FACTORS INFLUENCING CODLING MOTH LARVAL RESPONSE TO ALPHA-FARNESENE

Behavioral responses of newly-emerged codling moth (Cydia pomonella L. ) larvae to alpha-farnesene were compared for a laboratory-reared stra in ('lab', 160 generations inbred) and a recently collected strain ('w ild', 3 generations). Video recordings of single larvae placed 20 mm f rom Bond papers releasing a range of seven alpha-farnesene concentrati ons were scored for head turning, head lifting, head direction, and mo vement across a Petri dish. The laboratory strain was significantly le ss successful at finding the treated papers than the wild strain. The lab strain was also significantly less active, shown by more random or ientation, slower walking speed, less head turning and less head lifti ng. Both strains showed lower response to alpha-farnesene concentratio ns less than 10(-6) (w/v) alpha-farnesene. Orientation, walking speed, and head turning rate were significantly higher in the presence of al pha-farnesene concentrations > 10(-7) w/v, for both strains. Head lift ing did not show any effect from alpha-farnesene. Head turning was ass ociated with both head lifting and walking speed and this association improved with the presence of alpha-farnesene. Increased attraction to odour source was correlated with improved direction finding at concen trations above 10(-7) w/v. Activity factors such as head turning and w alking speed influenced time to locate odour source more than orientat ion factors. Odour-guided orientation to alpha-farnesene in codling mo th larvae was composed of both locomotory, and to a lesser extent, ori entation responses, which increased in a directed fashion to the stimu lus.