I have two peach trees in my backyard here in Las Vegas, NV. One of them
had its fruit ripen earlier than the other and had no fruit quality
problems. My second and bigger peach tree is now getting ripe fruit.
This fruit is bigger. However, about 60 percent of the fruit is rotten.
I estimate about 60 percent of the fruit is affected. There are
various sized external "rot holes or just surface indications of it
being rotten. The fruit is soft and very mushy inside and is an off
color inside. Any ideas as to what is causing this?

Jerry

Here is a link to pictures of some bad peaches of this tree:

http://members.cox.net/jcjacques/peach/badpeach.html