It depends on the pesticide they are spraying. Here in Dallas, they allegedly use something that breaks down quickly in sunlight. They also have a registry for beekeepers. You put in the location of hives and they allegedly skip spraying in your immediate area. But with wind drift and human error, I'm not sure how well that works. Some people cover the hives with a tarp for the night when spraying is planned. That may have some adverse effects, too, particularly when the weather is hot. Spraying seems to me a very expensive proposition with little effect, since it doesn't do anything to kill the millions or billions of mosquito larvae, but it makes somebody feel good and it looks like the politicians are doing something.