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Bob Scott
My name is Bob Scott. I am a Extension Weed Scientist with the University of Arkansas
Division of Agriculture Cooperative Extension Service. I'd like to talk to you today about
a little bit of the work that we are currently conducting at the Rice Research & Extension
Center here at Stuttgart, AR.
The trial that we are standing in right now is a long term rotational study. You are looking
at effects of continuous clearfield rice on red rice populations. Clearfield rice currently
make up to around 60-70 percent of the rice acres grown here in Arkansas.
We have a concern that the overuse or continued use of this technology since its introduction
in 2002 may be leading to the development of the resistance of the red rice populations.
The objective of this study is to evaluate a number of rotational strategies, everything
from continuous clearfield rice to using nothing but ALS technology, up to a couple of years
of fallow following a full infestation of red rice.
This study also includes rotations with liberty link & roundup ready soybeans.
To date we have determined that we do in fact see a buildup of red rice when we go continuous
clearfield rice. By simply delaying the planting date in continuous red rice system, we have
reduced red rice populations by as much as 60-70 percent.
We have also shown in this study that by rotating to roundup ready or liberty link soybeans
or by conducting one year of fallow, that is by laying a field out, & preventing any
red rice from germinating, that we have effectively reduced red rice population by up to 80-90
percent.
This is the second year of a three year study. Next year this entire area will be planted
back to clearfield rice so we can determine after three years of various rotation strategies
which ones are the most effective at reducing red rice populations, compared to continuous
clearfield production.
In order to initiate this study in year one, this entire field that I am standing in was
allowed to go to seed. It was completely grown up in red rice. It also had some volunteer
clearfield rice in it. So that's how we establish this area in a known red rice infested field.
The actual plot I'm standing in is plot #1. In year one this entire treatment was clearfield
rice with nothing but new path followed by new path. This year in year two of the rotational
study, we dug a levy down the center of the plot. As you can see we have rotated half
the plot to soybeans, the other half remains in a continuous clearfield system.
Further u pin this tier is an untreated check which gives us an idea of the red rice populations
that we continue to deal with in this field. As you can see our soybean treatment is providing
excellent control over red rice. We have detected a few red rice plants escaping in the continuous
clearfield rice system.
Another area of research we have here at the Rice Research & Extension Center here in Stuttgart,
AR is in the area of barnyard grass. Barnyard grass continues to be the #1 weed control
problem in rice. Since the introduction of clearfield rice in 2002, we have really had
no new chemistry to combat barnyard grass in rice production fields.
Command continues to be the foundation in both conventional & clearfield rice for the
control of barnyard grass. As a service to the growers here in Arkansas, Dr Jason Norswerthy,
my research counterpart in Fayetteville conducts annual surveys of barnyard grass resistance
in the state of Arkansas. These samples are sent in by county agents from all over the
state. We bring those samples here to Stuttgart to conduct research on both the control, biology
of these weeds.
The research conducted here for barnyard grass because we have no new chemistry, simply involves
taking a population of barnyard grass that say is resistant to propanil & then building
a weed control program around the control of this pest in the absence of propanil .
To date, we have detected propanil, facet, command & new path resistant barnyard grass,
which leaves us with only a few modes of action left to control of this weed should it ever
become that all populations are resistant to those families of chemistry. The research
conducted here in Stuttgart at the Rice Research & Extension Center will help provide growers
in the future with ways to control this #1 pest in rice.
Another area of research we are conducting here at the Rice Research & Extension Center
is looking at pigweed control on rice levees. Glyphosate resistant palmer amaranth, or palmer
pigweed has become a major problem throughout the state. Rice rotation is a good cultural
practice for control of this pest & other crops such as corn, cotton & soybeans. However,
in certain counties in Arkansas the application of 2-4D has been restricted after April 15th.
2-4D is the most effective pigweed treatment that we currently have in rice, but for those
areas that are too close to cotton or other sensitive crops, or that are in the restrictive
counties, they don't have the 2-4D option to use on levees. In this particular study
we're evaluating various other treatments for the control of pigweed & other broadleaf
weeds on rice levees in Arkansas.
Let's go over now & take a look at one of our more effective program approaches for
pigweed & broadleaf control on levees.
In those areas where 2-4D is not an option, a planned program approach for palmer amaranth
is a much better option than trying to wait & go post emerge. Late post applications of
products like aim & propanil or grand stand in propanil are effective in controlling smaller
2-4 inch palmer amaranth. Anything that gets any bigger than that is where we used to rely
on 2-4D for control which we no longer have in some cases.
The plot that I'm standing in front of here received a preflood application of prow & facet,
followed by an early post of levee application of grand stand & permit. And this planned
approach applied to this levee has provided effective pigweed & broadleaf weed control
as you can see.
Since the introduction of herbicide tolerant crops, mis-application & herbicide drift have
been a common problem throughout the state. The University of Arkansas is sponsoring a
program called flag the technology that will hopefully alleviate some of the problems with
identifying fields according to the herbicides in which will tolerate them. Flag the technology
was initiated this year in 2011 & we have seen rapid adoption. The flag colors are red
for conventional, white for roundup ready, green for liberty link & yellow for the clearfield
technology. By placing a flag with the appropriate color in the corner of a field, the grower
can identify that field according to its herbicide technology.
Our hope at the University is that this will help prevent the mis-application of herbicides
or the drift of herbicides onto these fields thereby improving crop production.