First detection of corn leafhopper in Minnesota in 2024

Yucheng Wang, Research Associate, Department of Entomology, and Fei Yang, Extension entomologist

Figure 1. Corn leafhopper adult. It can be differentiated
from other leafhoppers by the presence of two black spots
 located between their eyes. (Photo courtesy of Danielle
 Sekula from Texas A&M AgriLife Extension).

The corn leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) (Figure 1), is an invasive insect native to Mexico that has spread extensively across the Americas, covering tropical regions of North, Central, and South America. First detected in the United States in the 1940s, it has since expanded into southern states, including California, New Mexico, Texas, Arkansas, Louisiana, Mississippi, and Florida, where sporadic outbreaks have caused economic losses. By 1981, the insect was documented as far north as Ohio. In 2024, Texas A&M AgriLife Extension issued an alert about a surge of corn leafhoppers in the Texas Mid-Coast region. Previously, the most recent report of this insect was in the lower Rio Grande Valley of Texas in 2016. During the 2024 growing season, the corn leafhopper spread widely throughout Texas, Oklahoma, eastern New Mexico, Kansas, Missouri, and Arkansas, with late-season detections in Illinois, Indiana, Nebraska, and Wisconsin. In September 2024, corn leafhopper was identified for the first time in Minnesota, with significant infestations of adults and nymphs on V4-V5 stage corn plants in a trial plot on the St. Paul campus of the University of Minnesota (Figure 2).

Figure 2. Corn leafhopper infestation in corn plot located on the St. Paul campus of the University of Minnesota in 2024. (Photo courtesy of Fei Yang, UMN Dept. of Entomology).

The corn leafhopper is a specialist herbivore that has coevolved with plants of the Zea genus, feeding primarily on corn (Zea mays L.) and its wild relatives, the teosintes (Zea spp.). Females prefer healthy corn plants over those previously infested by conspecifics. Its high reproductive potential and ability to migrate over long distances contribute significantly to its capacity to infest multiple fields. While corn is its primary host, the leafhopper can also utilize alternative hosts, such as gamma grasses. During the off-season, corn leafhoppers can temporarily survive by feeding on other plants, including sorghum seedlings, Johnsongrass, signalgrass, millet, alfalfa, winter wheat, and triticale. Additionally, it may endure in moist soils with minimal plant material, using these environments as temporary refuges until favorable conditions return.

Life cycle  

The corn leafhopper’s life cycle is directly influenced by temperature and humidity. In areas with higher elevations or short rainy seasons, the leafhopper completes at least two generations per corn crop. In regions with longer rainy seasons or overlapping crops, multiple generations can occur. In areas where corn is continuously grown with irrigation, corn leafhopper maintains breeding populations year-round, causing significant economic damage. Conversely, in regions with distinct dry seasons and no irrigated corn, adult leafhoppers migrate after the crop matures, likely overwintering in as-yet-undiscovered habitats. Even without hosts, adults can survive for several weeks under late-season conditions, as long as moisture or an alternative dry-season food source is available. When corn is planted at the start of the rainy season, migrating adults typically infest the whorls of young seedlings, feeding and laying eggs. Their activity is often synchronized with spring rains, which act as a trigger for migration and reproduction.

The optimal temperature range for corn leafhoppers is 25-30°C, with a generation time of approximately 25-30 days at 25°C. Eggs typically hatch on the abaxial side of leaves within 9-12 days, and the nymphs go through five developmental stages over about 17 days. Adult females, generally larger and heavier than males, begin laying eggs 1-2 days after emergence, depositing 400-600 eggs over their lifetime. The average adult lifespan is 7-8 weeks at 26°C, with some individuals can survive up to 15 weeks.

The corn leafhopper damages corn by piercing plant tissue to extract phloem sap, injecting toxic spittle, and primarily transmitting disease-causing pathogens. It serves as a vector for four major stunting pathogens: two mollicutes, corn stunt spiroplasma (CSS) and maize bushy stunt phytoplasma (MBSP), and two viruses, maize rayado fino virus (MRFV) and maize striate mosaic virus (MSMV). Heavy infestations of corn leafhoppers can lead to leaf desication from intense sap extraction, causing browning and premature drying. Additionally, honeydew excretion promotes sooty mold, inhibiting photosynthesis and limiting sugar and carbohydrate production essential for grain fill. The combination of direct feeding and indirect pathogen transmission can cause significant reductions in corn productivity and quality, with as few as ten insects capable of harming 10-day-old seedlings.

