looked at Steadfast Q earlier,
nothing is quite as effective on grasses as some of the
ALS herbicides such as Accent Q or Steadfast Q.
Next total post we're going to look at is Realm Q
plus 2 quarts of Atrazine.
And again, much like we saw in Armezon Pro,
this one didn't quite give us as good a grass control with
the Realm Q which has Callisto and Rimsulfuron in it.
Here in a minute, we'll look at Accent Q,
which seems to be a little better on some of the grass
species that we have here.
But again, what we're seeing is escape grasses from
that one post-emergence application,
Realm Q plus Atrazine.
The next total post we're going to look at is a
fairly new herbicide from Syngenta called Acuron XR.
It has 2 HPPDs,
one being Callisto, one being Bicyclopyrone,
and then it also has Dual II Magnum,
as well as a little bit of Atrazine in it.
And then we added more Atrazine.
So we have 96 ounces of Acuron XR plus 24 more
ounces of Atrazine, which gives us our 2 quarts.
And when we look down through here again for a total
post-program,
a very good control of grasses and broadleafs.
We have some vines here that are left,
honeyvine milkweed, and then maybe a little redvine
right there and some yellow nutsedge.
But you can see in some of this it's bleached out,
and that's said HPPD working right there
on some of that.
Pretty clean plot for a one-shot program,
Acuron XR plus Atrazine.
So one of the last over the top total post
programs we're going to look at today is
Accent Q and Atrazine.
Accent Q of .9 ounces and 2 quarts of Atrazine.
And when I look at this plot, what I have left,
I've got a lot of yellow nutsedge that we didn't expect to
get with that herbicide, either of those herbicides.
I also have a few grasses that are still here,
even though Accent Q has really good activity
on grasses, it's not near as clean as a plot where we had
Steadfast Q out for our grass material.
And so, although Accent Q and Atrazine look pretty
good here and we've probably rescued this crop from
any more yield loss due to weed control,
we still are gonna have a lot of weeds to deal with
throughout the season and by harvest and they'll seed
out and causes more problems next year.
So just to wrap up some key basics, corn weed control,
pigweed is a big issue for us, morningglories,
and then grasses,
and grasses can become much bigger of an issue if we
run into some glyphosate-resistant barnyardgrass like
they're seeing in Tennessee.
And so, what we recommend is always going out with
multiple residual herbicides.
Generally, we like going out up front with either Dual
or Verdict or something at planting to buy some time to
get a total post or not our total post,
but our post-application out,
which again expands our residual activity and gives us a
little longer length of residual altogether.
But from our pre programs, 3 products mixed together.
A lot of times we're still clean at 6 weeks.
Now, we'll see how that plays out
through the end of the season.
But, if you wait and do that to a total post,
a lot of times you're gonna have some misses
and it could be due to coverage,
could be due to size of the weeds and just the sheer
weed spectrum that's there by the time you get around
to your total post-application.
So again, in my opinion, putting it all out up front is
better than putting it all out post.
But overall, to minimize your pressure,
early season and late season,
the two-shot program is gonna be best for us and
our corn production system.