COLUMBIA, Mo. — University of Missouri Extension is encouraging corn producers to closely monitor fields after corn leafhoppers were confirmed in five Missouri counties earlier this growing season.
Extension entomologist Ivair Valmorbida said the insect has now been identified in Boone, Barton, Christian, Cooper and Lawrence counties. The first detections were made in mid June, with additional confirmations through early July. According to MU Extension, the pest appeared about three weeks earlier this year than it did in 2025.
While the insect itself feeds on corn, the greater concern is its ability to transmit corn stunt pathogens that can significantly reduce yields.
Research has shown corn is most vulnerable to infection from emergence through the tasseling stage. Although infection can occur later in the season, the greatest yield losses are typically seen when plants become infected before the R1 growth stage.
The corn leafhopper reproduces only on corn but has also been observed on grasses such as Johnsongrass and gamagrass, along with alfalfa, triticale and certain winter annual weeds. Those plants are not believed to serve as feeding hosts.
Adult corn leafhoppers are about one eighth inch long with yellow to tan coloring. They can be identified by two small black spots between the eyes surrounded by lighter colored halos and generally lack the additional dark markings seen on other leafhopper species. The insects are commonly found inside the corn whorl or on the underside of leaves.
As they feed, corn leafhoppers leave behind a honeydew like residue that can promote black sooty mold.
Corn stunt symptoms may develop anywhere from one to eight weeks after infection. Signs include yellow streaking near the base of leaves, yellowing or reddening of leaf tips, shortened stalk internodes, poorly filled ears, malformed kernels and, in severe cases, plant death.
Valmorbida said it is not yet known whether the Missouri leafhoppers are carrying corn stunt pathogens, but growers should treat every detection as a potential risk.
“Growers should assume that any corn leafhopper has the potential to be infectious.”
Because there is no cure once plants become infected, Valmorbida said management should focus on early scouting and reducing insect populations before the crop reaches the reproductive stage.
“At this time of the year, scout efforts should focus on late planted corn. If present, an insecticide application may be warranted if corn has not reached the R1 growth stage.”
MU Extension encourages producers to monitor fields regularly, especially later planted corn, where the crop remains most vulnerable to infection.
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