Factors influencing codling moth larval response to α‐farnesene

Behavioral responses of newly‐emerged codling moth (Cydia pomonella L.) larvae to α‐farnesene were compared for a laboratory‐reared strain (‘lab’, 160 generations inbred) and a recently collected strain (‘wild’, 3 generations). Video recordings of single larvae placed 20 mm from Bond papers releasing a range of seven α‐farnesene concentrations were scored for head turning, head lifting, head direction, and movement across a Petri dish. The laboratory strain was significantly less successful at finding the treated papers than the wild strain. The lab strain was also significantly less active, shown by more random orientation, slower walking speed, less head turning and less head lifting. Both strains showed lower response to α‐farnesene concentrations less than 10−6 (w/v) α‐farnesene. Orientation, walking speed, and head turning rate were significantly higher in the presence of α‐farnesene concentrations > 10−7 w/v, for both strains. Head lifting did not show any effect from α‐farnesene. Head turning was associated with both head lifting and walking speed and this association improved with the presence of α‐farnesene. Increased attraction to odour source was correlated with improved direction finding at concentrations above 10−7 w/v. Activity factors such as head turning and walking speed influenced time to locate odour source more than orientation factors. Odour‐guided orientation to α‐farnesene in codling moth larvae was composed of both locomotory, and to a lesser extent, orientation responses, which increased in a directed fashion to the stimulus.