Recently many calls and questions have been raised regarding the increased observation of molds on corn that remains unharvested.

Producers across PA are looking for answers to questions related to identification and the potential for feeding challenges. Moldy grains are a complicated issue for grain producers and feeders and understanding these challenges requires information on mold identification and an understanding of mycotoxins risks and potentials.

Frequently moldy ears are associated with cool and wet environmental conditions during ear development and grain maturity. However other factors, more common this year, seem to have also resulted in moldy ears. One factor is when the corn plant stops growing late in the season during droughty conditions. When this happens the moisture in the cob and the grain are not removed by the natural dry down process but instead depend on air movement to dry down the ear. Under circumstances like this, the environment inside the husks provides ideal conditions for mold growth. Poor pollination can also favor mold development as poorly pollinated ears tend to remain upright on the stalk leading to exposure to mold spores and rainfall. European corn borer levels were high in many areas this summer due to the droughty conditions. Borers feed on the tips of the developing ears leading to exposure to mold spores. Last but not least, birds feeding on these caterpillars or other insects on the ear tips can cause damage leading to mold infection.

The three most common ear molds are Diplodia, Fusarium, and Gibberella. Diploidia is a whitish mold that first appears at the base of the ear. Try to associate “D” for Diploidia with “D” for Down. Eventually the whitish mold can cover the entire ear. Frequently blackish specks, actually mold fruiting bodies called picnidia can be seen on the outside of the husks. Diploidia will cause reduced feed value but this mold produces no known toxic affects.

Fusarium ear rot is noted for the fact that the disease is typically found “scattered” around the ear. It infects damaged kernals first. It is a whitish to salmon color. Fusarium is one of the most common ear rots found and can produce a toxin – fumonisin that can be a concern for feeding to horses. “Generally”, ruminants are not seriously affected by this mycotoxin.

The third ear rot is Gibberella. This is a whitish to slightly pink mold that starts its development on the tips of the ears. Interesting note is that this mold also causes head scab on wheat and stalk, seedling and root rots in corn. The spores of this disease can enter the ear through the silks during pollination. Gibberella ear rots can produce several mycotoxins harmful to livestock: vomitoxin (or DON) and zearalenone. Hogs are especially sensitive to these toxins but cattle and other livestock can also be affected.

Molds can be reduced in storage by two factors, temperature and moisture. At moistures less than 13% and temperatures below 40 degrees F mold growth and further grain quality losses will cease. Combining moldy ears, as soon as possible, is preferred over picking as many moldy and damaged kernals will be removed during combining. Grain cleaning prior to drying and storage will also remove many smaller kernals.

Ears for cribbing should be stored when grain moistures fall below 20%. Air movement in many cribs can be less than ideal. Often times, equipment or newer buildings have been placed that can restrict natural air movement needed to dry down ears. The removal of any fines, husks, etc. prior to cribbing is important for air movement within the crib. As with shelled corn, moisture levels less than 13% need to be reached to stop mold growth.

Molds do not always produce mycotoxins and this fact creates management complications. Some work has discovered that molds tend to produce more mycotoxins in response to environmental stresses including cool, moist conditions and/or drought. The mycotoxin from one ear rot may not cause health problems alone but other mycotoxins found in a silage feed or cottonseed or other feed ingredient may create problems. Testing of individual feed ingredients for mycotoxins can be done but we should include a complete mycotoxin screening of the ration if you suspect problems exist. Work with your veterinarian and your nutritionist to address potential problems early.

SOURCE: Paul H. Craig, Dauphin County Extension

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