Surveillance, Larvicide Evaluations, Adulticide Studies, and Sibling Species Composition of Riceland Mosquitoes

Successful control of riceland mosquitoes requires knowledge of species and numbers of mosquitoes present, as well as selection of the management strategy to apply to a given area. Four studies were conducted in rice-growing regions of AR and MS during the summers of 2007 and 2008 to gain a better understanding of riceland mosquito surveillance, response to larvicides and adulticides, and sibling-species present in selected locations. One objective was to compare the effectiveness of three residential mosquito traps at capturing wild mosquitoes in riceland areas. Significant differences existed among trap types in regards to species and total mosquitoes captured. Another objective was to evaluate and compare the efficacy of two formulations of an experimental spinosad larvicide with that of two similar formulations of methoprene against Psorophora columbiae (Dyar and Knab) mosquito larvae in small rice plots. The experimental spinosad formulations proved more effective than did the methoprene formulations, providing up to 33 days of effective residual control. A third objective was to determine susceptibility levels of Anopheles quadrimaculatus Say adult mosquitoes from four locations in AR and MS to five adulticides (two organophosphates and three synthetic pyrethroids). Mosquitoes from these areas were highly susceptible to the synthetic pyrethroids, but mosquitoes from some locations exhibited significant tolerance to the organophosphate compounds. A final objective was to determine the sibling-species composition of the An. quadrimaculatus complex and correlate species type with adulticide susceptibility at selected rice-growing areas in AR and MS. However, only An. quadrimaculatus s.s. was present in the study, thus prohibiting the establishment of a correlation between species type and adulticide susceptibility.