It's late spring, and despite all of the challenges, you've produced a stand of corn with potential for an excellent yield—if things go well the rest of the season. But many corn diseases—including ear rots, such as Gibberella, Diplodia and Fusarium, and other residue-borne diseases—could be a bigger threat than usual this year because of all the inocula lying out in the field on old crop residue.

The high volume of old crop residue is the result of delayed tillage due to wet weather. "About 70% to 80% of corn diseases are carried over in crop residue,” says Farm Journal Field Agronomist Ken Ferrie.

You can fight back against disease pressures, and now is the time to plan your attack strategy.

Here's why Ferrie is urging farmers to be especially vigilant against disease this year: "The stage is set for corn diseases to increase,” he says. "The likelihood of disease is based on three conditions called the disease triangle—a susceptible host crop, the pathogen and the weather. If one leg is stronger than usual—inocula, in this case—the other conditions don't have to be as perfect in order to trigger an outbreak.”

As always, the overriding factor will be weather, says University of Illinois Extension plant pathologist Carl Bradley. "When we see less tillage, there will be more potential for inoculum,” he explains. "But with single-year rotations, such as corn and soybeans, there usually is enough of the host debris left in the field to carry on the pathogens.”

Here are eight steps you can take to control diseases:

1. Do your homework. "Learn all you can about the diseases you've been having trouble with,” Ferrie says.

"Understand the ideal conditions for each one to develop and its life cycle. Then you will know what problems to expect in 2010.

"Keep in mind that if residue management is recommended as a control measure, the disease organism is carried over in crop residue,” he adds.

2. Bone up on fungicides. "You must know what fungicide to apply for each disease, and when to apply it,” Ferrie says. "It's not a matter of simply applying whatever product your supplier happens to sell.”

Some fungicides are preventive in nature, which means they must be applied before a lot of disease damage has occurred. Others are curative, which means they can be applied later. "But all fungicides work best if they are applied at the early onset of disease,” Bradley says.

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