Can I stop crop dusters repeatedly flying over my home?
In a rural area pilots can fly pretty low, and are permitted to fly even lower while carrying out a lawful activity such as crop-dusting. Even if the pilot flew at 500 feet above your house, which is probably the maximum that he needs to stay away, it would still be loud and disturbing to your livestock. 

You should try to work it out with the company and/or the pilot in an amicable way.  

Unless your house is located in a congested area, the minimum altitude the pilot must maintain is 500 ft. However, if your house is located in a sparsely populated area, the pilot may be able to fly much lower than that. However, while the pilot is in the process of spraying, or turning around to spray he is allowed to fly lower than that minimum. Otherwise, the pilot may have to do dangerous steep climbs and descents.

For example, lets say the pilot is in violation of minimum altitude regulations by flying over your house at some minimal altitude below 500 ft. Lets assume you get the pilot busted and the pilot receives a warning, citation, or temporary suspension. When he comes back he can just fly over at 500 ft legally all day long, and that will probably be almost as noisy and disturbing to your livestock. 

Alternatively, you can lease a small part of your land to AT&amp;T to put a 1000ft tall cellular antenna on your property.

But seriously, as a pilot, if I heard that my flying was causing you so many problems, I would try to avoid it as best as possible, so long as it doesn't affect safety.