Harvesting Corn for Silage Infested with Corn Smut
Drought stressed conditions may affect corn plant health and result in corn growers observing smut and other fungal activity in their fields. Feeding smut infested corn silage may appear visibly unappealing, however there is no known mycotoxin associated with smut. A Texas study looked at feeding smut infested corn to sheep and 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. Review "Influence of Corn Smut on the Palatability and Digestibility of Corn Silage" for a detailed summary of this study.
Common, Head, or Boil Smut is caused by the fungus Ustilago maydis , which attacks the leaves, stalk or ear. The latter is the most common as illustrated in the picture at the right. All corn is generally considered susceptible. Some pedigrees are more prone, but the disease is not prevalent enough to rate hybrids.
Smut is generally known as one of the dry season diseases. It also occurs from mechanical injury to plants such as machinery, hail, blowing sand, 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, particularly following manure applications. Maintaining well-balanced soil fertility is a major control measure.
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. Testing corn for mycotoxins is a good idea if mycotoxin concerns exist. Following recommended silage management practices and inoculation with Pioneer® brand 11CFT, 11C33, or 1174 inoculants will produce good fermentation to minimize chances of continued mold activity and mycotoxin production in the silo.