STRAIGHT FROM THE HORSES MOUTH

Duane A. Lienemann
Unl Extention Educator
 

                         

     Drought and its effects are often part of growing corn in Nebraska, especially in rain-fed fields. Although we can do little to influence the weather, we can make management decisions that minimize the impact of the drought on the utilization of the crop. Of course we expected to see stunted and some withered corn. We also expected to see no ears or for sure just nubbins on the corn stalks. Let’s take a look this week at what many dry-land farmers and center pivot irrigators are finding on pivot corners. What first comes to mind is how our yield may be affected, but maybe there is more.
     It is no secret that drought stressed conditions may affect corn plant health and result in corn growers observing smut and other fungal activity in their fields. What we are seeing is likely Common, Head, or Boil Smut which is caused by the fungus “Ustilago maydis” which attacks the leaves, stalk or ear. It is most noticeable as grayish black galls on the ear of the plant. The fungus is composed of numerous races that can differ in cultural behavior and pathogenicity. However, most galls seem to be a result of infection by primary inoculum that survived in the soil from the previous growing season. The incidence of common corn smut varies from year to year depending on environmental conditions. The smut contains little or no mycotoxins and believe it or not is considered an edible delicacy in some cultures. I believe that in Mexico it is called “Huitlacoche”, aka Mexican Truffle!  For some reason that does not appeal to me, but then I guess I have never tried it.
     When heavy infestations of corn smut occur, grain yields can be so severely decreased that the most viable economic alternative may be to harvest and ensile the crop. Smut is generally known as one of the dry season diseases. It also occurs from mechanical injury to plants such as machinery, hail, wind damage, herbicides and detasseling injury. Smut usually occurs where hail or hard driving rains occur in earlier stages of growth. Optimum growing temperatures are 80-93° F. The disease is more common when corn is grown in soils with high nitrogen levels, and particularly following manure applications. All corn is generally considered susceptible. Some pedigrees are more prone, but the disease is not prevalent enough to rate hybrids. Despite that knowledge that smut will indicate a much lower yield, it doesn’t bother me as much as some of the mold that I am finding in a lot of ears ….and yes, nubbins out in our dryland corn. Is there any concern?
    We expect smut and other diseases in corn stressed by drought or by other problems. But as the crop deteriorates, decaying molds can become a problem. While ear rots such as Trichoderma, Ustilago (smut), and Diplodia do not produce known toxins, the observations of these molds should serve as warning signs that a mycotoxin could be present from other non-visible molds also growing in the plant. Even those mold organisms that can produce toxins do not always do so depending upon the environment. Most mycotoxin producing funguses are of the Fusarium, Aspergillus, or Penicillium families and are not directly associated with visible foliar or grain fungus diseases. 
     Hot, dry conditions associated with drought years are generally not thought to be conducive to growth of typical Fusarium molds that are common in Nebraska, but if European corn borer damage to the ear is significant, Fusarium molds can develop. Fusarium molds often appear as white or pink molds on the ear and are responsible for most of the mycotoxins we encounter in Nebraska. Hot, dry conditions however are conducive for the development of Aspergillus fungi, which is sometimes reported in Nebraska. Some species of Aspergillus can result in aflatoxin. The Aspergillus fungus is a greenish yellow mold that appears on the ear. Now we have to worry if that will be a problem in grain, forage or silage.
      Usually the presence of the mold does not indicate that mycotoxins will be present. However, the only sure way to determine if mycotoxins are present is through testing if a problem is suspected. Testing corn for mycotoxins is a good idea if mycotoxin concerns exist. You may want to be aware of this if you plan to harvest this corn. If you do make silage out of this corn I suggest following recommended silage management practices and inoculation. Inoculants will produce good fermentation to minimize chances of continued mold activity and mycotoxin production in the silage pile.  
    If you need feed for livestock you might consider putting it up for silage, green chopping or rolling it up in bales. Any corn that has pollinated and stays alive will use any rain to fill grain and that will add to the value of the crop for feed. If you decide to bale it, technically you could lay corn in a swath and let it dry. There are some challenges. Even if run through a conditioner, it can take a long time for wet stalks to dry. Stalks in a swath can start to spoil before they are dry enough to bale. It can be difficult to pick up corn swaths that lay between corn rows without raking through a lot of soil.  
     Another option may be grazing. Grazing saves the cost of fuel and operating chopping equipment. Where possible, use an electric wire or other means to limit access and minimize waste. This may be more feasible with short corn. A more viable alternative may be putting it up for silage. I know that the thought of feeding smut infested corn silage may appear visibly unappealing, however there is no known mycotoxin associated with smut.  I did a little research and couldn’t find much on the effects of feeding cattle however there was a Texas study looked at feeding smut infested corn to sheep and they found no detrimental health effects to develop in the animals. The study showed no changes in digestibility and actually demonstrated that sheep had increased dry matter intakes over feeding of non-infested corn silage. Perhaps the entrepreneurs out there can convince consumers that they should try “Huitlacoche” ....Mexican Truffles anyone?

The preceding information comes from the research and personal observations of the writer which may or may not reflect the views of UNL or UNL Extension. For more further information on these or other topics contact D. A. Lienemann, UNL Extension Educator for Webster County in Red Cloud, (402) 746-3417 or email to: dlienemann2@unl.edu or go to the website at: http://www.webster.unl.edu/home