Abstract
Bemisia tabaci Q-biotype is one of the most important agricultural pests worldwide. The distribution range of the Q-biotype has expanded throughout the main islands of Japan since soon after the first detection in 2004 and has replaced the formerly dominant B. tabaci B-biotype in some areas. However, such a replacement has not been observed in the southwestern islands of Japan （Ryukyu Islands）. Until 2009, Q-biotype had been found only in a few greenhouses of bell peppers on the southern part of Okinawa Island. To determine the current range expansion status of Q-biotype in the Ryukyu Islands, we investigated the occurrence of Q-biotype throughout the area （218 sampling sites on 10 islands） from 2009 to 2011. The distribution range of Q-biotype has expanded within Okinawa Island but was not found on most of the remaining islands. The occurrence of Q-biotype on Okinawa Island was clearly predominant in bell pepper greenhouses: Q-biotype was detected in 84% of the bell pepper greenhouses investigated （number of detection sites/number of sampling sites）whereas the frequency from other host plants was less than 23%. This phenomenon has not been reported in other areas, and the cause should be clarified.
