Corn Leafhoppers Active in South Texas

JEFFERSON CITY, Mo. (DTN) -- The corn leafhopper, a tiny flying insect capable of transmitting the potentially devastating corn stunt disease, survived the winter in South Texas and has been detected moving northward this month. Though the pest's presence is not yet of major concern, it reached the Midwest last year, so entomologists advise farmers to scout for corn leafhoppers early this season.

While a killing freeze did extend into portions of Texas in January, it failed to reach the lower Rio Grande River Valley, said David Kerns, Texas A&M University Extension entomologist. Scouting efforts revealed that the insects were active on volunteer corn plants in the region.

Within the past week, corn leafhoppers have been detected in two areas farther north in Texas, including Nueces County near Corpus Christi and Burleson County near College Station.

"Last year, in the [Rio Grande River] valley, the numbers didn't start really picking up to where they were noticeable until mid to late April," Kerns said. "This year, we're watching out for them."

CORN BELT CONCERN?

Historically, corn leafhoppers are a pest in Central and South America. The insect was first reported in the United States in the 1940s and was considered an occasional pest in parts of Texas, Florida and California.

But in 2024, the pest was detected in several states much farther north. Their movement was likely aided by the winds of Hurricane Beryl, which made landfall in Texas in early July. By August, entomologists in Missouri and Oklahoma reported corn leafhoppers, and by season's end, the insects had been found in several major corn-producing states, including Illinois, Iowa, Minnesota and Nebraska.

Corn leafhoppers impact corn health and yield both directly and indirectly, said Ivair Valmorbida, University of Missouri Extension entomologist. They cause direct damage to corn plants by feeding on leaves with their piercing-sucking mouthparts. As they feed, the insects excrete honeydew, which can lead to black sooty mold, impeding photosynthesis and negatively affecting plant health.

However, it's the indirect damage that's of greatest concern. Though no larger than a grain of rice, Valmorbida said corn leafhoppers can transmit both bacterial and viral pathogens associated with corn stunt disease, which can cause 100% yield loss. Corn stunt spiroplasma, a bacteria, is considered the predominant pathogen associated with corn stunt disease.

"When they feed on an infected corn plant, the leafhoppers can acquire the pathogens that cause corn stunt," Valmorbida explained. "Those pathogens will build up inside the insect, and then when that infected leafhopper feeds on a healthy corn plant, it can transmit the pathogen."

LIMITING YIELD LOSS

The range and severity of corn stunt symptoms can vary and are influenced by the corn's growth stage when infection occurs, the amount of inoculum present, the corn hybrid and environmental and weather factors, Valmorbida said.

"We know that the earlier the infection occurs, the younger the corn, the more likely we are to see yield losses," he explained. "If the leafhoppers show up around V5 and they're carrying the pathogens, there's a greater chance of the corn stunt disease to cause significant yield losses. If they show up later in the season after tasseling, that's not likely to cause any problem to corn in the field."

Kerns said currently in the Rio Grande River Valley, insecticidal seed treatments seem to be providing protection to commercial corn fields that have reached the V4 growth stage. Earlier this week, the USDA National Agricultural Statistics Service (NASS) reported 59% of corn was planted statewide in Texas.

Farther north in the Corn Belt, where corn planting hasn't yet started or is just underway, Valmorbida said neither corn leafhoppers nor volunteer corn are present following winter freezes. The insect requires a living host year-round as they do not truly overwinter. Although they will only reproduce on corn, corn leafhoppers have been noted feeding on other grass species such as gamagrass and Johnsongrass. They also have been found on alfalfa, triticale and other winter annual weeds, although there is no evidence of these plants serving as feeding hosts for corn leafhoppers.

As this season begins, Valmorbida offered the following tips to reduce the risks of infestation:

-- Plant early so corn is more mature should infected leafhoppers arrive.

-- Consider insecticidal seed treatments that can provide protection.

-- Consider foliar insecticides if corn leafhoppers are present before the V8 growth stage.

-- As the season progresses, remove volunteer corn plants that may serve as a green bridge for the corn leafhopper and as a reservoir for the corn stunt pathogens.

Scouting cornfields at least once a week is crucial to detecting corn leafhoppers. If no action is taken until honeydew or black sooty mold is visible, it's probably too late, Valmorbida added.

"Scout with a sweep net or a battery-powered hand vacuum," he suggested. "You can also place yellow sticky traps, the same ones used for corn rootworm, at field edges. They'll attract leafhoppers if they are present."

While infected corn leafhoppers have the potential to decimate corn yields, Kerns said it's important to keep things in perspective this early in the season.

"It's definitely something we want to watch, but at the same time, people shouldn't overreact," Kerns said. "Yes, it can be a serious pest, but I don't even know if we're going to get worrisome populations in my area, much less north of me. So, we do want people to be wary of them, but I just don't want people to panic."

University of Missouri Extension recently released a new publication to help farmers identify corn leafhoppers. It also provides scouting and management recommendations. Download it here: https://extension.missouri.edu/… .

Jason Jenkins can be reached at jason.jenkins@dtn.com

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