While the cool, wet conditions across most of Iowa have helped alleviate drought, they have interfered with cover crop (CC) termination ahead of planting. We normally recommend terminating CCs with a herbicide application at least 10 days before planting corn – because corn is a “princess” and there is more risk and potential issues when planted green (i.e. cover crop terminated at or after corn planting).

Planting green is associated with reduced corn yield.

Pesticide labels are changing to better protect endangered species. This means applicators will want to carefully review pesticide labels for substantial changes this year and into the future. For more on the background of these label changes, check out the Herbicides and The Endangered Species Act page from the Weed Science Society of American or this article on the Endangered Species Act written by Bill Chism, a retired senior biologist with the EPA.

Southern rust is a leaf disease of corn that is caused by the fungal pathogen, Puccinia polysora. The disease is recognized as clusters of small, circular (1/16” diameter) spots that produce thousands of bright orange urediniospores on the upper side of the leaf (Fig. 1). With southern rust, there are multiple disease cycles during the growing season.

In 2025, the effect of commercial fungicides on foliar diseases of corn were evaluated at six ISU Research and Demonstration Farms: Northwest Research Farm (NWRF), Northern Research Farm (NRF), Northeast Research Farm (NERF), Armstrong Memorial Research Farm (lost due to wind damage before tasseling), Ag Engineering and Agronomy Farm (AEA), and Southeast Research Farm (SERF). Fungicide products evaluated and timing of application are shown in Table 1.