Transmission Efficiency of Rice Waika Virus by the Green Rice Leafhoppers, Nephotettix spp. (Hemiptera : Cicadellidae)

Vectors of the rice waika virus (RWV) was specific to the genus Nephotettix leafhoppers : N. cincticeps UHLER, N. virescens DISTANT, N. nigropictus STAL, and N. malayanus ISHIHARA et KAWASE. There was no essential difference in the rate of active transmitters among the nine local colonies of N. cincticeps over the west of Japan. The 1st-instar nymph was slightly less efficient in transmission than the mid- and late-instar nymphs. There was no difference in transmission efficiency between sexes and among adults up to 15 days old but a slight decrease in efficiency in adults 20 days after emergence. Mid- and late-instar nymphs and adults transmitted the RWV with equal efficiency. Transmission efficiency increased proportionally with an increase in acquisition feeding periods. The retention period in the insects decreased rapidly within a few days after termination of the acquisition feed. The leafhoppers transmitted the RWV in a semipersistent manner, and could be arranged comparatively in a descending order of transmission efficiency as follows : N. virescens≥N. malayanus > N. cincticeps > N. nigropictus. However, N. cincticeps is one of the most important vectors of RWV because of its predominance in the disease epidemic area.