Commercial SEL is all that's required. Getting insurance is the hard part. It doesn't matter how much time you have, mainly what they want is ag time. It's the old case of, "If you haven't been there, you can't go." Unless you can find someone that's self insured, of course.

Aside from the airplane stuff, you still need a pesticide applicators license, issued by the state you're working in. Not terribly hard to get in most states, but it will take some study and passing a test.