By Andi Anderson
Corn fungicide use across the Midwest has increased in recent years, especially after tar spot became more common. While many farmers noticed yield benefits, the reasons behind these gains were not fully understood. New research from Purdue University now explains why fungicides can improve corn yields when used correctly.
A two-year study conducted across three locations in Indiana compared untreated corn fields with those receiving at-plant and R1 foliar fungicide applications. The R1 stage, which occurs at silk emergence, proved to be the most effective timing. Researchers found that foliar fungicide applications at R1 reduced disease severity by up to 84 percent and extended the grain-fill period by three to five days.
“Sometimes we had to conduct sampling every week and be careful how we sampled the kernels,” said Quinn, an assistant agronomy professor at Purdue. “People have done this before with nitrogen and temperatures. It seemed like we thought we were seeing similar responses with fungicides, but we also were diving into the why, and it was trickier doing that.”
Extending the grain-fill period allows corn plants to continue photosynthesis longer. This leads to heavier kernels and higher final grain yields. By protecting the green leaf area, fungicides help plants maintain energy production and move more nutrients into developing kernels.
The study also showed that fungicide benefits are strongest when disease pressure is present. Locations with higher levels of tar spot, gray leaf spot, northern corn leaf blight, and southern rust saw clearer yield improvements. Where disease levels were low, yield gains were limited.
Researchers stress that fungicides should be used as part of an integrated pest management approach. This includes selecting disease-resistant hybrids, scouting fields before tasseling, monitoring weather conditions, rotating fungicide modes of action, and applying products only when needed. Overusing fungicides may increase resistance risks and reduce their effectiveness in the future.
Cost remains another key factor. Some fungicide applications can cost between 30 and 40 dollars per acre. With corn prices near four dollars per bushel, growers may need yield increases of more than ten bushels per acre to cover treatment costs. This means fungicides will not be profitable in every field or every season.
Tools such as corn fungicide return calculators can help farmers and crop advisers decide whether an application is cost-justified. Overall, Purdue’s findings provide clear evidence that well-timed fungicide use can improve corn yields, but only when disease risk and economic conditions support the investment.
Photo Credit: gettyimages-songdech17.
Categories: Indiana, Crops, Corn, Soybeans