Where’s DON? Understanding Where Deoxynivalenol (DON) Accumulates in Corn Silage

Maxwell O. Chibuogwu, University of Wisconsin-Madison; Brian Mueller, University of Wisconsin-Madison; Carol L. Groves, University of Wisconsin-Madison; Albert U. Tenuta, Ontario Ministry of Agriculture, Food and AgriBusiness; Martin I. Chilvers, Michigan State University; Kiersten A. Wise, University of Kentucky; and Damon Smith, University of Wisconsin-Madison.

Summary

• The fungus Fusarium graminearum is responsible for Gibberella ear rot and Gibberella stalk rot and the contamination of silage with deoxynivalenol (DON) in both brown midrib hybrids (BMR) and conventional hybrids.

• Colonization and production of DON by F. graminearum in ears and stalks of corn plants can differ between hybrid market classes (BMR vs. conventional hybrids).

• During the first month of fermenting (ensiling), the modified form of DON, deoxynivalenol-3-glucoside (DON3G), can be converted from an undetected form to DON, thus enabling detection using routine methods and partially explaining an increase in DON in stored corn silage.

• Breeding efforts for corn silage hybrids should focus on F. graminearum resistance in both the stalks and ears.

• Future mycotoxin testing should focus on methods that can detect all forms of DON.

Introduction

Whole plant corn silage (WPCS) is an important dry forage source for milk production in dairy cattle (Haerr et al. 2015; Shaver and Kaiser 2011). Brown midrib (BMR) hybrids are more digestible  when compared to conventional hybrids. In both types of hybrids, susceptibility to stalk and foliar disease is a significant problem as no corn hybrid is totally resistant to all diseases, including ear rots.

Gibberella ear rot (GER) and Gibberella stalk rot (GSR) are caused by Fusarium graminearum and are significant problems faced by corn and dairy farmers (Figure 1). These diseases reduce corn yield and the causal fungus can produce the mycotoxin deoxynivalenol (DON), also known as vomitoxin.

The adverse effects of DON in animal diets are well documented, but toxin production in silage corn and the role DON and its byproducts play in the ultimate toxin concentration have not been well studied. There is also more than one form of DON. An example includes DON-3-glucoside (DON3G), which plants produce as a defense response during F. graminearum infection. DON3G goes undetected (masked) by routine laboratory tests that detect DON. Although DON3G is less toxic than DON (Berthiler et al. 2009), its contribution to total DON levels and its fate during ensiling is largely unknown.

Efforts to reduce DON in corn hybrids can include corn and wheat residue management, rotation with other crops that aren’t a host of F. graminearum, hybrid selection for resistance, and foliar fungicide use. Foliar fungicide applications are beneficial for above-ground diseases but are mostly ineffective for stalk rots (Peltier et al. 2015; Price et al. 2018). Fungicide companies have recommended in-furrow fungicide application as an effective strategy to control soilborne pathogens that cause stalk rots (Keyes 2015; Pierson et al. 2018). However, results from in-furrow fungicide applications have not been consistent.

Understanding the role and impact of DON and its alternative forms at harvest and during ensiling is crucial for ensuring healthy diets and feed safety for dairy animals. It is also important to understand best management practices for reducing DON in silage.

Research Goals

• Evaluate the presence and relationship of F. graminearum and DON in ears and stalks of BMR and conventional hybrids and understand their susceptibility to the fungus and subsequent toxin production.

• Evaluate the impact of in-field fungicide applications on the concentration of DON during the fermentation process (ensiling).

• Track the concentrations of DON and DON3G during ensiling of BMR and conventional hybrids.

The Research

In 2020 and 2021, field trials using a BMR silage corn hybrid and conventional silage corn hybrid were conducted at the Arlington Agricultural Research Station (ARS) in Arlington, Wisconsin. The field trials evaluated the effect of foliar (applied at silking (R1) growth stage) and in-furrow (applied at-plant) fungicide treatments (Table 1) on foliar disease, ear rot, stalk disease, and DON concentration. The prevalent foliar disease present in both years was tar spot. Additionally, freshly chopped whole-plant corn silage samples were analyzed for quality, nutritional parameters, and DON concentration. Another field trial using a BMR and a conventional hybrid was also conducted in 2020 and 2021 at Arlington ARS to determine the impact of in-season management practices on DON accumulation within the two silage corn hybrids ensiled over five time points (harvest and 30, 60, 90, and 120 days after harvest).

