Environmental Drivers of Maize Ear Rots and Mycotoxin Accumulation Across North America

Maize is susceptible to ear rot and at risk for mycotoxin accumulation. Fungal colonization and mycotoxin contamination impact grain quality and pose serious health risks. In North America, the most prevalent maize ear rots are Gibberella ear rot (GER), Fusarium ear rot (FER), and Aspergillus ear rot (AER). FER is associated with fumonisin (FUM) contamination and AER with aflatoxin (AFL) contamination. Weather patterns have shifted, and an updated assessment of ear rots and their drivers will guide prioritization of threats to grain quality. Two hybrid panels with varying levels of resistance to ear rot pathogens were screened in highly replicated trials across a range of North American environments. We evaluated one panel for ear rot incidence (n = 108 hybrids) and the other panel (n = 4 hybrids) for mycotoxin accumulation. FER and FUM were the most prevalent disease and toxin, respectively. FER was more common in southern environments, while GER occurred in northern environments. FER and FUM were present in northern environments, including FUM above advisory levels. Insect damage was related to FER and GER incidence. Cool, moist conditions favored GER development, while warm environments were conducive to FER and FUM. Post-silking environmental conditions were important for GER and AFL, while pre-silking conditions were also important for FER and FUM. Despite different epidemiological drivers, GER and FER were observed in overlapping environments. Breeding for resistance to multiple ear rots, integrating epidemiology and plant breeding, and managing environmental stress are crucial for effective ear rot management.