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New Corn Disease Discovered in U.S.

21:09PM Sep 06, 2016

A new bacteria is making its way into cornfields across the Corn Belt. Bacterial leaf streak is so new to the United States, researchers at Kansas State University don’t know if it will impact this fall’s yields.

The disease was confirmed by the U.S Department of Agriculture-Animal and Plant Health Inspection Service on Aug. 26, 2016. At this time, APHIS plans on treating it the same was as other corn diseases, like Goss’s bacterial blight.

Researchers believe the disease came from South African corn, however it’s been linked to gumming disease of sugarcane. Because of the newness of bacterial leaf streak, researchers don’t know how it came to the United States. 

According to a survey conducted by APHIS, bacterial leaf streak has been found in nine states: Colorado, Illinois, Iowa, Kansas, Minnesota, Nebraska, Oklahoma, South Dakota, and Texas. 

Tan to brown streaks from less than an inch to several inches long appear on infected corn leaves. 

“To the untrained eye, the disease can look very similar to the common fungal foliar disease, gray leaf spot,” said Doug Jardine, plant pathologist at Kansas State University. “One diagnostic key is that bacterial leaf streak has narrow, wavy-edged lesions compared to gray leaf spot, which has very sharp, straight-edged lesions that follow the veins of the leaf. Sometimes the lesions occur close to the midrib; in other cases, they occur across the leaf blade.”

Another way to determine if corn is infected is to backlight the leaves. The light that passes through bacterial leaf streak is translucent.

So far, symptoms have been observed as early as growth stage V7 in corn. Lesions show up on lower leaves first, then spread to the upper leaves. Sometimes lesions extend the entire length of the leaf. 

While it isn’t known how the disease spreads, some believe it’s from movement in the field or wind from thunderstorms. 

At this time, options to manage the disease are limited. Because it is a bacterial disease, fungicides aren’t effective in treatment. 

“We do not know how long the bacteria can reside in old crop debris, but observationally, it can survive through the rotational year to soybeans,” said Jardine.