How about just muzzling the mini? There are fruit trees in my pasture and I muzzle him with the best friend muzzle and all is good :)
We have pastures we rotate, and keep the horses out of the one with the apple tree. If the pasture is short, and we need that pasture, we do fence the tree off, with metal gates/panels. then the horses all stand and look, trying to figure out how to get an apple.
I graze my mini in my orchard however I only do that when there's no fruit for him to steal. Most of the year it's fine! I think Tami's suggestion of a muzzle is great. Muzzle him when the fruit is in season and the rest of the year you don't have to worry. However, there is another consideration. Minis don't need pasture 24/7 and giving him free access to grass will cause its own set of issues. My mini is a good weight and he's only allowed to eat 2 hours a day on pasture during peak grass season.
I keep my horses in a field with an apple tree and they do just fine. They rarely eat the fruit off the tree in the field, they prefer the apples off of our other tree for some reason. If you have good grass, your horse will likely prefer that, but I would watch for a couple days before taking any action to block him away from the tree that won't do any harm.
hi,great wrighting. i like to learn some thing when i read. i am 63 and just getting back to riding. i wish you had a for seniors only page.