Modelling the phenology of codling moth: Influence of habitat and thermoregulation

This study used an explorative, individual-based model to evaluate the influences of (1) plant architecture, i.e. dwarf versus standard trees, (2) the use of hail nets, and (3) insect behaviour on the phenology of the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), a major pest in apple orchards worldwide. Body temperatures of the different codling moth stages were approximated by microhabitat temperatures, behavioural response to temperature, and biophysically modelled temperature increments due to absorption of solar radiation. Results indicate a significant influence of habitat parameters on the phenology of the codling moth. Under the simulated conditions, adults appeared up to 6 days earlier in dwarf trees than in standard trees, and up to 5 days later in trees covered with hail nets than in trees without them. In contrast, thermoregulation behaviour, which is documented for the larval and adult stages, appeared to be of relatively low influence on the insect's overall phenology. Model validation using reported pheromone trap catches of male moths agreed with the simulated appearance dates of adults of the overwintered generation. Simulated and observed appearance dates did not deviate when habitat temperature was used, but deviated considerably when standard air temperature was used as driving variable. Considering habitat and behaviour will help to improve current phenology models for the codling moth.