Table 1. Product name, active ingredient (a.i.), application rate, Fungicide Resistance Action Committee (FRAC) code, growth stage of application, date of application, and the company that produces each fungicide product used on the brown midrib and conventional hybrids of corn in 2020 and 2021.

Results from the first trial indicated there was inconsistency in how fungicide treatments affected the measured silage quality parameters (digestibility, lignin, moisture, starch, and milk production potential) across the years and hybrids tested. Hybrid choice significantly influenced yield, silage quality, and tar spot severity (Table 2). F. graminearum and DON concentrations were consistently lower in the ear of the conventional hybrid compared to stalks of the same hybrid and both the ear and stalks of the BMR hybrid (Table 3). An increase in fungi detected resulted in an increase in DON concentration in the ears of both hybrids, however this relationship was not observed in the stalks. The concentration of F. graminearum DNA present in the ear of the conventional hybrid was also significantly lower than its stalks and both stalks and ears of the BMR hybrid (Table 3).

Results suggest that hybrid class (BMR vs conventional) drives much of the differential DON accumulation between the ear and the stalk. In this analysis, DON concentration between both hybrids in WPCS (Table 2) was driven chiefly by fungal colonization and accumulation of DON in the ear (Table 3).

Table 2. Silage quality indices, dry matter yield (DM), tar spot severity, and deoxynivalenol (DON) concentration in conventional (B08J81AMXT™) and brown midrib (B10B77SX™) hybrids.

¹Means calculated for each plot were used in the analysis; ²aNDF: Neutral Detergent Fiber. The ‘a’ in aNDF indicates that amylase was added in the analyses to help clean up the residue; ³ TTNDFD: Total Tract Neutral Detergent Fiber Digestibility; ⁴Milk production prediction in kilograms per tonne of dry matter. Based on the MILK2006 performance calculator (Shaver 2006); ⁵Values (means and standard errors (SE)) are back transformed from the lognormal distribution using the Omega method; and ⁶Tar spot severity was visually assessed as the average symptomatic percentage of ear leaves with the aid of a standard area diagram.

Table 3. Concentration of deoxynivalenol (DON) and Fusarium graminearum DNA in the stalk and ear parts of corn plants harvested from both a BMR hybrid (B10B77SX) and a non-BMR hybrid (B08J81AMT) in 2020 and 2021.

¹Means reported here are back-transformed from the log-normal for clarity. Means with the same letter are not significantly different within hybrid based on Fisher’s least significant difference (α = 0.05) test.

Results from this research demonstrate that hybrid class and ensiling duration were key in determining DON concentration within silage. DON concentration was lowest at harvest compared to the other durations of ensiling (Figure 2). The period between harvest and 30 days of ensiling had the greatest incremental change in DON concentration. During that period, when the concentration of DON was low, the concentration of its modified form DON3G was high and vice-versa. This pattern was observed both at harvest and after 30 days of ensiling. Analysis of the relationship between both compounds shows that the amount of DON3G at harvest influences the amount of DON after 30 days of ensiling (Figure 3). Knowing how much DON3G is present at harvest can be used with some accuracy to predict how much DON might be in the silage 30 days later. In addition, some DON accumulation is also likely from fungal production in the early days of ensiling before anaerobic conditions prevail.

