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Effect of a foliar fungicide applied at flowering on corn standability at harvest

Alison Robertson: Iowa State University, Department of Plant Pathology

<div>In the U.S. Corn Belt, foliar fungicide applications on corn have increased over the past decade. Some farmers have observed that corn that is treated with a fungicide at flowering is less susceptible to lodging prior to harvest. Field trials were established at six Iowa State University Research and Demonstration farms in 2017. Each field trial was set up as a 2 × 5 factorial randomized complete block design. Plots were either sprayed with a fungicide at growth stage R1, or left unsprayed. Plots were harvested on 5 dates, each separated by 4 to 7 days, starting when grain moisture was approximately 23%. Immediately prior to harvest, the push test was done on 100 consecutive plants in each plot and percent lodging was recorded. No fungicide × harvest date interaction was detected on lodging. Percent lodging increased with later harvest dates (P<0.01). At 4 of the 6 locations, a fungicide application reduced percent lodging (P<0.01). These data suggest that when harvest is delayed, farmers should harvest plots with no fungicide prior to fungicide-applied plots due to the greater risk for poor standability and difficulty harvesting in those fields with no fungicides.</div>