Master of Science (MS)
Spinosad is a relatively new insecticide with a unique mode of action that is being evaluated for control of larval mosquitoes. Whereas a number of toxicological studies have measured effects of spinosad on various mammals, fish, birds, and terrestrial arthropods, fewer studies have been conducted on the effects of spinosad on non-target aquatic insect species. Such studies are important as these species might be found in the same environments as mosquito larvae targeted for control. A neighborhood pond was surveyed to find a representative species of mosquito as well as other common aquatic insects with which to examine susceptibility to spinosad and non-target effects. The mosquito species chosen was Culex quinquefasciatus and the most common non-target taxa were immature stages of a mayfly (Caenis spp., Ephemeroptera: Caenidae), a damselfly (Ischnura spp., Odonata: Coenagrionidae) and a dragonfly (Pachydiplax longipennis, Odonata: Libellulidae). Bioassays of mosquitoes from a reference susceptible strain (Sebring-S) and field-collections of C. quinquefasciatus were used to determine susceptibility to spinosad. In addition, susceptibility was examined in non-target taxa using spinosad concentrations corresponding to the LC50 of a field-collected mosquitoes (0.031 ppm) and the labeled rate (1.6 ppm) of Natular®, an EC formulation of spinosad. Susceptibility to spinosad did not differ between Sebring-S and field-collected mosquitoes. However, there was a marked difference in susceptibility among non-target taxa. Susceptibility was greatest in Caenis spp., followed by Ischnura spp., then P. longipennis. Results from this study will allow better future management strategies for the use of spinosad as a mosquito larvicidal agent.
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Jones, Owen McBride, "The effects of spinosad on Culex quinquefasciatus (Diptera: Culicidae) and non-target insect species" (2012). LSU Master's Theses. 2619.