Nobuyuki Endo

Interspecific Pheromone Cross-Attraction Among Soybean Bugs (Heteroptera): Does Piezodorus hybneri (Pentatomidae) Utilize the Pheromone of Riptortus clavatus (Alydidae) as a Kairomone?

The chemical and ecological function of cross-attraction of Piezodorus hybneri (Pentatomidae) to the Riptortus clavatus (Alydidae) pheromone (a mixture of three components) was studied. In a field attraction test using traps with synthetic pheromone components, P. hybneri was attracted to (E)-2-hexenyl (E)-2-hexenoate, a component of the R. clavatus pheromone. Other components had neither an additive nor a synergistic effect on the attraction of P. hybneri. Neither (E)-2-hexenyl (E)-2-hexenoate nor other components of the R. clavatus pheromone were detected in volatiles or whole-body extracts of P. hybneri adults by gas chromatographic analysis. In addition, (E)-2-hexenyl (E)-2-hexenoate could not be found in volatiles of soybean plants. Therefore, it appears that P. hybneri responds to a component of the R. clavatus pheromone that is not emitted by P. hybneri itself. We discuss this interspecific pheromone cross-attraction of the soybean bug and hypothesize that P. hybneri utilizes the pheromone of its competitor as a kairomone for host location.

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

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.