Performance and Behaviour of the Leafhopper (Maiestas banda; Homoptera: Cicadellidae) Vector of the Napier Stunt Disease on Napier Grass (Pennisetum purpureum)

Napier grass remains an important strategic grass species in east African mixed crop-livestock systems. However, production of several varieties of the grass remains constrained by phytoplasmic disease, Napier stunt disease (NSD), which is transmitted by the leafhopper, Maiestas banda. For smallholder farmers of western Kenya who rely on the grass for livestock feed and pest control in push-pull farming systems, effective control strategies of the disease and the vector remain elusive. With a view to understanding potential host plant resistance mechanisms against the leafhopper, I investigated growth, development and behaviour of the leafhopper on a variety of host plants: Pearl millet and five Napier grass varieties; susceptible Bana, resistant Kitale A, Kitale B, South Africa and Ouma 2. To determine performance and behaviour of M. banda on susceptible and resistant varieties, the following experiments were conducted: a) host selection and preference in a choice test using i) live plants and ii) plant volatile organic compounds (VOCs) collected using head space sampling. b) determination of feeding through honeydew excretion c) population development. On host selection based on volatiles and choice tests between Bana and the other varieties there was no preferential selection by M. banda to settle or go for susceptible Bana than the resistant varieties. There were no significant differences in honeydew excreted between susceptible and resistant Napier variety-fed insects. Significant differences in honeydew excretion were only found between Bana and pearl millet, both susceptible to the pathogen. Population development was not different between the insects raised on Bana and those raised on Kitale A, B, South Africa and Ouma 2. However, insect numbers were significantly higher on pearl millet. This study therefore did not show any significant differences in performance and behaviour of M. banda on resistant and susceptible varieties when the three insect behaviour attributes were studied.