Corn Stunt Pathogens

Corn stunt is a re-emerging threat to corn production in the U.S., with outbreaks reported in several states during the 2024 growing season. In the U.S., the disease is caused by a complex of plant pathogens that may infect plants individually or in combination. These include two bacterial pathogens, the corn stunt spiroplasma (Spiroplasma kunkelii) and maize bushy stunt phytoplasma (Candidatus Phytoplasma asteris, 16SrI-B subgroup), as well as the maize rayado fino virus (MRFV). All three pathogens are transmitted by the corn leafhopper (Dalbulus maidis), an insect vector whose geographic range has expanded in recent years.

Infected corn plants typically display chlorosis or reddening of the leaf tips, followed by shortened internodes, resulting in plant stunting. Other common symptoms include tillering, production of multiple ears with few kernels, male flower sterility, and small or deformed ears. Due to the diversity and overlap of symptoms caused by these pathogens and that these symptoms not exclusive to corn stunt disease,  laboratory-based diagnostic methods, such as polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay (ELISA), are required to confirm the presence of disease.

Unfortunately, there are no curative measures available for this disease. As a result, management efforts focus on monitoring the presence of the insect vector in corn fields rather than applying economic thresholds. The current distribution of corn leafhopper in the U.S. can be viewed on the following map: Corn Leafhopper Map.