Citrus peelminer generations occur every 580 degree days after the first flight in March.  The 3rd citrus peelminer flight that lays eggs on pummelos and grapefruit began the week of June 18.  We are now experiencing the 4th flight and in another 580 degree days the fifth flight will occur, which is the one that attacks susceptible orange varieties such as Fukumoto and Atwood.  For more info, see the degree days on the web page: http://ucanr.org/sites/KACCitrusEntomology/Home/Citrus_Peelminer/Degree_Day_Calculations/