Ask yourself: 'What would the Crays have done?'.....
No in all seriousness, go round and say that some of the other neighbours are really pissed off that their crops are going to get ruined, but you talked them out of doing anything drastic. For now. Suggest that maybe the best thing would be to get it gone before they all go mediaeval on his ass.
If he blows you off, go tell all the neighbours he said they could suck his balls. Then everybody's pissed at him, everyone's a suspect and you can apply paraquat, glysophate, agent orange etc without it being traced directly to you.