Lowa State University Scientist is studying an emergent corn disease capable of reducing the yields of affected crops.

Alison Robertson, an associate professor of plant pathology and microbiology said that, Physoderma has reared its ugly head in Iowa cornfields with increasing regularity in recent years.

The disease, caused by the fungus Physoderma maydis, first appeared in India in 1910 and turned up in the United States in 1911. In the 1930s, the disease hit hard in southeastern states, leading to yield losses of 5 to 10 percent in the region. But U.S. farmers switched to seed varieties that were less susceptible to Physoderma, and the disease virtually disappeared until 2007, when Robertson began seeing brown spot symptoms. Stalk rot symptoms appeared in 2013. This year, the disease has popped up in dozens of fields throughout Iowa.

Robertson further said, Physoderma infects the entire corn plant but shows two different forms of symptoms.
The most noticeable is called Physoderma brown spot, which leaves distinctive discolorations on the leaves of the corn plant.
The other, known as Physoderma stalk rot, is more difficult to detect because it affects the lowest nodes of the stalk.

"The stalk rot usually doesn't show leaf symptoms," Robertson said. "It looks like a beautiful plant, and you don't notice it until the plant falls over and breaks." That breakage could occur during high winds or a rainstorm or it could occur during harvest, she said. Many of the infected plants won't yield any crop at all.

Plants with severe brown spot may not form ears, and, with stalk rot, fallen plants may not be picked up by a combine.