Where in the United States are you?
What is the soil the trees are growing on like? Nutrient levels, pH, organic matter, Calcium and Magnesium levels and balance?

Timing of controls is essential and without knowing where you are it is impossible to suggest anything.

you should visit the fruit forum and ask about IPM systems for your peach ...

integrated peach management.. is a year around program of spraying to prevent all pests ...

frankly ... unless you go the chemical route.. i doubt you will ever get a grocery store quality crop ...

and the avoidance of chems.. is why i quit growing fruit ...

very superficially ... you spray the tree while dormant ... nothing while flowering.. then spray the tiny fruit ... and then 2 or 3 times while developing ... and that is much more than i ever wanted to do ...

frankly.. by the time you buy all the sprays.. and count all your hours ... i can go to the local orchard and buy a bushel of fruit for half the cost ...

i am sure there are organic solutions ... but you still have multiple products [$$$] .. and multiple sprayings ... its just not worth it .. unless you have no other hobbies or responsibilities ...

and as noted.. TIMING is everything .. it is way too late.. by the time the fruit is an inch big ....

good luck

ken