The Collier County Mosquito Control District was issued a warning by the Florida Department of Agriculture, after a complaint investigation found three violations in 2017 - one of the worst mosquito seasons in years.
One of the violations occurred April 20, when a 910-acre area around Marco Island was over-sprayed with the pesticide Zenivex during a mission.
Robin King, spokeswoman for Collier Mosquito Control, said the extra amount was small, but that they have since reduced the flow-rate on their helicopter to avoid overspraying.
"For the public, there would have been absolutely no effect on people, animals, or our environment," King said.
Another violation cited in the warning letter found that Collier Mosquito Control lacked a standard operating procedure to properly count mosquito populations along the shoreline.
King said they established a new procedure in January. But she said that so far this year, there haven't been that many salt marsh mosquitoes to count.
"We're not seeing them this year - we actually have to go out looking for them," King said. "This time last year, we were looking at counts well over 150 mosquitoes per minute."
She said it's possible that Hurricane Irma may have washed many salt marsh mosquito eggs from the mangroves back out to sea.
A third violation listed by the state's Agriculture Department found that Collier Mosquito Control did not keep a record of who loads the pesticides onto their aircraft. King said that has since been corrected.