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Blue Eye Mold Threatens Stored Grain

July 26, 2017

Due to a combination of temperature and humidity last fall, producers need to be aware of the high risk of blue eye mold, a fungus that grows on corn kernels.

Blue eye mold appears as a blue line down the middle of a corn kernel, where the germ is located. The fungus invades the kernel and feeds on the high fat oil located in the germ. There is no way to get rid of blue eye mold, but there are ways to control its spread.

Carbon dioxide monitoring is one way to observe corn conditions in bins. However, blue eye mold does not grow at a fast enough pace to give off a detectable amount of heat.

“Aerating the corn with humid air, like what the state has been experiencing recently, will make the mold grow,” said Charles Hurburgh, grain quality and handling specialist with Iowa State University Extension and Outreach. “If the dew points get down to the 40s and 50s relative humidity then fans should be run. Additionally, grain that is still cold from the winter should not be warmed.”

Although feed mills and ethanol plants can use the moldier corn, blue eye kernels are graded as damaged. If feeding it to animals, mix with sound corn at a reasonable amount for the species consuming it.

An elevator will purchase blue eye kernels and count them as damaged. Typically, the grading limit on number two yellow corn has a maximum of five percent damaged kernels.

Ethanol plants may buy corn affected by blue eye mold, although they prefer not to as the risk for having a fermentation problem is higher. The fermentation may not be as clean because the mold interferes with the yeast. Fermenters can get stuck, requiring corrective antibiotic use.

“With a two billion bushel surplus for this year, some of this corn is going to last into 2018. Ideally this fall, sell the old corn and replace it with the new in the bins,” said Hurburgh.

For more information about the Iowa Grain Quality Initiative, visit

Source: Iowa State University