Monday, December 10, 2007 - 8:17 AM

Size matters: Effects of vegetation plot size on larval mosquito predators

Jennifer Henke, and William E. Walton, University of California - Riverside, Department of Entomology, Department of Entomology, University of California Riverside, Riverside, CA

Created wetlands are often planted with vegetation, creating microhabitats suitable for the production of large numbers of mosquitoes. Previous studies have found that wider bands of vegetation reduce the efficacy of Gambusia affinis, the mosquitofish, to control larval mosquito populations. This study examines the effects of vegetation patch size on two other predators of larval mosquitoes, backswimmers (Hemiptera: Notonectidae) and arroyo chubs (Gila orcutti). The arroyo chub was chosen since it is native to southern California with a capacity to control larval mosquitoes, and is a species of special concern due to urbanization and to competition with introduced fish. Twelve ponds at the UC Riverside Agricultural Experiment Station received additions of Schoenoplectus californicus in one of two arrangements such that 12 0.1m2 (or single plant) plots, 4 0.4 m2 (or four plant) plots, and 2 0.9 m2 (or nine plant) plots were present. All twelve ponds received additions of Notonecta. Six ponds received additions of 30g of G. orcutti. Samples taken through April show that ponds with fish have significantly fewer larval mosquitoes than ponds with fish (p=0.0570). While there was not a significant fish X vegetation plot size interaction, the 0.4 m2 consistently had more mosquitoes than the 0.1 m2 plots, though neither significantly differed from the largest plots. Samples were taken throughout the summer and are currently being sorted to ensure seasonal control of larval mosquitoes.

Species 1: Diptera Culicidae Culex tarsalis
Species 2: Diptera Culicidae Culex quinquefasciatus (southern house mosquito)
Species 3: Diptera Culicidae Culex stigmatosoma