Small insects that damage corn crops are being reported in Oklahoma and Missouri fields for the first time this year.
Corn leafhoppers are small, tan torpedo-shaped bugs about one-eighth of an inch long. They latch on to the underside of the plant leaves and in other shaded areas of corn.
The pest can feed on corn plants, and carries three types of pathogens that can cause corn stunt disease – which leads to deformed grain, loose or absent kernels or a reduction of the plant’s size, according to a University of Missouri Extension Service news release.
At least one case of corn stunt disease has been confirmed in southwest Missouri, with several cases of the disease’s symptoms reported in that part of the state. In Oklahoma, corn leafhoppers and the pathogens linked to corn stunt have been confirmed in a central Oklahoma county, and symptoms of the disease have been seen across the state.
The insects are typically present farther south, from the southern U.S. to South America. But warmer temperatures allowed corn leafhoppers to expand their habitat range farther into the United States, experts said.
While researchers in Missouri and Oklahoma weren’t expecting to see corn leafhoppers, it makes sense that the bugs appeared, said Ashleigh Faris, cropping system entomologist for the Oklahoma State University Extension and Oklahoma’s integrated pest coordinator.
“It's not a surprise to see that the insect would come up to where the host is, especially if it's at a climate that is amenable to the host,” Faris said.
With harvest time approaching, experts in these states said there’s little to be done. They’re working to learn more about the impact and how to better prepare.
Difficult to spot
In Texas, there was a corn leafhopper flare up south of the Rio Grande Valley in 2016. Now the bug is back – and spreading a lot, said David Kerns, Texas A&M AgriLife Extension Service specialist and associate head for the university’s entomology department.
Kerns said this year Texas researchers and producers were not looking for leafhoppers earlier in the season, but by May the signs of corn stunt in the Rio Grande Valley were evident. Most of the corn was far enough along, so it did not raise a lot of concern, he said.
“People don't notice it until it's like, bad, because in general, corn doesn't get scouted like cotton and some of the other crops as extensively,” Kerns said. “And so it just got overlooked.”
There is a lag between when the bug infects the plant with pathogens and when the plant actually shows symptoms, said Faris. It takes about a month for plants to show signs of corn stunt.
“So the thing is, you may be looking at your crop and saying, ‘You know what, everything looks good,’ and then gradually you might start to actually see some symptoms that could be concerning,” Faris said.
It can also be difficult to distinguish if crops have corn stunt disease, or the symptoms are due to other pressures such as environmental factors, Faris said.
The insect’s impact
It is too soon to tell what the corn leafhoppers' impact will be on yields, said Ivair Valmorbida, University of Missouri entomology professor and extension specialist. The damage to plants varies, he said.
“Some of the plants were dying, others, just like mild symptoms,” Valmorbida said. “It depends. It all depends.”
The pest has not caused large losses in the U.S., but it has in other places – such as Argentina and Brazil, which have seen an increase in the insect’s numbers in recent years, according to the Texas A&M Agrilife Extension.
Kerns said while the bug should be closely watched, he does not think Texas should be worried because conditions in South America are different than North America.
This year in central Texas, Kerns said corn leafhoppers impacted corn that was planted later. In one field, he harvested some corn from diseased plants and healthy plants by hand.
“We had a 66% reduction in yield on the diseased plants versus what looked like healthy plants,” Kerns said. “Probably in that particular field, here’s probably 10% of the ears affected.”
Managing damage
The management for the pest and disease depends on the insect’s path and when they show up in fields, Valmorbida said. Because corn is close to harvest time in Missouri, there is not a rescue treatment for infected plants this season, he said.
With the emergence of this pest, Valmorbida said people may need to go out and scout their cornfields earlier in the season to capture the insects. Then, producers can work to manage the insect before the disease hits.
“So that will be a change in the way that we're going to see corn fields, I believe,” Valmorbida said.
The bug does not survive freezes in the winters, but adult corn leafhoppers can survive over winter in grasses like wheat if the weather conditions are right. For Faris, it's important to lead with caution because there is a lot to learn about the pest and its impact.
Extension experts said producers can reach out to their extension service if they have questions.
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.
