Seasonal oviposition of Culex quinquefasciatus in proprietary belowground stormwater treatment systems in an urban area of southern California.

Belowground stormwater infrastructure has long been documented to harbor mosquitoes, including those capable of transmitting human disease pathogens (Harbison et al. 2010a). Culex quinquefasciatus Say is a widespread vector species found in the lower latitude regions of the world that is often associated with these subterranean habitats (Lines 2002, Montgomery et al. 2004, Giraldo-Calderón et al. 2008, Naeem-Ullah et al. 2010) and can present a public health concern in urban areas. While much of the published research concerning Cx. quinquefasciatus in belowground stormwater habitats has focused on the occurrence and/ or control of larval and adult stages in sub-surface catch basins and storm drain systems little is known in regards to the oviposition behavior of this species as it seeks to lay egg rafts within enclosed structures (Harbison et al. 2009, 2010b). Data on seasonal egg-laying would provide insight into the belowground ecology of Cx. quinquefasciatus and help guide timing of surveillance and control efforts. To this end, 26 months of ovitrap data collected in the neighboring cities of Ontario and Rancho Cucamonga, CA, were compiled to elucidate the seasonality of belowground oviposition in this area. As part of ongoing research of proprietary belowground stormwater treatment systems (STS), Cx. quinquefasciatus egg rafts were collected using bucket ovitraps (13-liter plastic buckets baited with ~1.5 liters of liquid mosquito attractant) floated singly in permanent water sumps as previously described by Harbison et al. (2010b). Twenty-nine STS were evaluated; 23 in Ontario and six in Rancho Cucamonga. Ovitraps were deployed overnight in STS two to nine Data collected during the second study period were from ovitraps deployed in the two permanent water sumps of a Vortechs ® Model 1000 (CONTECH Construction Products Inc. West Chester, OH) (Figure 1) located in Ontario. All egg rafts were removed and reared individually in small cups (ca 100 ml) to confirm larvae as Cx. quinquefasciatus. Data from both study periods were compiled, separated by month of collection, and the overall monthly mean number of egg rafts per ovitrap calculated. Ambient air temperatures and precipitation data were obtained from the weather station of the NOAA National Weather Service Forecast Office located at the Ontario International Airport and compared against egg raft counts to examine seasonal trends in egg-laying using a Kendall rank correlation test (Stata 9.2, StataCorp LP, College Station, TX). All STS were within six km of this station and at least 30 m from each other. …