Master of Science (MS)
The rice stink bug (Oebalus pugnax) is the major pest of late-season rice in Louisiana. Prior studies indicate that large populations of mosquitoes are often present in rice fields during the time that rice fields are infested with rice stink bugs. Lambda-cyhalothrin (Karate®) is widely used to control rice stink bugs. The purpose of this study was to determine if application of the insecticide Karate® at a rate of 0.033 kg/ha, for rice stink bug control had an effect on the population of mosquitoes in rice fields. This effect was assessed by monitoring natural populations of mosquitoes before and after applications of Karate® in simulated rice paddies at the LSU AgCenter Rice Research Station (Crowley, Acadia Parish, Louisiana) during the summers of 2003, 2004 and 2005. In 2005, monitoring of native mosquito population was complemented by the use of sentinel cages with Culex quinquefasciatus Say larvae and exposure of Cx. quinquefasciatus larvae to treated rice field water in the laboratory. The number of larvae in Karate® plots decreased after Karate® applications but a significant overall effect was observed only after the first application of 2004 (p=0.034). Mortality of larvae in sentinel cages (p=0.0386) and of larvae exposed to rice field water at 48hrs (p=0.0130) was also observed in some cases. A test conducted in a large rice plot with sentinel cages confirmed the effect of Karate on mosquito larval populations (p=0.0012). An additional effect of foliar Karate residues on adult Cx. quinquefasciatus mosquitoes was observed in the laboratory (2004, 2005). Higher mortality was detected in adults exposed to rice foliage treated with Karate than the untreated control. Another factor that could influence the number of larvae present in rice fields is the oviposition response of mosquitoes to the presence of predatory insects. To test this response, Cx. quinquefasciatus adult mosquitoes were exposed in cages to water conditioned by previous exposure to potential aquatic predators. According to the Oviposition Activity Index (OAI), female mosquitoes preferred to lay eggs in water conditioned water rather than distilled water. The highest OAI was obtained with the Hydrophilidae-conditioned water.
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Cuadra, Ana Maria Sanchez de, "Factors potentially influencing the abundance of mosquitoes in Louisiana rice fields" (2008). LSU Master's Theses. 3829.