Corn Damaged by Common Corn Smut Under Stressful Conditions

BROOKINGS, S.D. -- Under the stressful conditions in 2002, corn has been infected by a common corn pathogen that causes common corn smut, a South Dakota State University specialist said.

SDSU Extension Plant Pathologist Marty Draper said the corn smut fungus will grow in any actively growing tissue of the corn plant, including leaf midribs, stalk nodes, tassels, and especially ears.

On the ears, the smut galls can grow to several inches in diameter.  The galls begin as small growths with a silvery membrane covering.  As they expand and reach maturity, the membrane ruptures, releasing many small, dark, dust-like spores of the fungus.

The fungus spore will survive in the soil, crop residue, silage, and manure for many years.  Under conditions favorable for disease, the spores will lead to
infection of a corn crop planted in the same field in successive years.  Conditions that favor infection include drought, hail, and low fertility.

"Corn smut is not toxic for livestock," Draper said. The fungus that causes corn smut has not been shown to produce mycotoxins that are harmful to the livestock or end consumer.  In fact, in certain Central American and South American cultures, the "corn mushroom", locally called huitlacoche in Spanish, is considered a delicacy to the native human population.

Livestock have been observed sneezing when eating smutty corn grain or corn stalks.  This is due to the structure of the smut spore.  It is very spiny on the surface and can be irritating to the nasal passages and may possibly be an allergen.

Conditions that favor common corn smut may also favor ear molds such as those caused by Aspergillus and Fusarium fungi.  Corn smut may be an indicator for producers to be sure to test feed grains for mycotoxins.  Aflatoxin, fumonosin, nivalenol, and deoxynivalenol (vomitoxin) are all produced in stressed corn that has been infected by ear rot and storage mold fungi.

More information on aflatoxin, can be found in "Aflatoxins: Hazards in Grain/Aflatoxicosis and Livestock" (FS 907).  This Extension bulletin is available from any county Extension office or on the internet at http://agbiopubs.sdstate.edu/articles/FS907.pdf.
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Contact: Marty Draper, (605) 688-5157
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Wendy Mohrhauser, Intern
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-5795