Fallopia japonica（Japanese knotweed, Polygonaceae）, native to Japan, has been a serious invasive perennial weed in North America and large parts of Europe, especially in the UK, where there is an urgent need for a classical biological control strategy. Surveys have confirmed the presence of specialized plant pathogens in the native range of Japan. The results of the surveys showed that three fungal diseases of two rusts and a leaf-spot disease were predominantly common and widespread in the field. These rusts were identified as Puccinia polygoni-amphibii var. tovariae and Aecidium polygoni-cuspidati. Furthermore, a leaf-spot fungus morphologically identified as Mycosphaerella polygoni-cuspidati is also distributed widely in Japan. In the field, P. polygoni-amphibii var. tovariae and M. polygonicuspidati were confirmed to have severe infectivity to F. japonica. Thus, it is suggested that these two pathogens have high potential to become classical biological control agents for F. japonica.
Fallopia japonica, originating from Japan, is a problematic invasive weed in both North America and Europe, especially in the UK. Our results indicate that a coevolved rust pathogen, Puccinia polygoni-amphibii var. tovariae has the potential to be a classical biological control agent for F. japonica. In this study, in order to find fungal endophytes that increase the pathogenic aggressiveness of P. polygoni-amphibii var. tovariae, we observed the development of rust disease in the field to determine uninfected and infected periods, and isolated them from the leaves of F. japonica in these periods. A total of 465 endophytic fungi were isolated from F. japonica in May and September of 2005 and 2006, which were uninfected and infected periods with the rust, respectively, and they were classified into 15 taxa. Two genera, Colletotrichum and Alternaria, were predominant as endophytes in F. japonica. Five genera were recovered from F. japonica only in September. Of these genera, one Phyllosticta isolate increased the virulence of P. polygoni-amphibii var. tovariae, following pre-inoculation with the endophyte ahead of the pathogen. Thus, it is suggested that the Phyllosticta would be a synergist of the rust disease, thereby increasing its potential as a biological control agent of F. japonica.
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.
Amblyseius swirskii（Acari: Phytoseiidae） has been reported to be an effective biological control agent against Thrips palmi. Three release methods of A. swirskii were investigated for suitability with lateral branch taking-down cultivation, sprinkle release method: sprinkling A. swirskii onto leaves （the conventional method）; broadcast release method: release from the top of the plant; and paper cup release method: release using a paper cup containing A. swirskii, its food and oviposition substrate. A. swirskii dispersed rapidly on the main branch by the broadcast release method. In contrast, on the lateral branch, which is the main harvest branch for cucumber fruits, A. swirskii dispersion was slower after release by the broadcast release method than by the paper cup release method. The sprinkle release method resulted in poor dispersion, because many A. swirskii remained on the leaf which they were released. The paper cup release method reduced the effect of Beauveria bassiana ES which was applied for control of T. palmi adult which A. swirskii does not prey on. Therefore, we conclude that paper cup release is the method most suitable for lateral branch taking-down cultivation of cucumber and should be performed in combination with broadcast release for stable control of Thrips palmi.