OCCURRENCE OF THE ASIAN CITRUS PSYLLA AND ITS PARASITIC NATURAL ENEMIES IN THE RYUKYU ARCHIPELAGO, JAPAN

A survey of the seasonal occurrence of Asian citrus psylla, Diaphorina citri, which is the vector of Asian citrus greening disease, and of its parasitic natural enemies, was conducted at six sites containing Murraya paniculata on Ishigaki Island (24˚19'-36'N and 124˚4'-20'E, the southernmost part of the Ryukyu Archipelago), Okinawa, Japan. The population of adult psylla increased in early spring when newly sprouted shoots of M. paniculata were abundant, but the trends differed from place to place even on the same island. Two species of parasitic wasps were discovered. One was an unidentified encyrtid and another was the eulophid Tamarixia radiata. The populations of the encyrtid were rather stable and low, but populations of T. radiata fluctuated considerably.
A survey of parasitic natural enemies of Asian citrus psylla was also conducted in other areas of the Ryukyu Archipelago: Amami Island (28˚5'-30'N and 129˚0'-40'E, the northernmost area inhabited by Asian citrus psylla); Okinawa Island (26˚4'-53'N and 127˚37-128˚20'E); Kume Island (26˚17'-23'N and 126˚42'-50'E); Miyako Island (24˚42'-55'N and 125˚15'-29'E); and Yonaguni Island (24˚26'-28'N and 122˚56'-123˚3'E). On Amami Island, only the Asian citrus psylla was detected. On Okinawa, Miyako and Yonaguni Islands, the Asian citrus psylla and the same two parasitoids detected on Ishigaki Island were detected. On Kume Island, the Asian citrus psylla and the encyrtid parasitoids were found. T. radiata is an introduced natural enemy against Asian citrus psylla in Taiwan, and it is unlikely that this parasitoid occurs naturally in Japan.