Larvicide-mediated oviposition and ovicidal activity among treehole and container-inhabiting mosquito (Diptera: Culicidae) species.

Abstract

Larval application of insecticides (larviciding) is primarily conducted using a variety of biorational compounds as an essential function within integrated mosquito management. Larvicide-treated water has been sporadically investigated for deterring oviposition, but prior efforts have been primarily focused on Aedes aegypti (L.) with limited representation by other peridomestic or treehole species. A series of laboratory assays were conducted using 20 lb/acre (22.4 kg/ha) treatments of Lysinibacillus sphaericus (VectoLex FG), spinosad (Natular G30), and methoprene (Altosid XR-G Ultra) and compared to an untreated water option. These treatments were offered as a no-choice assay for Ae. aegypti in the laboratory and in an additional multi-choice test for Ae. aegypti, Aedes sierrensis (Ludlow), and Culex pipiens L. Significantly fewer Ae. aegypti eggs were collected from water treated with L. sphaericus in both the no-choice and arena tests. Significantly fewer Cx. pipiens eggs were deposited in water treated with methoprene, coinciding with elevated collections in water treated with spinosad. As a first report for the species, no significant trends were observed with Ae. sierrensis. Hatching eggs from spinosad and methoprene-treated water yielded lower success for both Aedes spp. We propose that gravid mosquitoes have some sensitivity towards certain larvicides and Aedes spp. eggs suffer ovicidal effects in treated water sources. Push effects may confound geotagged surveillance networks, such as for treehole and backyard mosquito species in peridomestic environments. However, we report that these preferences do not significantly impact ongoing control operations.