Dealing with Smut Contamination in Corn

Corn grown in wet conditions is at risk for contamination with smut. Yet, high-quality silage can still be made from affected crops.

 

Damage from Smut

Producers may see reduced corn yields due to smut contamination. Corn smut is caused by the growth of the fungus Ustilago maydis, which thrives in conditions of high humidity, poor pollination or damage from insects or equipment.

Once the plant is infected, the fungi’s cells divide quickly and expand. This leads to large gray galls that contain black spores, typically on the corn ear tip. The resulting galls decrease grain yield anywhere from 9% to 40%.1

 

Ensiling Challenges

The disease can restrict the rate and extent of fermentation as well as predispose the plant to further mold growth and the production of mycotoxins.

Using a forage inoculant can help address ensiling and feedout challenges. Producers should choose an inoculant that is research-proven to help drive a fast, efficient initial ensiling fermentation and inhibit the growth of detrimental spoilage microbes during feeding.

Specific bacteria strains and enzymes can help address these ensiling challenges. The lactic acid bacteria Pediococcus pentosaceus 12455 — fueled by sugars generated by high-activity enzymes — can help promote a fast, efficient front-end fermentation. To address challenges during feedout, an inoculant containing the high dose-rate Lactobacillus buchneri 40788 can help improve the aerobic stability of silage.

 

Feedout Effects

Ustilago maydis does not itself produce toxins, and studies in sheep have shown it does not affect feed intake.”2

When fed, Ustilago maydis can affect feed efficiency. Feed digestibility also can be reduced when infestation levels reach 50% or greater.3 Research shows total digestible nutrients (TDN), net energy for maintenance (NEM) and net energy for gain (NEG) values of corn silage decreased around 0.5%, 0.02 mcal/g, and 0.02 mcal/g, respectively, for each 10% rise in smut-infested plants.2

Corn contaminated with smut also is likely to be more variable than normal. Producers should have silage samples analyzed regularly — at least once a month — so adjustments to the ration can be made as necessary.

 

1 Ullstrup AJ. Diseases of Corn. In: Corn and Corn Improvement. Sprague GF, ed. Madison, WI: American Society of Agronomy; 1977: 462.

2 Cole NA, Rush CM, Green LW. Influence of corn smut on the palatability and digestibility of corn silage. Prof. Anim. Sci. 2001;17:287-294.

3 Rankin M. Smut in the corn field. University of Wisconsin Extension. Published Oct. 14, 2012. https://fyi.uwex.edu/aroundthecorn/smut/. Accessed Sept. 23, 2016.

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