Role of sex pheromone components in behavioral reproductive isolation between Autographa gamma (L.) and either Trichoplusia ni (Hubner) or Chrysodeixis chalcites (Esp.) (Lepidoptera: Noctuidae: Plusiinae)
1992
Mazor, M. | Dunkelblum, E.
The composition of the Autographa gamma sex pheromone was reexamined and only (Z)-7-dodecenyl acetate and (Z)-7-dodecenol were identified by capillary GC, GC-MS, and dimethyl disulfide derivatization and subsequent GC-MS analysis. The fatty acid content of the pheromone glands was also studied, and a series of saturated and unsaturated acids was identified. However, most of the related pheromonal compounds were not detected. The male response to the pheromone components was studied in a flight tunnel and compared with the response to calling females. The best synthetic baits evoked a response similar to that observed to the virgin females, but males spent significantly more time at calling females than at the synthetic baits. The preferred synthetic baits consisted of (Z)-7-dodecenyl acetate alone or of a blend with 5% (Z)-7-dodecenol. Increasing the relative amount of the alcohol caused a gradual reduction in male response, particularly in the last steps of the courtship sequence. The addition of the minor sex pheromone components of the sympatric Plusiinae species, Trichoplusia ni and Chrysodeixis chalcites, to the A. gamma pheromone was also investigated in the flight tunnel. Some of these components exhibited a significantly antagonistic effect on the A. gamma male courtship behavior. The most potent antagonists were (Z)-5-dodecenyl acetate and (Z)-9-tetradecenyl acetate. The response of A. gamma and T ni males to conspecific and heterospecific females was also compared in the flight tunnel. Whereas A. gamma males were attracted only to their conspecific females, a small percentage of T. ni males were also attracted to A. gamma females and 11% performed the whole courtship sequence.
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