Occurrence and associated agronomic factors of mycotoxin contamination in silage maize in the Great Lakes region of the United States

Silage maize in Michigan and the Great Lakes region is exposed to in-field ear and stalk rot fungal infections by Fusarium spp. which may result in production of toxic secondary metabolites called mycotoxins. These toxins can cause severe health complications in livestock but might remain unidentified as most silage maize is fed on-farm and not sold in formal markets. This study was conducted to quantify the status of mycotoxins and the agronomic management practices impacting their concentration in silage maize across Michigan farms. Samples (n = 122) were collected from across the state for three years (2019-2021). Results show that 100% of the samples tested positive for deoxynivalenol (DON) at detectable levels. Other mycotoxins that occurred frequently were zearalenone (ZEN), fumonisins, enniatins, and beauvericin (BEA). Mycotoxin concentration was found to vary across regions due to differences in weather parameters such as temperature and humidity, driven partly by the proximity of some regions to the Great Lakes. Mycotoxins were also found to co-occur, with an average of 13 mycotoxins in each sample. Strong correlations were observed between DON, ZEN, and BEA (r > 0.40). Crop rotation and planting date explained 91 and 68% variability in DON and fumonisin, respectively. Deoxynivalenol and fumonisin concentration was 20 and 67% higher in silage maize following a host crop of Fusarium spp. than a non-host crop. Planting silage maize between May 10 and May 30 increased the mycotoxin concentration by at least 50% than outside this window. However, tillage did not significantly impact mycotoxin occurrence and concentration. Overall, multiple mycotoxins were found in silage maize across the region and knowledge of their presence and contributing factors can help growers develop integrated management strategies to mitigate mycotoxin accumulation.