Federal and state health officials say that pesticide spraying for adult mosquitoes has reduced risk of West Nile virus by killing specific percentages of mosquitoes. When confronted with Freedom of Information Act requests for the data to back up those claims, they do not seem to be able to find any.

"Massachusetts boasted a 60 percent kill rate. Vermont claimed up to 69 percent. And, in Texas, a preliminary report suggested that aerial spraying of pesticides eliminated 93 percent of disease-carrying mosquitoes in some neighborhoods.

Over the last couple months, officials from across the country have engaged airplanes armed with pesticides in an attempt to battle mosquitoes that carry the West Nile virus, on track to infect more people this year than ever before in the U.S., and eastern equine encephalitis, a less common but generally more dangerous disease. The decisions to spray have often been made under heated opposition from residents and some scientists concerned about what they say is an ineffective and unsafe strategy. Nevertheless, in at least a few cases, officials subsequently reported high success rates and few health complaints. ...

Some remain skeptical, going as far as to threaten legal action."

Lynne Peeples reports for Huffington Post September 18, 2012. [2]