I would be curious as to know what they're doing with the berries? surely with this amount of berries is not for their own personal use, how ever It wouldn't make since either that they would be selling them to local markets, when I'm sure the markets already knows about your established berry farm and they could simply buy directly from you,
Just because they are neighbors to your farm property doesn't give them rights to help themselves to your berries,
I would try and find out if these people have been steeling from you only to sale them on the open markets,
Look on the local C-List for Blueberries for sale? if so fallow up on who is selling them, find out if they travel outside of town to sell the berries, Find out if anyone in their family or any friends has a country store somewhere etc,etc, Find out how long they have been providing them? if you can prove they been making money from selling your berries ( stolen berries) you might have another charge to hang on them,

and might be more money due back to you,
BTW , we have a small Blueberry orchard and cannot give them away fast enough before they fall to the ground and go to waste, But I wouldn't give them to a neighbor who would think nothing of steeling from me,