Corn Maturity Cutoffs For Herbicides
JACKSON, TENN.
April 16, 2012 – An early, warm and dry
spring has allowed for the planting of most
of our corn acres in Tennessee. This
weather that allowed for the early planting
should really increase the probability of good
corn yields this fall. However, this weather has
also caused some problems from a weed control
perspective as some of the pre-applied herbicides
did not receive an activating rainfall. As a
result, some fields have emerged weeds with the
corn. In other cases, the pre-applied herbicides
were activated with some timely precipitation
and have provided 20 to 30 days of residual
weed control. They will likely begin to play out
this week. Therefore corn fields in Tennessee
that are off to a good start have either emerged
weeds present or will likely see a new flush of
pigweed and grasses very soon.
Quite a bit of the corn I have seen ranges from
newly emerged to the V3 stage ( 3 leaf collars
open). It will not be long before corn that is in
the V3 stage will become too large to treat with
some herbicides. Several herbicides offer effective
postemergence weed control options, but
there are cutoffs associated with all of these.
This serves as a reminder for cutoffs timings for
several postemergence corn herbicides. Crop
stage and/or crop height can be used to determine
this and typically the label states the limits
so that whichever comes first is the cutoff.
Crop stage can easily be done by counting the
number of collars that are fully open (ex. 3 open
collars = 3 leaf), but crop height can also be
used. Refer to the 2012 Weed Control Manual
https://utextension.tennessee.edu/publications/
Documents/PB1580-2012.pdf for further
information and as always, read the herbicide
label!
One other thing to note is a newer product,
Realm Q. This is a combination of rimsulfuron
(Matrix) and mesotrione (Callisto). This product
provides postemergence control of broadleaf and
grass weeds, as well as residual control. The Q
stands for a built-in safener, allowing for safe
postemergence applications in corn.
Another reminder, but Ignite has now been renamed
to Liberty. This is still the same herbicide
and same formulation, just a new name. Liberty
can only be used on corn varieties with Liberty
Link tolerance just like glyphosate products can
only be used on corn varieties with Roundup
Ready tolerance. Δ
KELLY BARNETT: Graduate Research Assistant,
University of Tennessee
3 leaf (collar) corn - V3 stage