Seasonal abundance of Maiestas banda (Hemiptera: Cicadellidae), a vector of phytoplasma, and other leafhoppers and planthoppers (Hemiptera: Delphacidae) associated with Napier grass (Pennisetum purpureum) in Kenya

摘要

Napier grass (Pennisetum purpureum Schumach), the main fodder crop in eastern Africa, has recently been severely affected by Napier stunt disease, which is caused by phytoplasma. We have recently confirmed that a leafhopper, Maiestas banda (Kramer) transmits phytoplasma in Napier grass in Kenya. Several other species of leafhoppers (Cicadellidae) and planthoppers (Delphacidae) are also associated with Napier grass, and some could be potential vector(s) of phytoplasma, but little is known about phenology and movement activity of these insect groups. We monitored the populations of M. banda and other leafhoppers and planthoppers in Napier grass fields at two sites in western Kenya for 18 months. High population densities were observed for M. banda, suggesting that it plays a major role in the disease epidemics in the region. Sampling with Malaise traps and a vacuum-suction sampler revealed that M. banda and five other species (Cicadulina mbila (Naudé), Cofana polaris Young, Cofana unimaculata (Signoret), Leptodelphax dymas Fennah, Maiestas sp.) exhibited a high proportion of males in the trap catches, implying higher mobility in males than females. A suction sampler collected more individuals of three species (M. banda, Maiestas sp., and Thriambus strenuus Van Stalle) from phytoplasma-infected than healthy plants at both sites. The populations of M. banda and other five species (C. unimaculata, Maiestas sp., L. dymas, T. strenuus, and Rhinotettix sp. 1) showed a conspicuous peak at the end of the short rainy season (Sep to Dec), implying that common regulatory factors such as rainfall may affect the leafhopper and planthopper complex.