Research on invasive insects has long focused on the direct interactions such as predation or parasitism. This is partly because many weed control projects showed the unsuccessful establishment in herbivorous insects specializing invasive plants through native natural enemies. However, there is increasing appreciation of the importance of plant-mediated indirect effects in determining abundance of insect herbivores. We examined (1) how the lacebug, Corythucha marmorata, indirectly affects leaf consumption by the leaf beetle, Ophraella communa, on the ragweed, Ambrosia artemisiifolia, and (2) how the predacious lady beetle, Harmonia axyridis, influences the indirect interaction between both insect herbivores.
Kudzu, Pueraria montana (Lour.) Merr. var. lo bata (Willd.) Maesen et S. Almeida (Legumino sae), is an aggressive invasive weed introduced to the United States in the early 20th century for forage and erosion control (Piper 1920). Kudzu turned out to be harmful, causing economic loss and suppressing native plants (Alderman 1998). The USDA removed it from the list of recom mended ground cover plants in 1953, and it was listed as a U.S. federal noxious weed in 1998 (U.S. Forest Service 2008). Kudzu infests 7 million acres in the United States (Miller & Edwards 1983; Britton et al. 2000), and kudzu's range in North America is still expanding. Sun et al. (2006) identified plant pathogens and 116 insect species associated with kudzu in China, and Tayutivutikul & Kushigemati (1992) made a similar survey in the southwestern part of Japan, and noted that 109 insects and 2 spider mites in Japan feed on kudzu. Here we report the first field surveys for kudzu-feeding insects in central Japan (12 sites in the Kinki District, N34?-36?, E135?-137?; 4 sites in Shiga prefecture, 3 sites in Kyoto prefecture, 2 sites in Hyogo pre fecture, and 1 site in Osaka and Nara prefecture), and in other regions (7 sites, N31?-42?, E130? 141?; 1 site in Hokkaido, Miyagi, Toshigi, Shi zuoka and Kagoshima prefecture, and 2 sites in Tokyo prefecture). Timed visual searches in plots with kudzu were conducted from May to Oct in 2004-2005. Three to 6 plots (2-15 m2) were marked per site, and each was searched for 15 min in 2004 and 5 min in 2005. The total time spent searching was 2050 min in the Kinki District and 395 min in
Water logging injury is a significant problem in soybean (G. max Merr.) production in Japan, because it is cultivated mostly in the converted paddy field. Wild groundnut (G. soja Sieb. et Zucc.), an ancestor of soybean, is growing around paddy field as a weed throughout the country. In order to evaluate waterlogging injury tolerance as a genetic resource for soybean, root and shoot growth in wild groundnut were investigated under the treatments by raised groundwater level upto soil surface for 21 days at the primary leaf and the flowering stages compared with soybean (cv. Ryuho). At the end of treatment of primary leaf stage, root length density (RLD) increased to 320%, and shoot dry matter weight per plant (DMW) decreased to 31% against no-treatment in wild groundnut, while influences on RLD and DMW were inconspicuous in soybean. It was considered that wild groundnut responded to excess water stress by increasing lateral root with root formation. At the end of treatment of flowering stage, RLD and DMW were not influenced in either species. However, the number of root nodules decreased greater in wild groundnut than in soybean, suggesting the difference in susceptibility to waterlogging injury at the flowering stage between these species. Reduction in leaf chlorophyll content by the treatment was observed continuously until maturity stage only in wild groundnut. At the maturing stage, grain yield in wild groundnut and pod number in soybean were measured to determine recovery from damages by the treatments. In wild groundnut, grain yield was equal to no treatment as well as pod number of soybean, and decreased to 15% by the treatments at the primary leaf and the flowering stages, respectively. However in soybean, pod number decreased to 54% by treatment at the flowering stage. Considering the severe damage in DMW at the end of treatment of primary leaf stage, wild groundnut showed higher ability to recover from the damage by the treatment than soybean. Consequently, it was suggested that waterlogging tolerance in wild groundnut might be related to the amount and the activity of root. Importance of root aerenchyma for waterlogging tolerance in soybean have been reported by many researchers. Therefore root development including aerenchyma formation under flooded condition should be investigated to utilize wild groundnut as a genetic resource of waterlogging tolerance for soybean.
Water logging injury is a significant problem in soybean (G. max Merr.) production in Japan, because it is cultivated mostly in the converted paddy field. Wild groundnut (G. soja Sieb. et Zucc.), an ancestor of soybean, is growing around paddy field as a weed throughout the country. In order to evaluate waterlogging injury tolerance as a genetic resource for soybean, root and shoot growth in wild groundnut were investigated under the treatments by raised groundwater level upto soil surface for 21 days at the primary leaf and the flowering stages compared with soybean (cv. Ryuho). At the end of treatment of primary leaf stage, root length density (RLD) increased to 320%, and shoot dry matter weight per plant (DMW) decreased to 31% against no-treatment in wild groundnut, while influences on RLD and DMW were inconspicuous in soybean. It was considered that wild groundnut responded to excess water stress by increasing lateral root with root formation. At the end of treatment of flowering stage, RLD and DMW were not influenced in either species. However, the number of root nodules decreased greater in wild groundnut than in soybean, suggesting the difference in susceptibility to waterlogging injury at the flowering stage between these species. Reduction in leaf chlorophyll content by the treatment was observed continuously until maturity stage only in wild groundnut. At the maturing stage, grain yield in wild groundnut and pod number in soybean were measured to determine recovery from damages by the treatments. In wild groundnut, grain yield was equal to no treatment as well as pod number of soybean, and decreased to 15% by the treatments at the primary leaf and the flowering stages, respectively. However in soybean, pod number decreased to 54% by treatment at the flowering stage. Considering the severe damage in DMW at the end of treatment of primary leaf stage, wild groundnut showed higher ability to recover from the damage by the treatment than soybean. Consequently, it was suggested that waterlogging tolerance in wild groundnut might be related to the amount and the activity of root. Importance of root aerenchyma for waterlogging tolerance in soybean have been reported by many researchers. Therefore root development including aerenchyma formation under flooded condition should be investigated to utilize wild groundnut as a genetic resource of waterlogging tolerance for soybean.
