Attrition of rice stink bug (Hemiptera: Pentatomidae) cohorts and impacts of barnyardgrass management and application of selected insecticides on survival of the egg parasite Telenomus podisi Ashmead (Hymenoptera: Scelionidae)

Three experiments with the rice stink bug (Oebalus pugnax F.) were conducted in 1990 and 1991 at the Rice Research and Extension Center, Stuttgart, Arkansas. The general objective was to determine the attrition of the rice stink bug populations and to explore the impact of barnyardgrass (Echinochloa crus-galli (L.) Beauv.) management and application of insecticides used in rice (Oryza sativa L.) on the survival of the egg parasite Telenomus podisi Ashmead.;The first experiment was to examine attrition and survivorship patterns of the rice stink bug. Records also were taken on rice stink bug egg and nymph development time, sex ratio and mortality in the absence of natural enemies, and egg placement in barnyardgrass and rice canopies. The predominant mortality of the rice stink bug eggs on barnyardgrass and rice was caused by T. podisi, an egg parasite, which accounted for 36-71% and 43-63% mortality in 1990 and 1991, respectively. The highest mortality percentage of rice stink bug nymph cohorts occurred in the first instar (38-58%). Cumulative mortality of instar 1 to 4 was 72.5-78.8% in 1990 and 66.5-80.3% in 1991. Predators observed feeding on rice stink bug nymphs were larvae and adults of convergent lady beetle (Hippodamia convergens Guerin), green treefrog (Hyla cinerea Schneider), and spiders.;The second experiment was to determine the effect of sequential mowing, at 5-10 day intervals, on the period of barnyardgrass panicle development. Results suggest that sequential mowing could delay the heading of barnyardgrass as late as the first week of September. Mowing conducted later in the season, however, tended to lower numbers of panicles and reduce the size of panicles.;The third experiment was to determine in the laboratory the relative toxicity of carbaryl (Sevin XLR), methyl parathion, and encapsulated methyl parathion (Penncap-M) to stink bug embryos (eggs) and immature T. podisi inside rice stink bug eggs. The 3-5 day old immature T. podisi were more susceptible to all three insecticides than 7-9 day old immature T. podisi. Overall results suggest that methyl parathion was the least harmful insecticide to immature T. podisi and the most toxic to the rice stink bug eggs or emerging nymphs.