Diapause induction in field populations of the codling moth,Cydia Pomonella,in Northern Israel

Diapause induction in field populations of the codling moth,Cydia pomonella L., was studied for three consecutive seasons (1984–86) in two commercial apple orchards in Upper Galilee. One orchard was located in the Hula Valley and the other in the high mountain region. The onset of diapause sometimes occurred during increasing day-length, before the summer solstice. This phenomenon represents a small proportion of the population which is probably genetically univoltine. The critical photoperiod which induces 50% diapause (= CPhP₅₀) varied up to 5 days within the valley region, up to 6 days within the mountain region, and up to 7 days between the two regions. The trend of this variation was consistent: the CPhP₅₀ of the valley poulation preceded that of the mountain on both ‘Jonathan’ and ‘Granny Smith’ apple varieties and, within each location, the CPhP₅₀ on the early-ripening ‘Jonathan’ preceded that of the late-ripening ‘Granny Smith’. The higher prediapause temperatures of the Hula Valley caused earlier diapause induction as compared with the lower temperatures of the mountain region. Immature fruits delayed diapause induction in comparison with mature ones.