Continuing heat and drought are withering corn crops across the Midwest, creating prime conditions for a fungus that produces a toxic carcinogen causing health problems in livestock, according to Purdue University researchers.

The fungus, Aspergillus ear rot, infects corn ears through silks or wounds. Fields most at risk, researchers said, were planted in late March or early April.

"Aspergillus ear rot is out there, but it varies greatly from field to field," said Kiersten Wise, a Purdue University Extension plant pathologist. "There is no field without some potential for the disease."

The U.S. Department of Agriculture regulates how much aflatoxin is allowed in livestock feed and corn for human consumption. Corn destined for humans and dairy cattle has the tightest limit, at 20 parts per billion. Corn destined intended to finish beef cattle can contain the fungus at concentrations up to 300 parts per billion.

Another blow
The news comes as yet another blow for Corn Belt farmers struggling with a summer of extremes. The U.S. Drought Monitor showed that 64 percent of the Lower 48 states were experiencing moderate to exceptional drought, a new record.

Earlier this week the USDA chopped projections for corn and soybean yields. New estimates suggest the nation's corn crop could top out at 10.7 billion bushels, down 13 percent from 2011 and the lowest yield since 2006.

Soybean production was forecast at 2.6 billion bushels, down 14 percent from last year. Prices jumped in the commodity markets for both crops.

With no sign that prices will fade any time soon, Purdue University Extension agricultural economist Chris Hurt warned that the livestock industry is in for a tough patch. "Cash flows are probably going to be negative for the most part," he said in a statement.

This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company. Contact editor Douglas Fischer at