Conclusions

Fungicides were inconsistent in protecting silage quality and reducing toxin accumulation from silage corn. GER and GSR occur independently, with significant differences in toxin accumulation between them. Hybrid selection is critical to meet milk production goals and for ensuring good quality and low toxin levels in silage corn. It is also important to understand that DON can accumulate in both ears and stalks but is often at lower concentrations in ears of conventional hybrids. The first 30 days of ensiling after harvest are critical in terms of DON accumulation in silage. The early stages of ensiling can be conducive to fungal growth and toxin production; plus, when metabolized during ensiling, alternative forms of toxins that might otherwise not be detected, can substantially contribute to final toxin accumulation. For fields with recurring, consistent DON issues, it is recommended to plant conventional hybrids, integrate cultural control methods, and apply fungicides for foliar diseases with an understanding they will do little for ear and stalk rot problems. Estimating DON3G and other derivatives at harvest can provide insight into the increase in DON concentration at feeding.

This research update is based on the work described in the following peer-reviewed research articles: 

Chibuogwu, M.O., Groves, C.L., Mueller, B., and Smith, D.L. 2024. Effects of fungicide application and corn hybrid class on the presence of Fusarium graminearum and the concentration of deoxynivalenol in ear and stalk parts of corn (Zea mays) used for silage. Plant Dis. Article | Google Scholar

Chibuogwu, M.O., Mueller, B., Groves, C.L., and Smith, D. 2023. Impact of fungicides on dual-purpose and brown midrib Zea mays hybrids used for silage in Wisconsin. Plant Health Prog. 24:462–467. Article | Google Scholar

Chibuogwu, M.O., Reed, H., Groves, C.L., Mueller, B., Barrett-Wilt, G., Webster, R.W., Goeser, J., and Smith, D. 2024. Influence of hybrid class and ensiling duration on deoxynivalenol accumulation and its derivative deoxynivalenol-3-glucoside while ensiling corn for silage. Plant Dis. Article | Google Scholar

References

Duringer, J.M., Roberts, H.L., Doupovec, B., Faas, J., Estill, C.T., Jiang, D., and Schatzmayr, D. 2020. Effects of deoxynivalenol and fumonisins fed in combination on beef cattle: Health and performance indices. World Mycotoxin J. 13:533-543. Article | Google Scholar

Haerr, K.J., Lopes, N.M., Pereira, M.N., Fellows, G.M., and Cardoso, F.C. 2015. Corn silage from corn treated with foliar fungicide and performance of Holstein cows. J. Dairy Sci. 98:8962–8972. Article | Google Scholar

Keyes, C. 2015. Fine-tune the furrow. Progressive Farmer. Online publication.

Mueller, D., Wise, K., and Sisson, A. 2023. Corn disease loss estimates from the United States and Ontario, Canada – 2022. Crop Protection Network. Article

Peltier, A.J., Mansfield, B.D., and Johnson, M.L. 2015. Comparison of fungicide products and application timings (in-furrow, V6 R1) for corn disease management and yield in Monmouth, Illinois in 2014. Plant Dis. Manage. Rep. 9:FC131. Article

Pierson, W.L., Kandel, Y.R., Allen, T.W., Faske, T.R., Tenuta, A.U., Wise, K.A., and Mueller, D.S. 2018. Soybean yield response to in-furrow fungicides, fertilizers, and their combinations. Crop Forage Turfgrass Manag. 4:170073. Article | Google Scholar

Price, P., Parvis, M.A., and Washam, P.S. 2018. Effect of fungicide application timing of southern rust, lodging and yield, 2017. Plant Dis. Manage. Rep. 12:CF191. Article

Shaver, R. and Kaiser, R. 2011. Top producing dairy herds in Wisconsin feed more forage than you may think. Google Scholar

Acknowledgements

Authors

Maxwell O. Chibuogwu, University of Wisconsin-Madison; Brian Mueller, University of Wisconsin-Madison; Carol L. Groves, University of Wisconsin-Madison; Albert U. Tenuta, Ontario Ministry of Agriculture, Food and AgriBusiness, Martin I. Chilvers, Michigan State University; Kiersten A. Wise, University of Kentucky; and Damon Smith, University of Wisconsin-Madison.

Reviewers

Travis Faske, University of Arkansas and Adam Sisson, Iowa State University.

Sponsors

This work is supported by the Hatch Project, project award no. WIS03076, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.