This is a very thorough indictment of the expansive tendency in mosquito spraying. We give just a few excerpts here. Please see the full article for all details.

A Beyond Pesticides Factsheet

While communities have good intentions, many existing policies and programs may be dangerous to children, adults and wildlife and inadequate by relying too heavily on spraying pesticides to kill adult mosquitoes….

Less than one percent of those infected with WNv will develop severe illness, according to the Centers for Disease Control. The vast majority of people (about 80%) who become infected with WNv will show no symptoms and never become sick. Some 20% may experience mild flu-like symptoms within 3 – 15 days….

A person who has been infected with WNv may have life-long immunity even if they show no symptoms….

PESTICIDE SPRAY PROGRAMS ARE INEFFECTIVE

According to the Centers of Disease Control and Prevention (CDC), spraying adulticides, pesticides intended to kill adult mosquitoes, is usually the least efficient mosquito control technique.

Adulticiding programs spray pesticides indiscriminately and do not get at the mosquitoes until they have matured. They also do not restrict, control, or prevent mosquitoes from carrying WNv or continuing to breed.

Close to 99.9 % of sprayed chemicals go off into the environment where they can have detrimental effects on public health and ecosystems, leaving 0.10% to actually hit the target pest.

Mosquitoes develop resistance to pesticides over time, rendering the chemicals ineffective. A 2003 study finds that mosquitoes carrying West Nile virus and malaria developed resistance to organophosphate and carbamate insecticides as a result of a single genetic mutation.

After Hurricane Floyd caused a surge in mosquito populations in Florida, state officials took bite counts before and after widespread aerial spraying and found that mosquito populations surged back to pre-spray levels within three days of the treatment….

In 2003 the city of Boulder, CO did not adulticide and showed an 80% reduction in mosquito populations and lower rates of serious illness per population than surrounding cities where adulticiding took place….

see lots more info, including non-toxic methods of mosquito control, at Beyond Pesticides