Mosquitoes, including vectors of human and wildlife pathogens, interact with terrestrial plants throughout their life cycles. Inputs of leaf detritus into the aquatic habitat provide an energy base for developing larvae, and plants mediate the distribution of adult mosquitoes by influencing microclimate conditions, supplying sugar-feeding sources, and altering the abundance and composition of wildlife blood-meal hosts. Our research examines direct and indirect effects of understory shrubs, including both native and invasive species, on the ecology of an important regional vector for West Nile virus (Culex pipiens). We test the hypothesis that leaf detritus in the aquatic environment mediates two components of mosquito production (i.e., oviposition site selection and adult emergence) via the microbial assemblages associated with decomposing leaves. We then explore vector management applications of these findings, specifically 1) exploitation of ecological traps (i.e., leaf species that are attractive for oviposition yet deleterious to larval survival and development) for a novel attract-and-kill mosquito control approach in storm water environments, and 2) eradication of an invasive Amur honeysuckle (Lonicera maackii) to reduce mosquito abundance.
We found that leaf detritus from native and invasive plants in the aquatic environment varies in both its attractiveness and nutritional quality for Cx. pipiens. In particular, Amur honeysuckle yielded high oviposition and emergence rates; in contrast, we identified a native plant (common blackberry, Rubus allegheniensis) that functions as an ecological trap for Cx. pipiens, attracting gravid females to oviposit yet deleterious to larvae, yielding low emergence rates. Laboratory assays indicate the ecological mechanism underlying this variation in both oviposition and emergence rates across leaf species is related to the composition and abundance of bacterial flora associated with the different plants. A two-year field experiment demonstrated the viability of exploitation of a naturally-occurring ecological trap (blackberry leaves) and an artificial ecological trap (honeysuckle leaves mixed with Bacillus thuringiensis var. israelensis larvicide) for attract-and-kill mosquito control in storm water catch basins, increasing the relative abundance of Cx. pipiens larvae and decreasing the abundance of adults collected in these habitats. Finally, a two-year Before-After/Control-Impact experiment showed that eradication of Amur honeysuckle decreases abundance of Culex spp. and other mosquito genera in forest fragments embedded within a residential neighborhood, most likely via effects on local microclimate conditions and the passerine bird host community.