Scads... it's not BT... bt is primarily for Lepidoptera... moths and such... I have a concern with mosquito spraying but not from a county standpoint... my neighbor, two houses down has a private company come and spray around there home. I never know when that will happen but it's always during the day light hours. When I see the truck at their house, I go remove the shims holding the telescoping top up for ventilation and I close the SBB for about an hour or so... hate doing it in the summer when it's 100 degrees... don't know if it helps or not... certainly no way to tell about the foragers that are out and about. I hope I never catch them spraying the standing water because we are only 1/8th of a mile from a large lake and groundwater contamination is strictly enforced since that lake is the primary reservoir for Columbia, SC and surrounding areas.