Influence of vegetation and vegetation management on Culex mosquitoes in surface stormwater habitats

Stormwater drainage infrastructure creates abundant, nutrient-rich habitats in urban landscapes vulnerable to colonization by undesirable organisms, including vector mosquitoes and invasive aquatic macrophytes. The overall aim of our study was to identify consequences from cattails ( Typha spp.) and their management to the seasonal abundance and adult fitness parameters of Culex pipiens and Cx. restuans developing in these surface stormwater habitats. We surveyed juvenile mosquitoes in 36 stormwater management structures (ditches and detention basins) with differing plant species composition and frequency of mowing. Effects of litter biomass, litter type (cattail, turfgrass) and exogenous enrichment with orthophosphate on oviposition site selection were evaluated in aquatic mesocosms. Individual laboratory experiments investigated effects of litter factors on juvenile development rate and survivorship, and adult body size and starvation resistance. We observed a greater abundance of both Cx. pipiens and Cx. restuans larvae in stormwater management structures with recently mowed vegetation. Additionally, we found a significant interaction between mowing and dominant plant type for Cx. pipiens , with the greatest number of larvae observed in mowed turfgrass habitats. For both Culex species, increasing litter biomass and the addition of orthophosphate enhanced oviposition rates in mesocosms, but the two species differed in their relative response to litter type. Similarly, we detected differences in the effects of litter type and biomass on Cx. pipiens and Cx. restuans development and adult fitness traits. Our results suggest asymmetrical effects from invasion and management of cattails in stormwater ditches and detention basins on potential risks posed by these two vector species.