The impact of wetland vegetation drying time on abundance of mosquitoes and other invertebrates

Vegetation management for constructed treatment wetlands often involves knocking down emergent vegetation with heavy equipment and inundating the dead vegetation after a period of drying. Such practices create favorable conditions for larval mosquitoes. We studied the relationship between length of the drying period for an emergent macrophyte, Typha sp., and the abundance of aquatic invertebrates in replicated 0.18-m3 wading pools. The mosquito, Culex tarsalis, was significantly more abundant in pools containing vegetation aged for 2 wk before inundation compared to pools containing vegetation aged 5 wk, freshly cut vegetation, or without vegetation. Potential larval mosquito food resources (particles between 2 and 61 microm in equivalent spherical diameter) in the 2-wk aging treatment did not differ significantly from the other treatments during the 5-wk experiment. The abundance of other larval culicids, nonculicine Diptera, and potential mosquito predators (i.e., Dytiscidae and Aeshnidae) did not differ significantly among the vegetation aging treatments.