Mr. Jason Hartschuh, Extension Educator for Agriculture and Natural Resources, Crawford County, The Ohio State University Extension
2019 has been a difficult year in much of Ohio might be an understatement. We have corn tasseling in one field while right next to it in another field, or even in the same field, it is 2 feet tall. Many of the fungal corn disease we battle in Ohio show up late enough in the season that they cause little damage. With the late planting and harvest this year, how will that be different and what effect might it have on corn silage digestibility and mycotoxins. To learn more about Delayed Corn Planting the Disease Risk in Corn, visit last week’s CORN newsletter at: https://agcrops.osu.edu/newsletter/corn-newsletter/2019-23/delayed-corn-planting-disease-risk-corn.
When a fungal disease infects the plant, you often see a natural response to the disease of an increase in lignification of the fiber, which results in decreased NDF digestibility. The other challenge with fungal infections is that they may bring high levels of mycotoxins into the feed, but interestingly, the level of visual fungal disease symptoms does not correlate to the level of mycotoxins present. A study from the University of Illinois looked at treating silage corn with Headline or Headline AMP at V5 or R1 and the performance of Holstein cows compared to untreated corn. They used best management practices for disease selecting a corn variety with high levels of disease resistance. At the time of fungicide application, there were no diseases detectable. At harvest, mycotoxins were detected in the silage across all treatments, but levels were reduced for the fungicide applications, with greater reductions at the R1 treatment timing. Milk production was the same among treatments, but feeding the corn with lower mycotoxin concentrations (treated with fungicide) resulted in increased energy corrected milk and better feed efficiency due to lower dry matter intake when the corn for silage was treated with a fungicide.
Deoxynivalenol (DON) is one of the primary toxins of concern. It is caused by the fungus Fusarium graminearum and causes both Gibberlla stalk rot and Gibberlla ear rot, making it of concern for both the quality of the grain and forage. Over the last two years, Wisconsin has been working to better understand DON concentrations in silage. Interestingly, when they use a high quality BMR hybrid, they did not see any improvement in digestibility with the fungicide. The first year under low disease pressure, they saw that in all cases but one that an application of fungicide at R1 reduced DON concentrations by at least 50%. This R1 application window is from the start of silking until 10 days after. The trial was then expanded for 2018, which was a high disease pressure year with DON concentrations as high as 17.9 ppm in one hybrid and 30.3 ppm in the other hybrid. Again, fungicide had little effect on these two BMR hybrids yield or forage quality, but a few products did consistently lower DON concentrations. Interestingly the timing of application was not the same this time across all effective products. Proline at R1, Delaro at R2, and Miravis Neo at V6 all lowered DON concentrations, but concentrations were still over 7 ppm. The study also compared DON concentrations in the ears and the stalk. Interestingly the two hybrids were not the same; one had higher concentrations in the stalk and the other had higher concentrations in the ear. The ability to have high toxin level in the stalk means we will need to scout even late planted corn that may have low grain yields.
What does all this mean? First, there is still a lot of work needed in this area, but for DON control, the most common beneficial timing is R1 stage of growth. Scouting will be important in 2019, especially for late-planted fields, as there is increased potential for disease development, especially of diseases that do not over winter locally.
References
Smith, D., B. Mueller, and J. Goeser. 2018 Corn Silage Fungicide Trial Results: A Story of Vomitoxin
https://badgercropdoc.com/2018/10/12/2018-corn-silage-fungicide-trial-results-story-vomitoxin/
Haerr, K.J., N.M. Lopes, M.N. Pereira, G.M. Fellows, and F.C. Cardoso. Corn silage from corn treated with foliar fungicide and performance of Holstein cows. Journal of Dairy Science 98:8962-8972.