Lodged Corn May Mean Problems In Wheat
PRINCETON, KY.
A significant amount of
corn lodged as a result of
the strong winds associated
with Hurricane Ike. This
lodging increases the risk that
volunteer corn plants will
eventually appear either this
fall or next spring.
There is some debate
whether volunteer corn is a threat to wheat.
One viewpoint is that volunteer plants that
emerge in the fall
will eventually be
killed from fall’s
freezing temperatures
before they
can impact wheat.
Another opinion is
that early-season
competition from
volunteer corn will
impact growth and
yield of wheat.
Limited research
this past season
showed 11 percent
lower wheat yield if
volunteer corn was
not controlled in the
fall prior to wheat
planting. It is not
clear if this trend in
yield loss will hold
true for every case,
but it does show significant
economic
losses can occur
from volunteer corn
competition.
The germination pattern of volunteer corn
may be uniform or sporadic depending on a
number of factors including duration and pattern
of rainfall following harvest. Volunteer corn
at UKREC germinated uniformly last season
due to the rainfall over a six-day period soon
after corn harvest and a three-day period approximately
two weeks later. The development
of volunteer corn was fairly uniform and ranged
from 6 to 8½ inches tall at the time of planting
wheat in mid October. Sporadic germination
patterns that are associated with irregular rainfall
may make it difficult to determine the optimum
time for controlling volunteer corn. It is
possible that implementing control options well
ahead of wheat planting will allow for escapes if
seed germination is extended over a long period.
Options for managing volunteer corn include
preplant tillage or foliar-applied herbicides.
Tillage provides immediate results, but may increase
the risk of soil erosion and more time relative
to using burndown herbicides. While
tillage will destroy emerged volunteer corn
plants, it may stimulate germination of any remaining
seeds that were incorporated in the soil
during the tillage process.
Glyphosate controls volunteer corn providing
plants do not originate from corn with the
‘glyphosate-tolerant’ or Roundup Ready trait.
The fact a significant number of corn acres in
this region are planted to glyphosate-tolerant
hybrids limits the opportunity to use
glyphosate. Glyphosate usually requires 7 or
more days to kill plants; consequently, it may
not be the right choice if immediate control is
needed.
Paraquat provides rapid control of vegetation;
therefore, it may be preferred over glyphosate if
speed of control is desired. Paraquat helps manage
volunteers with GMO traits, including
glyphosate-tolerant corn. Paraquat alone tends
to be inconsistent in controlling corn that originates
from seed that were planted or incorporated
in soil. We have seen this when we try to
kill corn for replant situations in the spring.
However, limited research last fall showed at
least 95 percent control for corn plants from
seeds that were not incorporated into soil. Our
current theory is that the growing points of volunteer
corn plants originated from seed on or
near the soil surface and were exposed to
paraquat and other related stresses.
Finesse was evaluated last fall as an option for
controlling volunteer corn. Volunteer corn is
NOT listed on the Finesse label. Test results
showed that Finesse provided up to 60 percent
control of volunteer corn within 7 days after
planting no-till wheat. Frost occurred before
Finesse reached maximum activity; consequently
we were unable to determine if the herbicide
would have eventually killed the
volunteer plants. Finesse is a premix of ALS inhibitor
herbicides and is slow in its activity. The
fact that Finesse has soil-residual activity
is a potential advantage for controlling later
emerging volunteer corn plants as well as Italian
ryegrass. The label requires a minimum 6-
month interval between application and
planting STS soybeans. Δ
Dr. Jim Martin is Extension Weed Scientist
with the University of Kentucky at Princeton.