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  • J.D. Sweeney (a1) and J.A. McLean (a1)


Western spruce budworm, Choristoneura occidentalis Freeman, adult males were observed in a wind tunnel for their response to synthetic sex pheromone and subsequently examined to determine their degree of infection with a microsporidian parasite, Nosema sp. A subsample of C. occidentalis was randomly selected and electroantennograms (EAG) of individual moths were measured for response to pheromone. The Nosema infection level ranged from 0 to 21.8 × 106 spores per milligram and was significantly negatively correlated with the proportion of males wing-fanning, taking off, and flying upwind to contact the pheromone source. The level of Nosema infection and the amplitude of the antennal response (EAG) to pheromone were not significantly related. These results suggest that Nosema affects the response of C. occidentalis males to pheromone in some way other than directly reducing the sensitivity of the antennae. We hypothesize that sublethal infections of Nosema sp. may reduce mating success of the western spruce budworm in field populations.

La réponse des mâles de la tordeuse occidentale de l’épinette Choristoneura occidentalis Freeman à une phéromone sexuelle synthétique a été suivie dans un tunnel aérodynamique afin de déterminer leur degré d’infection par un parasite microsporidien, Nosema sp. Un sous-échantillon de C. occidentalis a été choisi au hasard et des mesures d’électroantennogrammes (EAG) individuels ont été faites pour établir la réponse des papillons à la phéromone. Le niveau d’infection par Nosema a varié de 0 à 21,8 × 106 spores par mg; il s’est avéré inversement corrélé avec la proportion des mâles qui vibraient des ailes, prenaient leur envol et volaient à contre-courant vers la source de phéromone. Le niveau d’infection par Nosema et l’amplitude de la réponse antennaire (EAG) à la phéromone n’étaient pas significativement liés. Ces résultats indiquent que Nosema affecte la réponse des mâles de C. occidentalis à la phéromone sans directement réduire la sensibilité de l’antenne. Nous proposons que des infections sublétales par Nosema sp. peuvent réduire l’incidence d’accouplement dans les populations naturelles de la tordeuse occidentale de l’épinette.



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  • J.D. Sweeney (a1) and J.A. McLean (a1)


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