When you plant corn on corn, you better have a good disease package in the hybrids. That's the message Dave Nanda , Brid Hybrids, LLC., is trying to relate to farmers this season. Some of the cases he's finding in fields in certain parts of Indiana are making his point for him.

"The other point I want farmers to understand is that just because you have hybrids with insect protection, even Bt for corn borer and for corn rootworm, found in popular triple stacks, doesn't mean there won't be diseases issues," he insists. The triple sack traits have nothing to do with preventing disease, he adds.

Some might argue that if insects don't attack, plants may stay healthier. You could build a case that there will be less entry points for stalk rot later in the season. However, Nanda refers to the hybrid's ability to fend off foliar diseases when environmental conditions favor the disease. Visiting farmers in Sullivan County last week, where conditions have been warmer than in some other parts of central and northern Indiana, he didn't even find rust that has popped out in many areas of the state. Instead he found gray leaf spot, a more serious foliar disease, especially if it gets a foothold on or above the ear leaf before the crop is far enough along to minimize yield loss.

"The field I found it in first was planted early," he says. "So it will probably be OK. There were some lesions above the ear leaf, but the crop was fairly far along. However, I suspect it will be a problem if conditions stay the same weather-wise in late-planted corn there."

The earlier a disease gets a start, the odds are greater that it can do more damage. The inoculum is present in the soil, and can take hold once conditions are right. It's magnified in corn after corn fields, because there is often more inoculum near the surface.

Nanda is also noticing more diplodia ear rot this summer. "We've been noticing more of it in the past few seasons," he adds. "It's making a comeback. However, there were still only a small percentage of the plants affected."

Surprisingly, in one field Nanda found that the non-Bt refuge corn was much healthier than the triple stack corn next to it. "It was all because that hybrid has a good disease package," he says. "Insects didn't bother it, and it apparently had more built-in genetic power to resist disease than the triple stack planted on the majority of the field."

The plant breeder hopes farmers take home two messages from his recent travels. First, if you're going to plant corn after corn, be sure the base genetics has good resistance and tolerance to key diseases, including gray leaf spot. That can be more important than whether it's a triple-stack hybrid or not.

Second, look beyond the high price tag and fancy advertising for triple stacks, and study the chart the seedsman can provide about disease packages. Not every triple-stack hybrid has excellent resistance to all diseases, he notes. In some parts of Indiana, thanks to the right environmental conditions, that is already becoming painfully obvious this year, he concludes.