The mile-a-minute weed, Persicaria perfoliata (L.) H. Gross (Polygonaceae), was first established in the United States in Pennsylvania and Maryland in the 1930s (Wu et al. 2002), and has been placed on noxious weed lists in several states of the United States because of the damage it causes in infested orchards, nurseries, and horticultural crops (Oliver & Coile 1994; Wu et al. 2002). Because of its rapid growth, the weed readily invades forests or forest edges (Wu et al. 2002). In addition, the weed’s thorny vines impede movement of wildlife and interfere with human activities (Okay 1997). By 2003, the plant was found in 8 states (Delaware, Maryland, New York, Ohio, Pennsylvania, Virginia, West Virginia, and Connecticut) and the District of Columbia (Lamont & Fitzgerald 2000; Price 2001). Fifteen additional states are currently at risk of becoming infested with this weed (Okay 1997). In the southern United States, mile-a-minute weed could behave as a perennial plant (Stevens 1994; Ding et al. 2000). Recently, mile-a-minute weed was targeted for biological control.

Several natural enemies of mile-a-minute weed have been recognized in China (Ding et al. 2004), but little information is available on other potential biological control agents from other regions of the plant’s large native range (Ohwi 1965; Satake et al. 2000). We examined the weed in Japan because parts of Japan are in the native range of mile-a-minute weed (Ohwi 1965) and those areas are a good climatic match to the northeastern United States, where release of natural enemies is intended (Reardon, unpublished data). Here we report the results of a survey made in 2004 and 2005 of the herbivorous insect fauna of mile-a-minute weed of Japan.

We selected our survey locations in Japan using data from the National Census on River Environments (1993-1999). We surveyed 15 sites, mainly in Kinki district (Table 1). Although most sites were sampled only once, in 2004, one site (Yawata city, Kyoto) was sampled several times over the course of the season. In 2005, we surveyed 1 site in Kinki district several times. Sample sites were distributed over 10 Prefectures and samples were collected between Apr and Nov.

For thorny vines of mile-a-minute weed sprawling on other vegetation, sweep net sampling was not feasible. Instead, timed visual searches were used as the sample unit (15 min per sample, 2 to 6 samples per site on a given sample date). Insects detected were captured for identification. Larvae were reared to adults on mile-a-minute weed in the laboratory (25C, a photoperiod of 16: 8 L: D).

We collected 50 herbivorous insect species (Table 2) on mile-a-minute weed: 11 Lepidoptera (22%), 26 Hemiptera (52%), 3 Orthoptera (6%), 9 Coleoptera (18%), and 1 Hymenoptera (2%). Of the total (except 4 species with unknown hosts), 30 species were clearly polyphagous and 10 were specialists on other plant families; these species clearly were not potential biological control agents. Six species appeared to be potential Polygonaceae specialists: (1) Two hemipterans, the bug Coptosoma parvipictum Montandon (Pataspidae) (Tomokuni 1993), found frequently at the Yawata city site, and the aphid Trichosiphonaphis ishimikawae (Shinji) (Aphididae) (Moritsu 1983), which was found in both years at many sites; (2) two lepidopterans, Timandra apicirosea (Prout) (Geometridae) and Oligonyx vulnerata (Butler) (Noctuidae) (Inoue et al. 1982), of which T. apicirosea was frequently found, whereas O. vulnerata was rarely collected; (3) one sawfly, Allantus luctifer Smith (Tenthredinidae) (Asahina et al. 1965), found in both years at many sites; and (4) one beetle, Rhinoncomimus latipes Korotyaev (Curculionidae) (Colpetzer et al. 2004a, 2004b) (Table 2).

Rhinoncomimus latipes was collected in 2004 at the Yawata site from May to Oct, with peak abundance in late-Jun and mid-Sep and was collected at 6 sites (Yawata, Matsuobashi, Ishiyama, Kizu, Sendai, and Sapporo). Larvae of T. apicirosea were observed from May to Sep and it was collected at 9 sites (Azuchi, Kizu, Matsuobashi, Takiyama, Yawata, Haijima, Kagoshima, Sendai, and Tochigi). The sawfly A. luctifer was collected mainly as eggs or larvae and was observed at 10 sites (Azuchi, Hirakata, Ishiyama, Matsuobashi, Takiyama, Yasu, Yawata, Hachioji, Haijima, and Shizuoka). Eggs of A. luctifer were inserted in or around leaf midrib veins and at the Yawata site peak egg abundance occurred in May and Jul.

Of the 6 specialist herbivores encountered, R. latipes appears to be the most promising agent to control mile-a-minute weed (Colpetzer et al. 2004a, 2004b). Two other species encountered, A. luctifer and T. apicirosea, appear less promising. A congener of T. apicirosea, Timandra griseata Peterson (Lepidoptera: Geometridae) from China, previously has been rejected as a biological control agent because it developed on common buckwheat, Fagopyrum esculentum Moench (Polygonaceae) and tartary buckwheat, Fagopyrum tartaricum Gaertn (Polygonaceae) (Price et al. 2003). The aphid T. ishimikawae, a Polygonaceae specialist, was abundant but switches hosts seasonally, using species of Caprifoliaceae in winter (Moritsu 1983). Therefore, this aphid would only establish where both necessary Polygonaceae and Caprifoliaceae hosts grow near each other. The remaining Polygonaceae specialists, C. parvipictum and O. vulnerata, were not abundant in our samples, and may have limited impact on mile-a-minute weed in Japan. However, it is possible their densities might increase after the introduction to the United States if their own natural enemies limit their Japanese densities.

Two leaf beetle species, Lema diversa Baly and L. concinnipennis Baly, that are oligophagous for Polygonaceae and that are common in China (Ding et al. 2004) have been reported from Japan (Hayashi et al. 1984), but were not collected in this survey. Although seed feeding species are known in China (Ding et al. 2004), none was collected in Japan.

We thank the USDA Forest Service for funding, and Kazuo Yamazaki (Osaka City Institute of Public Health and Environmental Sciences) for identifications of some insects, Yoshitaka Sakamaki (Graduate School of Agriculture, Kagoshima University) for identification of Calybites phasianipennellus, Hiroaki Kojima (The Kyushu University Museum) and Hiraku Yoshitake (Graduate School of Arts and Sciences, University of Tokyo) for identification of Rhinoncomimus latipes, and Yoshihisa Sawada (The Museum of Nature and Human Activities, Hyogo) for identification of some weevils. We thank several colleagues in our laboratory for the identification of some insects and for assistance in field survey, and in particular, Azusa Yamazaki, who surveyed mile-a-minute weed in Kagoshima and Shingo Tanaka, who surveyed in Sapporo.

Summary

Persicaria perfoliata is an annual plant of Asian origin, which is a serious invader of native and orchard plant communities in the eastern USA. Based on a 2-year survey of herbivores of this plant in Japan, a suite of herbivorous insects were collected. Six species, including 1 bug, 1 aphid, 2 moths, 1 sawfly, and 1 beetle, are considered as specialists on Polygonaceae.