Seasonal attraction of the rice bug, Leptocorisa chinensis Dallas (Heteroptera: Alydidae), to synthetic attractant

Abstract

To improve the procedures for estimating the abundance of the rice bug, Leptocorisa chinensis Dallas (Heteroptera: Alydidae), field monitoring using traps baited with synthetic attractant was conducted in Tsukuba, central Japan from 2002 to 2006. A mixture of (E)-2-octenyl acetate and 1-octanol, in a ratio of 5 : 1 and incorporated into a plastic pellet, was used as bait on sticky boards and placed at study sites from early June to the end of October. The attractant-baited traps were able to detect the starting of the migration period of the overwintered generation and the population increase of the first generation. The number of trapped insects decreased rapidly after early September, while the number of insects in second generation increased in the grassy weeds field. The decreased temperatures and shorter day-length of autumn (which will have induced reproductive diapause) may have affected the attractiveness of the baited traps. The ratio of males to all captured L. chinensis was 0.88–0.96. Most captured adults had no food in their stomachs, and most males were sexually mature. These results indicate that the males trapped had actively moved for two possible reasons: to search for food and/or to search for females. Based on comparisons between the results of baited trap monitoring and sweep-net surveys, it was considered that immigrant period and density of L. chinenis in the poaceous plants fields depend on the density of dispersal individuals and the heading period of the plants.