Peacock Spot on olive trees is world wide and State wide here in California.Spores are spread by wind and rain so fall, winter and spring be aware of moisture conditions in the orchard.You will see the symptoms very easily in the spring and summer.Spots will appear on the leaves ranging in size from 1/16 to 1/2 inch. and eventually will defoliate branches.I see the disease in my Arbequina and luckily none in the Arbosana and Koroneiki, those varieties are resistant.
Cerospora leaf spot does not spot, contradicting its name.The spores do accumulate under the leaf.You will see leaf yellowing and defoliation.
We cannot control Fog or heavy dew in the orchards during the winter, but be mindful that sprinkler irrigation into canopies during fall,spring and winter this is an important factor.
The control is the same for both mold spores.Copper,Bordaux and copper sprays applied post harvest and spring.Important for orchard control to make sure that applications of copper are consistent.