Grain experts say a toxic mold residue that attacked the 2012 US corn crop may become even more problematic this summer and fall as farmers blend off tainted corn supplies from storage. This is a concern in the petfood industry as manufacturers work to avoid contamination in their final products and minimize petfood recalls due to aflatoxin.

"As we get into summer, you are going to see the worst of it," said Doug Bartlett, co-owner of advisory company Midwest Farm Services. "We have tight corn supplies and when we get down to the nitty gritty, there is going to be a lot of the aflatoxin left over, and it will have to be blended off into the new crop."

According to Charles Hurburgh, agricultural engineering professor at Iowa State University who specializes in grain quality, aflatoxin is currently a significant concern in the US from eastern Kansas across northern Missouri, up to central and southern Illinois. As temperatures rise in the spring, the mold responsible for causing aflatoxin can be spread inside grain storage bins, which could create a second round of problems after the initial outbreak when crops are harvested.

"We've already seen some flourishing of the molds that can produce aflatoxin," said Max Hawkins, a nutritionist with Alltech. "Because corn is in short supply, everybody wants to get every kernel, everything they can out of the bin. As the bin is emptied, those damaged kernels tend to concentrate in the bottom area....There is ample aflatoxin present in many, many storage facilities."