When A Fungi Really Isn’t A Fun Guy
MT. VERNON, ILL.
Throughout the Midwest,
farmers have been frantically
harvesting their
soybeans, sorghum, corn
and other grains in order to
beat winter to the punch.
2009 has been a bit of an
odd year in that much of the
crop was planted late and,
as a result, was harvested late as well. Because
of the late harvest, much of the crop
has endured many wet events in the field (especially
those grains that were damaged by
insects) and has often become infested with
various molds and fungi that can render the
grain virtually unusable due to mycotoxins.
Mycotoxins can be formed on grain in the
field, during transport and even in the grain
bin. Common fungi such as Aspergillus,
Penicillium, Fusarium and others can produce
one or more mycotoxins that can cause
death, chronic problems and even cancer due
to damage to mammalian kidneys and liver.
Aflatoxin is a mycotoxin produced by the
fungus Aspergillus flavus that is formally
regulated. Others such as deoxynivalenol
(DON), vomitoxin and zearalenone may or
may not be regulated depending on grain
type, who is buying and grain use.
How can farmers reduce their problems
from these naturally occurring detrimental
compounds? In the field, use of genetically
modified seed can offer protection from insect
damage and subsequent fungal growth. Additionally,
careful and close monitoring of the
crop and timely pesticide applications will
help limit grain damage.
Once the grain is in the grain truck, other
measures can be taken to limit losses. Take
care handling the grain. Don’t run augers so
that the grain is broken, such as slamming
it into a hard flat surface. Screening the
grain before it is placed into the grain bin can
also help.
Whole kernels are less likely to have fungal
damage, while the fines composed of broken
kernels and dust provide large amounts of
surface area where fungi can thrive.
Grain moisture and temperature are very
important for controlling mycotoxin-producing
fungi. Bringing grain temperature below
50 degrees Fahrenheit will help suppress
fungal growth and will keep kernel-damaging
insects in check as well. Grain moisture
below 15 percent will suppress virtually all
fungi; however, care should be exercised in
keeping moisture from getting too low.
Most grain will become very brittle when
moisture drops below 12 percent and will
break easily, making more fines. Additionally,
remember that moisture is also grain
weight. I don’t know any buyer that will adjust
scale weight upward due to moisture
content, only downward.
Carefully monitor the grain to discover any
“hot spots” where local moisture and fines
may be sufficient to support fungal growth.
The average moisture of the bin might be 15
percent, but in spots, moisture can easily exceed
20 percent.
As a practical matter, grain that has higher
levels of mycotoxins should not be stored for
extended periods since toxin levels can increase
over time, especially if moisture and
temperatures cannot be kept in check.
Don’t combine grain from other bins in an
attempt to lower mycotoxin concentrations.
Removal of fines will frequently bring concentrations
below acceptable limits.
Δ
Dr. Douglas B. Jones, Extension Specialist,
Integrated Pest Management, University of Illinois