Corn disease's impact varies across region

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OCT. 09, 2013

The hot, dry growing conditions that frustrated many corn farmers for the last two years may have had at least one positive effect: A corn disease that reached peak levels in 2011 largely spared many Midwestern corn growers this year.

Goss’ wilt, which is caused by a bacterium, had been confined to eastern Colorado and western Nebraska for decades until about 2008. That’s when it moved eastward, affecting farms across the corn belt. Iowa State University plant pathologist Alison Robertson says modern hybrid corn varieties may be to blame for the resurgence.

“If you’re breeding for yield, then often times you’ll lose something along the way,” Robertson said. “And I think that in this case, we lost resistance to Goss’s wilt. Because Goss’s wilt wasn’t a widespread problem, the breeders didn’t pick up on that these hybrids were very susceptible.”

Resistance was bred into some hybrids used on the windy plains and in the sandy soil of western Nebraska and eastern Colorado because those factors made the region vulnerable. The bacterium that causes the disease needs an open wound on the plant to infect it.

Incidents of the disease have been significantly lower in Iowa the past two years, which Robertson said is thanks in part to the dry conditions and part to adoption of resistant hybrids. But this summer was especially hard on parts of Nebraska, even with the resistant varieties.

“It was really a major problem this year, particularly in storm-damaged areas like we had in this area of the state,” said Jenny Rees, a University of Nebraska extension specialist in Clay County.

Rees said early-season storms struck young corn plants whose defenses were not yet mature.

“So even though these different hybrids had resistance to Goss’s wilt, they had a systemic version in which it gets in the stem and basically kills that plant outright,” Rees said. Rees said on one farm she saw nearly two-thirds of a field wiped out by Goss’s wilt.

Robertson said in addition to using the resistant hybrids, farmers can reduce the likelihood of Goss’s wilt by planting soybeans or alfalfa in rotation with corn, rather than growing corn year after year. The bacterium that causes Goss’s wilt can survive up to 18 months after the corn it infected has been harvested. That means it could be alive in the silage when the farmer returns to the field the following spring. Robertson said the bacterium does not pose a threat to other crops.

Even as its occurrence in some corn belt states has diminished, Goss’s wilt continues to infect new places—spreading into Louisiana for the first time this year.

“This disease is still continuing to pop its head up at places where it shouldn’t be popping its head up,” Robertson said, “and so we need to whack the mole.”

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