Identification

Morphology

Corn leafhopper females use their ovipositor to insert eggs into the leaf, often along the midvein. Multiple eggs may be laid in a row, commonly in the whorls of corn seedlings. The eggs are small, about 1.3 mm long, and initially nearly colorless with a transparent chorion. After 7-10 days, they turn white and develop red eye spots. Shortly after being laid, a tuft of diagnostic microfilaments protrudes from the proximal end of the egg. The nymphs are pale yellow with black eyes. From the second to fifth instars, a pair of irregular black spots appear on the anterior margin of the last two abdominal tergites. In the fifth instar, the mesothoracic and metathoracic wing buds extend posteriorly over the abdomen. Adults measure a few millimeters in length, ranging from 3.7 to 4.3 mm, and can be found on both the abaxial and adaxial sides of the leaves. They typically have a light color, varying from yellow to white, with variable black spots on the abdomen. A key identifying feature is two large spots on the head over the ocelli, each more than twice the diameter of the ocelli (Figure 1). Additionally, their posterior tibiae have two rows of spines. Adult corn leafhoppers are often observed infesting the whorls of seedling corn plants as well as in older plants when the whorl can be readily observed from above. They are easier to detect during early morning hours when they are less active, making plant inspections during this time ideal.

Symptoms of stunting diseases on corn

CSS, caused by Spiroplasma kunkelii, results in broad yellow streaks on the leaves, along with stunting and distinct reddening of foliage. MBSP, a phytoplasma infection, is present with leaf reddening, internode shortening, stunting, reduced grain yield, and suppression of lateral shoots. Unlike CSS, MBSP does not cause yellow streaks, and symptoms in later infections are difficult to distinguish from CSS infection. MRFV causes small chlorotic spots along leaf veins that elongate and spread over time, while MSMV is marked by mild chlorotic streaks, mottling, and reduced plant height. Identifying stunting pathogens by symptomatology is difficult, as symptoms often overlap among these pathogens, and coinfections can mask specific disease indicators. Symptom expression is further influenced by the plant’s genetic traits, such as anthocyanin production (pigments associated with sugar metabolism, giving plants a purple or reddish hue), and environmental conditions. While leaf reddening is a common sign of stunting disease, some plants only exhibit chlorosis along the leaf margins and tips (Figure 3). Consequently, laboratory analysis is crucial for accurately identifying and diagnosing stunt diseases.

Figure 3. Possible symptomology attributed to red stunt disease in Minnesota in 2024 (left) Broad yellow streaks and small chlorotic spots on leaves; (right) Red stunt disease in the ear leaf.

Insecticidal management

Seed treatments have proven particularly effective in controlling corn leafhoppers, even outperforming spray applications. Neonicotinoid-based products, such as imidacloprid, clothianidin, and thiamethoxam, are commonly registered and used in Brazil for control of corn leafhoppers. Combining seed treatments during the early crop stages with targeted insecticide applications maximizes control reliability. Sprays are typically applied once corn leafhoppers are detected in the corn fields to limit vector populations and disease spread. Commonly used insecticides include acephate, methomyl, thiamethoxam, and imidacloprid combined with β-cyfluthrin. U.S. southern entomologists recommend applying targeted insecticides early, before significant damage or disease transmission occurs, to maximize efficacy. For optimal control, apply Sivanto® Prime at 7 fluid ounces per acre, which provides about 80% control within three days, with further improvements by day seven. Pyrethroids, such as lambda-cyhalothrin (5.12 fluid ounces per acre) and bifenthrin (6.4 fluid ounces per acre), can offer over 90% control. Dimethoate at 1 pint per acre maintains 70–80% effectiveness over 14 days.

References

Biles, S. 2024. Leafhoppers in corn: Update. Texas A&M AgriLife Extension, Mid-Coast IPM. https://agrilife.org/mid-coast-ipm/leafhoppers-in-corn-update/

Corn leafhopper: Dalbulus maidis, Cicadellidae. University of Florida, Florida Corn Insect Identification Guide. https://erec.ifas.ufl.edu/fciig/frleadm.htm

Henrique, P., Glauber, R. S., Jonas, A. A. 2022. Corn stunt pathosystem and its leafhopper vector in Brazil. J. Econ. Entomol. 115(6), 1817–1833, https://doi.org/10.1093/jee/toac147

Kerns, D., Führ, F. M., Biles, S., Sekula, D., Santiago-González, J. C., Wilson, G., Mays, T., Drake, D., Isakeit, T., Alabi, O. 2024. Corn leafhopper and the red stunt disease complex. Texas A&M AgriLife Extension, Mid-Coast IPM. https://agrilifeextension.tamu.edu/asset-external/corn-leafhopper-and-the-red-stunt-disease-complex/

Nault, L.R. 1990. Evolution of an insect pest: maize and the corn leafhopper, a case study. Maydica 35: 165–175.

Oliveira, C. M., Lopes, J. R. S., Nault, L. R. 2013. Survival strategies of Dalbulus maidis during maize off-season in Brazil. Entomologia Exp. Applicata. 147(2): 141–153.

Poletto, T. B. 2024. Enhancing Dalbulus maidis (Hemiptera: Cicadellidae) control: an integrated approach combining Cordyceps javanica (Ascomycota: Hypocreales) and insecticides. Master’s thesis, Universidade de São Paulo.