Well Guys Fencing laws can vary from State, County and Municipality across the country. I have studied the matter and in Iowa, for every paragraph that say's I'm not obligated to build a fence there is another that obligates me to do so.
While I do not keep livestock and may not be obligated to build a fence, my failure to do so if it resulted in his loss of stock or property loss could make me liabel. I've seen these disputes go all the way to the supreme court and more often than not You have to build the Fence.
The old Adage from a Robert Frost poem"Good Fences make Good Neighbors" holds true. Arguing the point would likely result in legal fees and his not being nearly as careful with spray drift. And who knows where from there. It's far easier to get along!!
I'll build the fence, I'm just wondering what it's costing around the country?
If your wondering what I'm up against here is a link to the Fencing law in Iowa.