Regional variation in pheromone-mediated behaviors in grape berry moth

Substantial regional variation exists in the magnitude of the response of male grape berry moth Paralobesia viteana (Clemens), to sex pheromone baited traps in Michigan vineyards. Males are readily captured in traps in the southwest region, whereas in the northwest very few, if any, males are captured. Despite this, in both regions grape berry moth larval infestation is found in fruit. To determine whether these differences are driven by variation in pheromone-mediated behavioral responses, we determined the response of male moths from north and south populations to the pheromone blend used in monitoring lures and to females from the same or the different region. In Y-tube choice tests, males from southwest Michigan were more likely to orient toward the standard pheromone blend than were males from northwest Michigan. Additional Y-tube experiments to compare the response of males to females from the same or different region suggest a preference for females of the same population. In addition, we are using captive female traps in the field to test the preference of males for females from the same or different regions, as well as for the standard pheromone lure. We postulate that males will preferentially choose females from the same population, and there will be regional variation in response to the pheromone lure, with implications for monitoring and mating disruption of this pest.