Here, in the U.S., there are certain, selected, State National Guard units (they're just like the real armed forces but are made up of local volunteers who do everything the full time soldiers do) that fly the C-130 Hercules aircraft.
Often, the National Gurad units are among the first called up in any kind of emergecny) fly the C-130 Hercules. These selected units have been authorized by the civilian Federal Aviation Administration (FAA) to spray chemical on areas experiencing mosquito infestations and some times cankerworms as well (they can destroy whole forests). They begin the day previous by flying very low over the area (including cities, golf courses, etc.) and using the GPS to mark any obstructions. They finish up the following night, since the mosquitos are more active then, by spraying the routes that were marked electronically the day previous. They're at an altitude of below 200 feet above the surface. Surprisingly, considering the engines each produce 4,000 horse power, they're reasonably quiet.
The work is normally done by small, civilian airplanes, but the C-130's have to come out to remote locations to apply the spray to Army and Air Force bases anyway, so they're doing it as a civic service... greatly appreciated, of course...