103 - Underground Mosquito Control Strategies: Entomopathogenic Fungi and Attractive Toxic Sugar Bait in the Storm Drainage System of the Coachella Valley

Abstract: The past decade, Bill Walton spearheaded research into two novel, environmentally-friendly mosquito control strategies for underground storm drainage systems (USDS) of the Coachella valley in southern California. The first centered on entomopathogenic fungi applied to USDS walls to kill resting adults and the second on attractive toxic sugar bait (ATSB) stations lethal to sugar-feeding adults. Baseline efficacy tests were established in the laboratory against colony-raised Culex quinquefasciatus, the dominate species of wild mosquitoes found at USDS sites. Field studies revealed potential pros and cons of each approach, variable mosquito control outcomes over time and space, and environmental factors that likely shaped the USDS trends. Fungal studies, for example, tracked mortality of Culex quinquefasciatus females exposed in overnight chambers to vertical USDS walls treated with a spray formulation of either Beauveria bassiana, Metarhizium anisopliae, or water. Results over multiple seasons indicated mosquito infection/death varied by fungal species and the age/location/season of each treatment linked to localized and regional fluctuations in temperature and relative humidity. Secondly, ATSB studies with CDC-UV light traps (no carbon dioxide) indicated numbers of wild adult mosquitoes with bait dye varied by station design, age, and USDS structure. ATSB treated with Beauveria bassiana resulted in a spread of fungal infections in adults collected within and between USDS chambers, and residual infection after an overwintering period. Both control techniques are predicted to be enhanced in deeper USDS substructures protected from weather and human activity. Such sites would offer more stable temperatures and relative humidity and adult mosquitoes would be expected to take refuge in these conditions to enhance interception rate with treatments. Overall, surprisingly, experimental treatments were not associated with relative declines in wild mosquito production in weekly sampling regimes. The potential viability of fungus- and/or bait-based adulticides in mosquito abatement programs for USDS will be discussed.