Foliar Diseases Warranting Fungicide Applications

The warm, wet conditions we have experienced over the last week are increasing disease pressure. If you have not applied a fungicide, you might be questioning whether or not to make an application. Agronomic returns from foliar fungicide applications can vary depending on the hybrid, application timing, disease pressure and weather.

Corn foliar diseases
We are concerned about northern corn leaf blight (NCLB), gray leaf spot, common rust, and southern rust in corn. NCLB has long, narrow, tan or grayish lesions. Gray leaf spot starts out as small pinpoint lesions surrounded by yellow halos which develop into long rectangular lesions as the disease progresses on susceptible hybrids. Gray leaf spot can be found on leaves, leaf sheaths and husks. Common and southern rust are similar in appearance, this Purdue Extension handout is helpful in distinguishing between the two. Southern rust has small, densely clustered, round to oval, light orange colored pustules; whereas common rust has larger pustules, scattered in streaks, which are elongated, and brick-red in color. Common rust will be found on both upper and lower sides of the leaf, whereas southern rust will be only on the upper leaf surface. Common rust is indeed quite common this year, and is usually not very important economically. Southern rust is potentially much more damaging. Southern rust was confirmed in Parke County in Indiana (nowhere else in the state to date) and in a handful of counties in southwestern Kentucky. For questions on specific situations, contact your regional agronomist.

Soybean foliar diseases
Be on the lookout for septoria brown spot, bacterial blight and phytophthora in soybeans. Septoria brown spot symptoms are brown to black spots found in the lower canopy first but will most likely move up due to the wet, warm weather. Bacterial blight cannot be treated with a fungicide since it is a bacteria not a fungus. Phytophthora root and stem rot will kill plants, it can first be observed by a dark brown lesion at the soil line.

Field day season is here. Contact your local Brodbeck Seed sales representative for a field day near you and save the date for our annual Wabash field day that takes place Aug. 21-22 at our headquarters.

Terry, Dan, Rod and Dennis