Corn Yield Loss Estimates Due to Diseases in the United States and Ontario, Canada, from 2020 to 2023

Corn ( Zea mays L.) was planted on 375.1 million acres (151.8 million hectares) cumulative from 2020 to 2023 in the United States and Ontario, Canada. During these 4 years, 59.6 billion bushels (1.5 billion metric tons) of grain were produced, valued at 325.9 billion U.S. dollars (USD). Plant pathogens that cause diseases limit annual grain production and reduce associated economic returns while also increasing management costs to prevent potential losses. Plant pathologists representing 29 U.S. states and Ontario, Canada, were asked to estimate annual percent yield losses caused by 37 pathogens or pathogen groups through an online survey. Grain contaminated by mycotoxins was also estimated. According to survey results, estimated overall annual percent losses ranged from negligible in Texas in 2023 to 15.8% in Michigan in 2021 and averaged 3.0% across all surveyed regions for the 4-year period. Diseases reduced corn yield by an estimated 2.5 billion bushels (63.7 million metric tons) across participating locations, with tar spot (caused by Phyllachora maydis), Fusarium stalk rot (caused by Fusarium spp.), and plant-parasitic nematodes causing the most significant losses. The total estimated economic loss caused by diseases was 13.8 billion USD, and the average economic loss was 37.76 USD per acre (93.30 USD per hectare) across all years and locations. Survey data and the resulting analysis can help inform corn disease management and guide pathology education, policy, and research priorities among scientists, government representatives, Extension educators, and other stakeholders.