Q: Why are the leaves of my peach tree so red and puckered? The fruit seems to be affected too.
A: This is peach leaf curl. It is a fungus that loves rainy spring weather. Best way to control it is with a garden fungicide that contains copper (click for sources). It is typically applied once in December and another time in February.
Affected leaves will usually fall off but new leaves that are infected will turn red as the summer progresses.
Once you have this disease, it is important to spray regularly. If you do not…..and you subsequently have a rainy spring…. your whole tree will be affected.