EAST PEORIA, Ill. — Knowing the differences among common foliar diseases in corn, and how to treat corn pathogens including Goss’ wilt, was the topic of a presentation from University of Illinois associate professor of plant pathology Carl A. Bradley during the Corn and Soybean Classic Jan. 7.

Bradley noted high levels of foliar disease can lead to lower yields, stalk rot, lodging and other issues that can cause economic yield losses.

With Goss’ wilt on the rise in the state of Illinois since 2009, farmers will want to consider planting corn hybrids with higher levels of resistance to the bacterium, rotating to non-host crops and increasing tillage in order to facilitate decomposition of diseased residue, Bradley urged.

The reason: There are no known in-season control options available to protect against the spread of Goss’ wilt in the field, according to field trials of products purported to control the disease conducted by U of I researchers.

But before farmers can begin to form a management plan to combat a foliar disease, they must be able to positively identify the particular bacterium.

“You’ve got to be able to recognize the disease,” said Bradley, noting Goss’ wilt is characterized by large tan to gray lesions with dark spots, or freckles, within the lesions on a corn leaf. “I have photos sent to me by producers that are identified as (pictures) of Goss’ wilt, but are not.

“If you are unsure, it’s important to get another opinion, such as sending samples to the University of Illinois plant clinic, where they can do a bacterial screening under a microscope.”

Once a sample has been positively identified as Goss’ wilt, a course of action may be determined by producers, often after consultation with a plant pathologist, crop advisor or other crop disease expert.

“I think that resistant hybrids are the No. 1 way to manage this disease. In the late 2000s we didn’t have very many resistant hybrids. There were a lot of very susceptible hybrids out there that have left the marketplace and been replaced by products with higher resistance,” said Bradley.

“Rotation is obviously important as well. We always see this disease first in fields that were corn-on-corn or had been for many years. Tillage, to break up the residue, can also be an important component.” Fungicides will not be effective in combating Clavibacter michiganensis, which causes Goss’ wilt.

“Northern leaf blight (NLB) was also a real issue for producers in 2014,” he continued, switching slides to show a photo of a Saline County corn field inundated with NLB. “I almost slammed on my brakes when I came across this field in southeastern Illinois. Believe me, you don’t want to be tailgating a plant pathologist when he’s driving down the road.”

The southern Illinois field was “hammered” by NLB, Bradley said. “I couldn’t have produced this kind of disease pressure if I had inoculated my whole field with NLB.”

NLB, caused by the fungus Exserobilum turcicum and identified by tan-colored, cigar-shaped lesions that are long and tapered, should be addressed by producers with an array of management practices. They include planting resistant hybrids, applying foliar fungicides, rotating to non-host crops and increasing tillage, he advised.

He could not stress enough the importance of scouting and positively identifying various foliar diseases in corn plants. Depending on the particular disease, resistant hybrids, crop rotation and foliar fungicides may be available to help manage Goss’ wilt, NLB, gray leaf spot and other foliar maladies, according to Bradley.

“The more effective your inspections are, the greater chance of reducing economic losses from foliar diseases,” he explained.