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

Authors: MACKAY, ANDREW - University Of Illinois; Muturi, Ephantus; MOEN, ELEANOR - University Of Illinois; HOLLAND, MATT - University Of Illinois; ALLAN, BRIAN - University Of Illinois

Submitted to: Wetlands Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2021
Publication Date: 9/21/2021
Citation: Mackay, A.J., Muturi, E.J., Moen, E.M., Holland, M., Allan, B.F. 2021. Influence of vegetation and vegetation management on Culex mosquitoes in surface stormwater habitats. Wetlands Ecology and Management. https://doi.org/10.1007/s11273-021-09829-1.
DOI: https://doi.org/10.1007/s11273-021-09829-1

Interpretive Summary: Stormwater ditches and dry detention basins (DDBs) are common tools for managing urban runoff and are frequently colonized by mosquitoes that transmit West Nile virus (WNV). These structures are traditionally landscaped with managed turfgrass in residential and commercial development, but are also susceptible to colonization by native and invasive species of cattails. Cattails are common in urban drainage infrastructure and other disturbed aquatic habitats with high nutrient enrichment where they can form dense monotypic stands. Both turf and invasive ground cover may be periodically mowed in ditches and DDBs during the growing season to maintain aesthetic or safety standards, limit growth of undesirable flora, and to improve water quality and hydraulic capacity. This practice can generate a large biomass of plant litter that can be submerged following storm events or transported to adjacent aquatic habitats. This study investigated the consequences of cattails and turfgrass and their management practices on the ecology of mosquitoes in stormwater structures. Mowing was associated with higher mosquito abundance, with mowed turfgrass supporting more mosquitoes compared to mowed cattail. Decomposing cattail litter was less preferred by egg laying female mosquitoes compared to decomposing turfgrass litter and supported smaller adult mosquitoes with reduced fitness and an expected lower potential to transmit WNV. These findings demonstrate that mowing practices in surface stormwater best management practices may pose substantial public health risks by enriching the aquatic habitats and increasing their capacity to produce the mosquito vectors of WNV. Results also indicate that displacement of conventional turf cover by cattails is likely to diminish this risk.

Technical Abstract: 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.