Also known as:
English:Corn Stunt Leafhoppers, Corn Leafhopper, Maize Leafhopper
Spanish: Chicharrita del Maíz, Cicadula Amarillenta, Cigarrita del Maíz, Parramirento Maiz, Salta Hoja del Maíz, Saltahojas.

Latin names: Dalbulus maidis, D. elimatus and other less common Dalbulus species.

Life cycle and description

• Egg stage: Tiny, oval-shaped eggs with little color when immature. The eggs are less than 1 mm in length and 0.2 mm wide. A few days after oviposit the eggs develop a tuft of diagnostic microfilaments from the proximal end of the egg, which can be seen with a 10x hand lens. At 7-10 days the eggs became easier to see as they become white and have red eyespots. Eggs are typically deposited on mid-veins of leaves of young maize plants generally in the whorl. Several eggs will occasionally be oviposited in a row. Egg stage lasts 9-12 days in summer but several weeks in cooler weather.
• Nymph stage: There are five translucent, yellow nymph instars. Development time for nymphal instars can take from 2.5 days at 27°C to 33 days at 10°C. The first instars are pale yellow with back eyes. They are less than 1mm long. From the second instar through to the fifth instar, they have a pair of irregular, black spots on the interior margin of the last two abdominal tergites. The last instar is a little less than 4 mm long. During this instar, the mesothoracic and metathoracic wing buds extend posteriorly over the abdomen. The nymphs feed at the base of the leaves in the whorl and/or between the leaf bases on the lower stem.
• Adult stage:The adults are light yellow with uneven, black spots on the abdomen. The spots are larger and more numerous on leafhoppers in high altitudes and cool climates. Two large spots are located on the head over the ocelli, which are greater in diameter than the ocelli. At times there may be several other dark spots on the head. Adults range in length from 3.7-4.3 mm. Adults lifespan ranges from 45 to almost 180 days, depending on temperature. Lower temperatures favor longevity. During a lifetime adult females can lay over 600 eggs. Number of eggs deposited at one time range from 3 to 14. Adults secrete honeydew during feeding which is occasionally fed on by ants.
• Total life cycle time is approximately 25-30 days at optimum temperature of 25°C.
• Adults overwinter in grassy vegetation, typically along waterways, fence lines and in ditches.
• There is usually a minimum of two generations of corn leafhopper on each maize crop.
• Regions at high altitudes and with short rainy seasons have fewer generations compared to regions with long rainy seasons and overlapping crops.

Confirmation

The adult leafhopper is easily observed in the maize seedling’s whorl, particularly in the early morning when they are less active. D. maidis is can be correctly distinguished from other Dalbulus species by the amount and size of spots of its head (a 10x hand lens may be needed) as well as by examining the shape of the male’s aedeagus.

Why and where it occurs

Dispersal can be local and also widespread. Leafhoppers are sometimes carried great distances by tropical storms.

Host range

Maize

Geographical distribution

The corn leafhopper is generally found in maize growing regions in the neotropics at all altitudes. In Peru for example, this pest can be found from sea level to 3200m above sea level. D. maidis is also reported from the southern USA, Mexico, Central and South America and the Caribbean.

Damage

• Mechanism of damage: Corn leafhoppers in the adult and nymph stage feed on maize plants by sucking leaf juices which can result in withering of leaves and chlorosis. Adult leafhoppers produce honeydew which is deposited on leaf surfaces and can result in black sooty mould which reduces photosynthetic capacity of leaves. Corn leafhoppers are most damaging due to their role as vectors of Spiroplasma kunkelii (syn. Corn Stunt Spiroplasma) that causes corn stunt, a major constraint to maize in the New World. Once a corn leafhopper has acquired S. kunkelii through feeding it will continue to transmit it for life. Corn leafhoppers are also known to transmit maize rayado fino virus, maize dwarf mosaic virus, maize stripe virus, maize mosaic virus, and maize bushy stunt phytoplasma.
• When damage is important:If the corn stunt leafhopper transmits diseases to the maize plant, particularly maize planted late, yield loss could be severe.
• Economic damage: In irrigated fields with continuous maize cropping, severe corn leafhopper infestation can occur with subsequent pathogen transmission causing significant yield loss.

Symptoms of corn stunt include chlorosis of leaf margins, chlorotic streaks, and purpling of leaves. At low temperature, chlorosis and purpling may be restricted to the base of upper leaves. Foliar symptoms appear close to tasseling. Infected plants are stunted due to shortening of internodes and numerous, barren ear shoots develop. Often plants tiller, cob and root excessively and tassels are sterile. Plants can be completely barren or suffer from poor seed set and reduced cob size. Under severe infection, plants can die prematurely.

• Newly introduced maize varieties with low levels of resistance are most susceptible to corn stunt.
• Disease damage seems to be most serious when the plants are infected at the seedling stage; however, damage can still be severe when infection takes place at the 16-leaf stage.
• Symptoms of the corn stunt disease S. kunkelii develop three weeks after the maize plant is infected.

Management principles

Monitoring

• Monitoring for leafhopper incidence during the first two months of crop growth is particularly important.

Control

• Avoiding continuous maize monoculture and managing volunteer maize plants during the off-season will help reduce leafhopper and corn stunt incidence.
• Removing plants (roguing) infected with corn stunt early in the season can reduce disease spread.
• Local maize varieties are often more resistant to corn stunt than introduced varieties. Local varieties from Nicaragua and other regions of Latin America have shown good resistance to corn stunt.
• Yellow maize varieties are often more resistant.
• Several Hymenoptera species are natural enemies of leafhopper nymphs, adults and eggs. Other natural control agents reported in Mexico and Puerto Rico include the larval parasitoids Gonatopus bicolor and a species of Strepsiptera.
• A somewhat expensive control method for sweet corn crops is the use of reflective mulch. This repels the adult corn leafhopper.
• Insecticides can reduce the incidence of leafhoppers. The systemic insecticide oxydemeton-methyl and the contact insecticide carbaryl have been successfully used against leafhopper. However, insecticide is often regarded as economically unviable.

References

CAB International. 2002. Crop Protection Compendium. Wallingford, UK: CAB International.

Collar, C., C. Frate and  C. Summers. 2003. Corn Stunt Disease- A Costly Problem for Growers and Dairymen. University of California. http://ucce.ucdavis.edu/files/filelibrary/1214/5465.pdf (2 February 2007).

Godfrey, L.D., S.D. Wright, C.G. Summers and C.A.  Frate. 2006. UC IPM Pest Management Guidelines: Corn. University of California. http://www.ipm.ucdavis.edu/PMG/r113301111.html (2 January 2007).

King, A.B. and J.L. Saunders. 1984. The Invertebrate Pests of Annual Food Crops in Central America. London, UK: Overseas Development Admin.

Ortega A. 1987. Insect pests of Maize: A Guide for Field Identification. Mexico, D.F.: CIMMYT.

Nuessly, G., K. Pernezny, P. Stansly, R. Sprenkel and R. Lentini. 2006. Corn Leafhopper: Dalbulus maidis. University of Florida. http://fciig.ifas.ufl.edu/frleadm.htm (2 January 2007).

Tsai, J.H. 1987. Bionomics of Dalbulus maidis (DeLong and Wolcott). A vector of mollicutes and virus (Homoptera: Cicadellidae). In K. Maramorosch and S.P. Raychaudhuri (eds.), Mycoplasma diseases of crops: basic and applied aspects. New York: Springer-Verlag. Pp. 209-221.

Contributors: Gabrielle Turner, David Bergvinson, and Biswanath Das