Recent Outbreaks of the Maize Orange Leafhopper Cicadulina bipunctata Inducing Gall-like Structures on Maize in Japan

Summary

The maize orange leafhopper Cicadulina bipunctata is distributed widely from Africa to Asia including Japan, and northern Australia. Some cereals infested by C. bipunctata, such as maize and rice, exhibit stunted growth and severe swelling of leaf veins, symptoms commonly referred to as ‘wallaby ear disease’. Though previous studies attributed the symptoms to a leafhopper-transmitted virus, recent studies suggest that chemicals injected by C. bipunctata during feeding are important contributors to these symptoms. Therefore the damage is considered a sort of insect gall. Following the initiation of biyearly plantings of forage maize in Kyushu, Japan, C. bipunctata became recognized as a serious insect pest of forage maize. Since 2001 the total area of forage maize fields damaged by C. bipunctata has gradually increased, and outbreaks of C. bipunctata occurred in 2004. We speculate that relatively low winter mortality and early appearance of C. bipunctata are possible factors contributing to re-cent outbreaks. In central Kyushu, an increase of 1.3 generations per year following global warming is estimated for C. bipunctata by 2100, relative to 1990. Thus, C. bipunctata has the potential to become a serious insect pest of cereal crops other than forage maize in the future.