Mosquito Populations Decline

Below is the summary of mosquito activity in Iowa from the ISU Medical Entomology Laboratory. During the summer months, the Iowa State University Medical Entomology Laboratory monitors mosquito populations and mosquito-borne diseases in Iowa.   Mosquito collection data can be viewed online at the Iowa Mosquito Net


It is clear from the graph below that mosquito populations in Iowa are still on the decline from the dramatic peak in early July. The decline is due mostly to the gradual die-off of the massive numbers of floodwater mosquitoes that were hatched a month ago following widespread flooding and accumulation of water in temporary impoundments.  Mosquito trap collections are markedly low in every one of our surveillance counties.


The numbers of floodwater species (Aedes vexans, Ae. sticticus, and Ae. trivittatus) have died off so significantly that in some areas (e.g., Scott County trapping sites) they are no longer the dominant species. Floodwater mosquitoes are being replaced by Culex species and other container-breeder species. In the most recent trap catches there is a wider array of species and species diversity is higher than it has been all year. From our entomological perspective, it makes things very interesting!  That also increases the chances of late summer west Nile virus which is transmitted by container-breeding mosquitoes, primarily Culex species.  So far, only 1 collection of mosquitoes has tested positive for West Nile virus. That was a group of Culex pipiens in Ames a month ago. 


Read more about West Nile Virus at the Iowa Department of Public Health website and at the CDC.  



Mosquito trap catch data from the ISU Medical Entomology Laboratory, August 8, 2014.Mosquito trap catch data from the ISU Medical Entomology Laboratory, August 8, 2014.


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