The population dynamics ofLaspeyresia pomonella(L.) from an abandoned apple orchard and a commercial orchard located in the Yakima Valley of Washington are compared. There was a greater catch of overwintering moths in the abandoned orchard than 1st brood moths, which is just opposite to the situation found in the commercial orchard. Also, approximately 75% of the 1st brood larvae in the abandoned orchard go into diapause, whereas approximately 10% of the 1st brood larvae in a commercial orchard diapause. The principal explanation for the difference in diapause structure between a commercial orchard and an abandoned orchard seems to be a limited food supply in the latter. AlthoughAgathis nucicola(Muesebeck),Ascogaster quadridentataWesmael andGoniozussp. were identified as larval parasites of the codling moth, they did not seem to be a very significant regulatory factor. On the other hand, the egg parasite,Trichogramma minutumRiley, parasitized at least 50% of the eggs deposited by the 1st brood moths. Lack of late season larval food and a high level of late season parasitism appear to explain the selection of a univoltine component when orchards are released from insecticidal pressures.