Recently there
have been numerous reports of "moldy corn" across
Minnesota. The late harvest, high moisture corn, and
continuing wet conditions have contributed to this
problem. At least two main questions should be
considered. Are the problems at this point significant
ear and kernel rots that are damaging the kernels, or is
the problem primarily superficial growth of fungi on the
grain surfaces? Both types of fungal growth on corn can
cause greater problems with grain quality if the corn is
not harvested and dried properly. The current problems
with "moldy corn" are still not completely clear, but we
can make some general comments on what we have seen and
heard so far.
Although there may be ear and kernel
rots or superficial surface growth of fungi occurring,
the detailed reports coming in to date suggest the
primary problem now is superficial growth on the surface
of kernels. Surface growth of fungi may be an
opportunistic situation where various fungi simply are
taking advantage of a wet, nutrient-rich environment to
grow. Once the corn is harvested and dried, they may
stop growing. Or if corn is not dried sufficiently and
is damaged, they may continue to grow and reduce grain
quality. Depending on the type of fungus and the storage
environment, these fungi may or may not produce
mycotoxins. The more severe ear and kernel rots may
damage a few kernels or large parts of a corn ear, and
may be associated with the presence of mycotoxins.
Several types of ear and kernel rots
and fungal growth and can occur on corn in MN,
especially Fusarium ear rot, Gibberella ear rot, and
Aspergillis ear rot. Aspergillis ear rot is generally of
greatest concern on corn due to potential production of
aflatoxin, but the cool summer this year did not favor
it in most parts of Minnesota. Diplodia ear rot appears
to be very uncommon in Minnesota. Other types of common
fungi that may grow on corn include Penicillium and
Trichoderma, and these may often have a superficial
growth habit.
More information on ear and kernel rot
fungi and mycotoxins can be found at these web sites.
http://www.extension.umn.edu/cropenews/2007/07MNCN42.html
http://agcrops.osu.edu/corn/EARABNORMALITIES.php#Diplodia
http://www.uwex.edu/ces/crops/MoldsMycotoxins.pdf
Diagnosis and harvest can help
clarify the problem with "moldy corn" and reduce or
solve it. For diagnosis and identification of the
types of fungal growth and kernel infection on corn,
samples can be sent to the Plant Disease Clinic at
the University of Minnesota (http://pdc.umn.edu/).
Harvest and drying may be the solution. The problems
that we have been seeing most often may be stopped
or slowed by harvesting and drying the corn.
Information on harvesting and drying can be found in
this article (http://www.extension.umn.edu/cropenews/2004/04MNCN22.htm
) and this Minnesota late harvest web site (http://www.extension.umn.edu/lateharvest/).
