Over the span of just a few years, in-season fungicide applications have gone from a mostly new practice to a trusted component of many farmers’ management systems. Research results and grower experience have demonstrated that fungicides can be effective tools for managing foliar diseases, such as Northern corn leaf blight and Southern rust, and helping to protect corn yield. For many Southern U.S. growers, corn will soon reach VT-R2, where fungicides can help to fight off disease when needed most – between tasseling and brown silk.
“When we think about scouting our fields, we want to get out early and often,” said Eleanor Aufdenkamp, a Pioneer Field Agronomist in Southeast Texas. “As we’re scouting, keep an eye out for lesions and, most importantly, where that ear leaf will be. That ear leaf will be our most important leaf as we go through pollination and into grain fill.”
Disease pressure is a crucial factor determining the value of a foliar fungicide application. Most widely-grown hybrids have at least moderate resistance to major leaf diseases, which may be sufficient protection against low to moderate disease pressure. However, in years when weather conditions are very conducive for disease, a fungicide application may provide a substantial economic benefit.
Fungicide timing is also important. Foliar infections can occur at any growth stage. The earlier lesions develop, the more leaf area is reduced and the more damage results. However, plants are generally more susceptible to infection after silking. A well-timed fungicide application can prevent damage and protect yield potential.
“Pick fungicides with multiple modes of action,” advised Aufdenkamp, “You’ll want a preventative as well as a curative type of chemistry, as well as a residual that can get you through that pollination stage and into grain fill.”
Continuous corn and minimum tillage fields may require additional attention, as these fields can be at a higher risk of disease and are more likely to benefit from a fungicide application.