Why are agronomists talking about corn stunt, first found in the U.S. in Texas 60 years ago? The disease was confirmed in several states for the first time in 2024. Should you be worried about it? How can you guard against corn stunt?

Brad Hopkins and Jason Woodward, Pioneer agronomists, and Krystel Navarro, North American plant pathology lead for Corteva Agriscience, have the answers to those questions, plus more information about corn stunt.

Cause and vector. Corn stunt is caused by a tiny organism, Spiroplasma kunkelii. However, it is transmitted by a specific leafhopper that reproduces only on corn. “You may need a hand lens, but you can identify corn leafhopper by two distinct black spots on the head,” Woodward says.

Latin American disease. Historically, corn stunt was first noted in tropical regions and is more typically a problem in Brazil and Latin American countries. Found in Texas in the 1940s, Woodward notes that it was thought to be caused by a virus until Spiroplasma was determined to be the cause in the 1970s. Other causal agents are likely involved with corn stunt in Brazil, where it is referred to as corn stunt complex.

Corn stunt in ’24. The disease was confirmed for the first time in several states: northwestern Illinois, Kansas, Minnesota, Missouri, Nebraska, Oklahoma and New York, where Cornell reported it, but noted there was no yield impact.

Related:Corn disease identified for first time in Missouri

Why in ’24? It is all about the movement of Dalbulus maidis, the leafhopper that reproduces specifically on corn, Hopkins says. Hurricane Beryl moved up through the Southern U.S. early in the ’24 hurricane season. The theory is that these tiny leafhoppers rode air currents northward.

“It was very warm in Texas then, and corn was available for feeding,” Navarro adds. Although the corn leafhopper will feed on a few other grasses, it prefers corn and does not have another primary alternate host.

Leafhopper life cycle. Average life cycle for the leafhopper is 24 days, Hopkins says. Each female can lay 15 eggs per day, so the population can build quickly. Because it prefers a warmer climate and needs corn to reproduce, it should not overwinter in states where corn is not available year-round and temperatures are below survival rate for the leafhopper.

Corn stunt symptoms. Reddening of leaf tissue and stunting are primary symptoms, Navarro says. More serious infection and stunting later in the season is more likely when corn is infected in early vegetative growth stages. When leafhoppers feed on corn and infection occurs late, reddening of tissue and less-invasive symptoms are more likely.

Related:Will disease stunt Argentina’s corn crop?

Potential yield loss. In South America, yield losses up to 25% have been reported, Hopkins notes. However, in the U.S., yield losses are likely much less, especially if feeding and infection occur later.

Cultural controls. Best management practices to avoid major issues include planting corn early, Hopkins says. That allows corn to get a head start. Second, focus on controlling volunteer corn in soybeans so it doesn’t become a host. Chemical control of leafhoppers in the U.S. is still difficult. The older the corn, the more difficult it is to spray and control leafhoppers.

 “Scout during the season,” Hopkins says. “And stay informed about this pest. Be aware of new information that may come out.”