Chickens under fruit trees

So I decided to run the chickens under my fruit trees this year to get an bug larvae. Problem, they are digging so far down that its exposing some roots. My trees have only been in our ground for a few years and are probably 4-5 years old. Any advice? I thought well maybe its just time to move them, but I want to make sure they get all the bad bugs like the codling moth. Thanks for any help!

It's not advised to let chickens enter a system until it's established, and you have a lot of options. You can tractor them and move them around so they don't scratch too much, paddock them for the same strategy, or you might be able to lay down cardboard and stones on top of that as a protective layer immediately around the trees. 4-5 yr old trees could have extensive roots though, how big are they?

The roots aren’t too extensive, the caliper is probably less than 2.5 inches. Im already rotating them through a paddock ala Paul Wheaton and they have only been in there for a few days. I have 4 hens. I laid some rocks over top which helps, but I thought the point of having them under the trees is to keep bugs down, and if they can’t get to the bugs then it kinda defeats the purpose or am I missing something? Thanks for your response.

Might just wanna wait a year then to let the trees get more established

I know it's not 'by the book' but I've been planning a way to get my birds in the orchard sooner than later as well- and I just know those hens are going to scratch up all my my beautiful mulch and asparagus/rhubarb/comfrey etc etc.
My most likely action will be to make chicken wire "collars" to lightly cover the mulched area. Nothing fancy, and somehow allow the herbs/plantings to poke through without being squashed. Poultry definitely find route of least resistance.

Ive done a bit of that too, its just impossible to tell if that is defeating the purpose or not. I guess we could do a control area and do protected vs not protected and see if those trees have issues or not.