Nah. Probably a little water stress, exacerbated by lack of aggressive fruit thinning. You live in an area relatively well-suited for peaches which means you will have a huge set of fruit. AGGRESSIVELY thin those fruitlets. Sooner, rather than later. If its hard for you, do it in stages. Get a friend to do it while you have your back turned if you have to.

Go through as soon as the fruitlets are noticeable, say half the size of a pea and instantly pull off any that look a little misshappen or otherwise "off" strive to get them maybe 3" apart. Come through a couple of weeks later and thin to at least the width of your knuckle. Two knuckle widths is much better. Again, err on the side of aggressive thinning. The key word here is "ruthless"

P.S. Its enough of a project to grow peaches that you might as well get a named cultivar to grow. I'm not suggesting you uproot your science experiment, necessarily, but plant a well-suited tree for your area from a reputable nursery, so you'll have a "real" tree with quality fruit for your efforts.

Generally grafted works better, but this tree from seed should be from the domestic part of a grafted tree. Besides above comment you may want to prune the tree back.

It sounds to me like something else is going on with cmcqueen's tree, other than excessive fruit load. I can't imagine allowing the tree to over-set would cause all the fruit to drop off at dime size.

Cmc, Have you closely examined any of the fallen fruit? Have you noticed any insect scars on the fruit? I've heard of one plum curculio infestation bad enough to cause 100% loss.

It is possible that there were some weird genetics expressed in the peach seed, leading to an excessively small fruit that is even smaller due to lack of fruit thinning, but that still doesn't explain why all the fruit is dropping. My bet's on plum curculio.

I agree with the other posters that grafted trees are worth the cost, and fruit thinning is a necessary practice.

We have what seems to be the same problem with a Stanley plum. They would get to pea size, turn yellow and fall off. We assumed it was lack of pollination, so we took a wild plum branch with blossoms and tried that and still no luck. Last year we got a few more plum trees and will see if that helps. I'm interested in these responses though.
Jake

If the tree was a seedling of a parent that performs well in your climate your odds would be pretty good that you'd get decent peaches but if the fruit came from CA or some other much milder climate all bets are off.

cmcqueen: over how long a period of time did the peaches drop? Also, Did the tree also begin to drop leaves in addition to the fruit? I was caught alst spring with 2 surprises.

1) Shortly after the tree was fully leafed out it began dropping leaves, a week after the onset of leaves dropping I checked the soil moisture by takinging several soil cores with my soil sampling probe down to one foot at the drip line and found the soil to be bone dry. I watered thoroughly and that stopped the leaf drop.

2) When the fruit were about the size of quarters they started falling off at about 7 - 10 per day and continued to do so for about 6 weeks. See the picture below for what they looked like when they fell off. The best I could come up with, based on the hole in my spray schedule at a critical time and the weather conditions throughout the bloom period, was Green Fruit Rot. The fruit were thinned prior to the onset of the mass drop due to GFR to a distance of about 6-8" between fruit on the limbs.

That's my 2-cents worth.

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Berry nut
I don't think a wild plum will pollinate a Stanley plum. I think you need another European plum as a pollinator