Ian:

Looks like what is referred to as "Leaf Spot" or "Leaf Blight." Most often are fungal problems cured by application of a good fungicide. It is tough to give an exact diagnosis from a picture. Do you have an Agriculture Extension Office near you. They would be able to make specific reccomendations. Good luck with curing it. It may require several applications of fungicide.

Harry

Ian: I have the same problem. Have you found any fungicide that seems to work? Dave

Its actually not a fungus but bacterial spot, which there are no sprays you can apply to treat. Unfortunatly the Tropic beauty peach is not resistant to bacterial spot.

I have a Tropic Snow peach and Sun best nectarine, both of which are very resistant to bacterial spot. But for encouragement, last year my tropic snow did have some issues with the bacterial spot, and this year I have no problems.

It is a fungus better known as "rust", not bacterial spot. Bacterial spot are black dots and more towards the tip of the leaf and on the fruit.

The best treatment that I found is a soil drench using Dithane M-45. Mix 2 Tablespoons (1oz) to one gallon of water. To that mix you can also add water soluble fertilizer such as tomato 18-18-21 or 20-20-20 using the same amounts stated. Re-apply again in 10-days, then re-apply 10-days after that again. You can also spray the trunk, branches, and leaves with this mix.

The best document actually a Power Point presentation that shows all types of peach disease and how to treat them can be found here: http://www.imok.ufl.edu/misc_news/peach_field_day06/diseases_of_peach.ppt

Very informative pdf doc.
http://www.doacs.state.fl.us/pi/enpp/pathology/pathcirc/pp69.pdf

Here is a link that might be useful: Diseases of Peach in Central and South Florida

That is nitrogen deficiency, not a peach fungus. Look it up and you will see clear pictures of what you have described. I have had a home peach tree for 6 years now and have battled just about everything with success.