Efficacy and Nontarget Effects of a Spinosad-Based Larvicide in Minnesota Vernal Pools and Cattail Marshes.

Larvicides that contain spinosad, a bacterial metabolite, are used to control mosquitoes in diverse aquatic habitats. These same habitats are home to other invertebrates, including Crustacea-fairy shrimp, isopods, and amphipods-and mollusks-fingernail clams and freshwater snails. A double-blind study evaluated the effects of Natular® G, a granular treatment containing spinosad, on spring Aedes spp. and nontarget invertebrates in vernal wetlands. Within 14 days after application, Natular G controlled larvae of spring Aedes by 53-84%, depending on species, but had no significant effects on numbers of fairy shrimp, fingernail clams, or freshwater snails. A second double-blind study evaluated effects on Coquillettidia perturbans and nontarget isopods and amphipods in cattail marshes. Treatment reduced emergence of Cq. perturbans by 25% but did not change numbers of isopods or amphipods. The 2 experiments indicate Natular G could be effective against spring Aedes in vernal wetlands, less so against Cq. perturbans in cattail marshes, and yet pose minimal risk to crustaceans and mollusks in either vernal wetlands or cattail marshes.

Status of Aedes japonicus in the Metropolitan Mosquito Control District, Minnesota.

ABSTRACT. The Asian exotic mosquito Aedes japonicus was 1st collected in Minnesota in 2007 and was well established in parts of the Metropolitan Mosquito Control District (MMCD) by 2008. Surveillance strategies were devised for 2009 to track the expansion of its range through MMCD and to direct control efforts. Sampling of larvae from container and tire habitats was the primary method used to document Ae. japonicus presence, but larvae were found in other habitats as well. Adult Ae. japonicus were collected by vacuum aspirator, gravid trap, and New Jersey trap but not by CO2-baited Centers for Disease Control and Prevention light trap. Aedes japonicus were collected from each of the 7 counties surveyed; in 5 of the counties for the 1st time in 2009. Preliminary findings suggest that a control strategy involving intensive source reduction can reduce Ae. japonicus populations.