Johnston, IA (November 11, 2024) - Corn stunt disease, one of the most economically damaging diseases affecting corn across Latin America, has started appearing in the United States and may become more common, particularly in southern corn-growing regions.
The disease is caused by the bacterial pathogen corn stunt spiroplasma, which is transmitted from plant to plant by corn leafhoppers as they feed.
Corn stunt outbreaks in the U.S. have been linked to corn leafhopper populations migrating north from Mexico, where corn is continuously cultivated. The corn leafhoppers travel with prevailing winds and can cover long distances when aided by tropical storms.
Because temperature plays a significant role in corn leafhopper activity and reproduction, they tend to thrive in warm regions where corn is continuously available as a food source. Cold temperatures and the lack of secondary host crops have limited the spread of corn leafhoppers further north.
Early Indicators and Plant Impact
Corn stunt disease initially appears as small, chlorotic (yellow) stripes at the base of the leaves, which can gradually turn reddish-purple as the disease progresses. In severe cases, infected plants show reduced internode length, leading to stunted growth.
Plants may also develop multiple small ears with sparse kernel production, resulting in poor ear and kernel development. Affected ears often have a “loose tooth appearance” with poorly filled kernels and blank spots.
Management Practices
Managing corn stunt disease focuses on preventing infection by controlling the corn leafhopper population. A combination of cultural practices, early scouting and chemical controls can help.
“We hope for a nice, hard freeze this winter but that is out of our hands. For cultural controls, we recommend that farmers plant early. We have seen in our studies, that the later the [corn] leafhoppers move in and spread the disease, the less plant injury you’ll have,” said Brad Hopkins, product agronomist and entomologist for Corteva Agriscience. “Farmers should also be diligent in removing volunteer corn to disrupt [corn] leafhopper lifecycles.”
Insecticide applications may help reduce corn leafhopper populations. Foliar insecticides are often needed when corn leafhopper populations reach economic thresholds. Seed treatments can protect young plants but are effective only until the V3 growth stage.
In addition, farmers should avoid continuous corn planting to disrupt corn leafhopper breeding cycles. Controlling volunteer corn and narrow planting windows can also reduce host availability.
Southern corn growers should remain vigilant, especially as climate changes potentially favor the spread of disease.
If farmers think they have corn stunt in their fields in 2025, they are advised to reach out to their industry representative for support.
