Corn (Zea mays L.) in Michigan and the Great Lakes Region is prone to biotic stresses resulting in unavoidable yield and quality losses. Infections by ascomycete fungi causing ear or stalk rots and foliar diseases (such as tar spot) have become a major concern for corn growers in recent years. Ear and stalk rots in Michigan corn are primarily a result of Fusarium graminearum and F. verticillioides infections. These fungi not only impact the yield but also produce toxic compounds (mycotoxins), rendering corn unsafe for livestock consumption. Therefore, one of the major goals of this dissertation was to evaluate mycotoxin occurrence in silage corn (whole-plant corn fed to cattle) and explore integrated management strategies such as hybrid selection, fungicide application, planting date, and seeding rate. Samples from growers across Michigan revealed that deoxynivalenol, zearalenone, and fumonisins are the most commonly occurring mycotoxins in Michigan silage corn. Multi-location field trials for silage corn from 2019-2022 showed that the use of effective Bt proteins (such as Vip3A) in hybrid trait selection prevent corn ear injury due to Lepidopteran insects (primarily western bean cutworm), limiting access to ear rot causing fungi, eventually reducing mycotoxin accumulation. Fungicide application reduced ear rot incidence only at two out of eleven site-years and had limited benefit when disease incidence was driven by insect injury. Planting silage corn in late-April to early May and avoiding very high seeding rate (>100,000 seeds ha-1) helped in escaping environmental conditions favorable to insect injury and fungal infections from coinciding with corn silking. Post-harvest ensiling studies showed that an infected silage corn is more prone to continued mycotoxin accumulation especially under low compaction density. Additionally, field trials were conducted for quantifying losses in forage or grain yield and nutritive value as impacted by foliar stresses (primarily tar spot). Evaluations of photosynthetic capacity showed that tar spot has an impact that is proportionally greater than the observed disease symptoms. Variability observed in photosynthetic response to tar spot severity among current hybrids would be useful in future germplasm selection for disease resistance. Overall, this dissertation emphasizes the use of in-field integrated management such as hybrid Bt traits, disease resistance, fungicide application, optimal planting date, and seeding rate as potential solutions to minimize corn yield and quality losses due to multiple biotic stresses.
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