Impact of Temperatures on the Voltinism of Cydia pomonella (Lepidoptera: Tortricidae)

Cydia pomonella (L.) is a worldwide dreadful pest in apple fruit production. In Morocco, where high temperatures are prevailing in a growing season, sexual traps demonstrate a massive flight of codling moth leading to an intensive chemical control. In Morocco, data concerning its life cycle are imprecise. Thus, its voltinism and the impact of temperatures on the progress of its generations were investigated during six growing seasons (2010-2015) in a Moroccan apple orchard. The degree days method was also investigated to verify the adaptability of codling moth populations to phenological models. Results revealed that codling moth flight consisted on three generations per year, whereas an additional fourth generation of moths is expected when the beginning of the life cycle (first generation) matches with high temperatures. The present study highlighted the importance of the first generation on codling moth control, as it represented around 50% of captures per year. The accumulation of an average of 360 degree days during April and May allowed an earlier and faster development of the first generation, which impacted the progress of the following generations, extended the presence of the insect, and consequently increased its voltinism. Moreover, temperatures during the period conducive to insect diapause (July to early August) are always high in Moroccan conditions and thus inhibit insect diapause. Finally, the estimated generations, based on degree days method, were in concordance with codling moth flight dynamics based on sexual traps captures, making possible the prediction of insect development pattern using a phenological model.