Older peach trees are probably not worth the effort of transplanting the way these need to be done when already leafed out- marginal even if fully dormant as by the time trees recover you could have a good sized young bearing tree that started right now from a whip.

I don't know the exact amount of a ball necessary, and that would depend on soil type anyway, but for trees leafed out you must move at least double the amount of soil than you would for a dormant tree from what I've seen.

Peach trees are pretty much junk trees by my reckoning and don't allow the arborist much control of form once they've gotten away from you as you can't put branches where you want them- they don't reliably bud out of old wood.

The pears might be worth moving but you will need a really big ball as pears are very difficult to transplant once they are that size- even when they are not in leaf. Their root structure is decidedly non-fibrous.

I have a large box store crab apple(Read here it was suppose to be a Granny Smith) that I want to move. I ran across the site listed below then did a search for this Virgina Tech professor who researched transplanting trees. Her name is Dr. Bonnie Appleton. Do a search on her name for her method.
I could not do it this year because of schedule but will do it next year.

Hope this helps.

Here is a link that might be useful: Transplanting trees

Rather than a hydraulic tree spade maybe an air spade is the answer. Its my understanding that with an air spade you can free up very fine roots from the soil.

Marcom:

Since I work at a large BB nursery, I can help you. We
dig 3" caliper trees with a 32" diameter rootball. 3.5" get 36" diameter rootball. 4" get a 40" diameter rootball.

It would have been best to dig while dormant. Yes it will help to dig a LARGER rootball than listed above to help compensate for the trees already being in leaf. Once dug
and moved, water the roots appropriately but be sure to mist
the foliage twice a day if hot out after transplanting. This will greatly reduce them from stressing out and burning off. We do this all the time when planting BB stock in the heat of the
summer (pre-dug in spring).

I have some apples in my orchard that were ball and burlapped at 3". I can assure you it will take about 3 years for them to fully recover. Baby them with water the
first year as needed until they get established.

I've seen plenty of BB'd trees dug in mid-summer of up to 6" caliber not skip a beat- this is the kind of work landscape contractors routinely do that have very high-end clientele. Also well funded arboretums. No misting no wilting of leaves as trees look untouched.

Trees needn't suffer any stress at all- but boy, the poor people who have to move all that soil do. Misting is for the nursery trade where trees must be moved long distances, I think, and taking enough soil to prevent stress would be prohibitively expensive. For the poster it would seem to be very good advice, however, given his unusual situation.

I've moved plenty of dormant 3" caliber apples bare root and they generally recover after a single season (if you remove all flowers and cut back spurs when necessary)- you get much more root going bare root. I've never liked what tree spades do to a root system and you can never take much root even when hand digging and bb-ing

Harvestman, when you transplant these 3" caliper apples, how do you go about digging them up and what length of root do you take?

I use a hooked cultivating fork and a solid steel spade with a long handle and I take all the root I can reasonably reach- a 15' diameter roots system of a dug up tree is possible. I no longer attempt this kind of work by myself- my Ecuadorian helper is powerful and closer to the ground. I've never owned or run a back hoe.

One year I tried doing this in a clay soil when a commercial orchard had sold its land and it just wasn't cost affective- way too much work. I ended up using a tree spade and after they were dug up I had them set back down in the hole. When I moved them I broke up the soil and transported them bare root and they did great. 3 to 3.5" caliber trees that lost most of their root but were pretty much recovered within 2 years. We cropped them from the second year.