Foliar Fungicide Effects On Corn Yield: A Survey of On-Farm and University Trials.

Generally positive yield responses have driven increased use of foliar fungicides by corn growers. To improve understanding of the value of foliar fungicide use in corn, a survey was conducted of corn yield response to fungicides in Pioneer side-by-side field trials and university research trials. The average yield response across 356 on-farm trials and 74 university trials to the application of a fungicide was an increase of 7.4 bu acre^-1. A positive yield response to fungicide application occurred in 80% of the trials, however economic viability can vary greatly according to the price of corn. The yield advantage with a foliar fungicide application was greater with hybrids less resistant to gray leaf spot, at sites with significant disease pressure, and with agronomic practices that favor high levels of crop residue on the soil surface. For hybrids moderately resistant to gray leaf spot, the average yield increase was approximately 8 bu acre^-1 in corn following corn and 6.5 bu acre^-1 in corn following soybean. The average yield response for resistant hybrids however, was less than 4 bu acre^-1. The presence of significant disease pressure resulted in an average yield response that was over four-fold greater than at sites with low severity. In corn following corn, the average yield advantage with fungicide application was 8.9 bu acre^-1 in no-till or strip-till, 8.2 bu acre^-1 in conservation tillage, and 5.9 bu acre^-1 in conventional tillage. In corn following soybean, the yield advantage in no-till or strip-till was 9.5 bu acre^-1. The average fungicide yield response in conservation and conventional tillage would not be economically beneficial in most cases, with average yield responses of 4.4 bu acre^-1 and 2.7 bu acre^-1 in the two tillage systems, respectively.