Dicamba ShortageWill Force Use Of Substitutes
JACKSON, TENN.
From visiting with retailers
the past month it is very
apparent there will be a
major shortage of dicamba for
burndown this spring. A number
of folks from different retailers
have stated that they
have been allocated only
about 20 to 25 percent of all
the dicamba they sold last year. The cause of
this shortfall apparently comes from some overseas
suppliers who decided for whatever reason
to shut down production. Apparently this problem
cuts-across companies as even Latigo, a
premix of dicamba and 2,4-D marketed by Helena,
will be in short supply.
Dicamba-based burndown programs have
been the backbone for horseweed (marestail)
control in Tennessee for over a decade. It now
looks like for many acres we will have to go with
a plan B. Other options for burndown of horseweed
are 2,4-D, Sharpen, Verdict, Gramoxone
and Liberty.
The herbicide 2,4-D can be about as effective
as dicamba on horseweed provided the rate is
high enough. When applied alone or with
glyphosate, I have never had consistent control
of horseweed with rates of 2,4-D less than 32
oz/A (1lb/A). Even with this rate if the horseweed
was well established from the previous
fall, control can be somewhat inconsistent.
Tankmixtures of 1 oz/A of Sharpen with a pint
of 2,4-D in soybean can be a more consistent
option for established horseweed. The plant
back to soybean from a 2,4-D application is 7
days at the 16 oz/A rate and 15 days for 32
oz/A. The plant back to cotton regardless of rate
is 30 days.
Sharpen and the premix of Sharpen and Outlook
(Verdict) can be effective horseweed burndown
options. Utilized in a tankmix with
glyphosate we have found horseweed control
with Verdict, which is a EC formulation, to be a
little more consistent across environments than
Sharpen which is a SC formulation. The three
way premix of glyphosate plus Sharpen with 1
pt of 2,4-D has been a very consistent control
option for horseweed.
Gramoxone (paraquat) can also be utilized as
an early pre plant burndown for horseweed.
However, in our research utilized alone in an
early burndown situation, it has proven to be
more inconsistent then the options listed above.
I really like it applied right behind the planter
to help finish off any horseweed that may be recovering
from the early burndown and to make
sure no Palmer amaranth is emerged before the
crop. Gramoxone control of horseweed and pigweed
can be improved if tankmixed with
metribuzin in soybeans and Cotoran or Caparol
before cotton.
Though Liberty can be an effective burndown
option for horseweed, I would not recommend it
for three reasons. First under cool spring conditions
Liberty will not provide good horseweed
control. Second, the options listed above would
be much more economical. Third, there is a
concern that if much Liberty is used for burndown
there may be a shortage of it for the more
needed in-crop applications this summer. Δ
DR. LARRY STECKEL: Extension Weed Specialist,
University of Tennessee