SC is right about small town south, USA. If you call in the authorities, your name is mud. We have to take care of our own problems, or face exile. It dates back to when the moonshiners helped neighbors who were down and out, so no one wanted them caught.
Going to the local coffee house and badmouthing the farmer about recklessly spraying and killing the bees would have a much better effect, AFTER talking to the farmer and getting nowhere with him.
What Iddee said.. You dont EVER call in authorities in a small town like the one I live in. There is usually nothing they can do anyhow.. they need PROOF POSITIVE of any wrongdoing.. all YOU need is word.. meaning word spreads, and people talk.. if you are in good standing, someone is going to come to you and say.. HEY! This is what I just heard from such and such... then you can ask questions, and it doesnt take long to be perfectly content with your knowledge, and then go confront the perpetrator.. 97% of the time he will work to make amends, the other 3% of the time its a KID who doesnt yet understand the situation, so you go to his/her parents and that is usually enough to get things fixed...
Pesticide spraying in this state by a commercial applicator is not legal within one mile of a registered apiary.. I have apiaries spread out so that I have about six miles around the town covered... However, that doesnt stop a private individual from spraying right over top of my hives LEGALLY, giving me no recourse...
Enter the statement above -- I have spoken with and personally KNOW all landowners around this town, there are actually not that many.. They all have my number, they all know to call me if they are going to spray insecticides.. If they fail to call me, and I confront them, they offer to pay for the hive for forgetting. I have never accepted payment, I just ask not to forget again... I often even get calls from people IN town who want to spray their gardens..
The fact is, MOST sprays being applied now are not immediately lethal to honey bees. (orchards not withstanding. I have no clue what is sprayed on orchards.) Herbicides like Roundup or 24d dont leave dying bees outside your hive. the stuff that does that is now mostly incorporated, or systemic. Giving you time to rotate out older comb before it can become a problem.
Most issues I have witnessed personally, were from gardens. People applying SEVEN dust or other insecticides when their tomatoes are in bloom etc.. Thats when I find three hundred dead bees in front of my hive. SEVEN dust, and Bayer advanced complete insect killer being two of the worst to date. the bees LIKE the dust and fly it back to the hive as if it were pollen.... Of course, that makes finding it in the hive pretty easy.