Bionomics of Codling Moth

Ecological Adaptations

The ecological features of the life cycle of the codling moth reflect adaptation to the seasonal nature of the temperature, latitude, and climate in which there is alternation of warm and cold periods of the year. Its life cycle is regulated by temperature adaptions of the active and diapausing stages and by the photoperiodic reactions that synchronize development with the seasonal rhythm of the climate and with the fruiting of the apple

Adaption of the life cycle o the codling moth to the seasonal rhythm of the climate and the periodicity in the fruiting of the apple is maintained by the geographical variability of its photoperiodic reaction. The temperature reactions of the active stages and cold resistance remain permanent specific attributes and are not subject to variability (Riedl, 1983).

Shel'Deshova (1965) reported that diapause termination was more uniform in the northern than in the southern populations. In southern areas the chill requirements for diapause termination may not get satisfied in all individuals of a population and their development would not resume under the short day lengths of early spring even if temperature was favorable. However, the longer day lengths and high temperatures later in the season provide an alternative mechanism to eventually terminate diapause in those individuals which received inadequate chilling and thus ensure their emergence the same year. The apple tree also requires a minimum duration of chilling, about 1,000 to 1,600 hours below 7°C, for reactivation in the spring (Westwood, 1978). Its reaction to inadequate chilling expresses itself as increased variability in bud development and an extended bloom period resulting in a fruit crop in various stages of maturity. Therefore, an extended emergence period of the overwintering generation in areas with mild winters could be advantageous to the codling moth in terms of synchronization with fruit development.

To sum up, in its ecological need, the codling moth is similar to the apple. The northern range of both species is determined by lack of heat and cold resistance, and the southern range by the need for a period of dormancy at reduced temperatures. The adaptive potential of the codling moth is restricted by the fact that it must adapt to the seasonal nature of the fruits of the apple as well as to the climatic rhythm.