Bemisia tabaci (Gennadius) is considered to be the most economically important pest insect worldwide. The invasive variant, the Q biotype of B. tabaci was first identified in 2004, and has caused significant crop yield losses in Japan. The distribution and molecular characterization of the different biotypes of B. tabaci in Japan have been little investigated. In this study, B. tabaci populations were sampled from the Japanese Archipelago, the Amami Archipelago and the Ryukyu Islands between 2004 and 2008, and the nucleotide sequences of their mitochondrial cytochrome oxidase I genes were determined. Bayesian phylogenetic relationship analysis provided the first molecular evidence that the indigenous Japanese populations could be separated into four distinct genetic groups. One major native population from the Japanese Archipelago, given the genetic group name Lonicera japonica, was separated into an independent group, distinct from the other genetic groups. The second major population, the Nauru biotype in the Asia II genetic group, was identified in the Amami Archipelago and the Ryukyu Islands. Two distinct minor genetic groups, the Asia I and the China, were also identified. One invasive B‐related population belonging to the Mediterranean/Asia Minor/Africa genetic group has been identified in Honshu. All lineages generated by the phylogenetic analyses were supported by high posterior probabilities. These distinct indigenous B. tabaci populations developed in Japan under geographical and/or biological isolation, prior to recent invasions of the B and Q biotypes.

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On the main islands of Japan and in Taiwan, the spider mites Tetranychus kanzawai and T. urticae (green and red forms) are major pests on vegetable crops. The present study revealed that the dominant spider mite species injurious to vegetables in Okinawa, located between the main islands of Japan and Taiwan, differed from those in the two regions, providing important and fundamental information for controlling spider mites in Okinawa. T. okinawanus was the most dominant species throughout Okinawa with the broadest host range, even though the species has been regarded as a non-pest to date. T. piercei, which has similarly not been treated as a vegetable pest, was the second most dominant species with respect to frequency of occurrence and host range. T. kanzawai and T. urticae (green form) were comparable in the frequency of occurrence to T. piercei in the northern part of Okinawa (Okinawa Islands), whereas they were scarce in the southern part (Sakishima Islands). As other less-dominant species, T. ludeni, T. neocaledonicus and T. pueraricola were found infesting several vegetable crops. T. urticae (red form) was not found in this study.

The absolute population density and natural mean dispersal distance of the sugarcane click beetle Melanotus sakishimensis Ohira (Coleoptera: Elateridae) were estimated by using mark-recapture experiments in an agricultural area

The species composition of spider mites on crops in Okinawa is peculiar in that Tetranychus okinawanus and T. piercei are dominant on most islands, whereas T. urticae (green form) and T. kanzawai are not. To determine the source plants of Tetranychus species infesting crops, as well as to contribute to our understanding of the cause of this peculiar mite fauna, we collected Tetranychus mites on non-crop plants throughout Okinawa (more than 450 sites on 15 islands) and identified them. Except in the case of T. parakanzawai, the species frequently found on crops tended to occur frequently on non-crop plants, suggesting that the peculiar species composition on crops reflects that also on non-crop plants. T. parakanzawai has been rarely found on crops but frequently found on particular non-crop plants, possibly due to the narrower host range of this species. The type of host plants varied among mite species; for example, T. okinawanus was frequently found on indigenous plants inhabiting the seashore and invasive weeds, T. piercei and T. parakanzawai on inland indigenous plants, T. urticae (green form) on invasive weeds, and T. neocaledonicus on introduced trees. These results are of great significance when considering vegetation control as a tactic for the integrated management of spider mites.