Specificity of male response to multicomponent pheromones in noctuid moths Trichoplusia ni and Pseudoplusia includens.
The response of males of Trichoplusia ni and Pseudoplusia includens [Chrysodeixis includens] to the 6-component pheromone of T. ni, the 5-component pheromone of C. includens and the major component common to each pheromone, Z7-12:OAc [looplure] was studied in a flight tunnel and in soyabean, cabbage and broccoli fields in Louisiana in 1983-1985. Males of T. ni exhibited significantly greater levels of response to the 6-component blend than to looplure alone. A low level of cross-attraction of males of this species to the C. includens pheromone was observed which was similar to the response to Z7-12OAc alone. In the flight tunnel, males of C. includens exhibited a greater level of response to the 5-component blend than to looplure alone, but in the field these responses were not significantly different. There was a low level of cross-attraction of males of C. includens to the 6-component blend, but this appeared to involve a significant arrestment effect on the upwind flight of males, as well as a difference in male sensitivity to the blend of components compared with looplure alone. The arrestment effect may be due to male perception of one or more minor components of the T. ni pheromone. It is concluded that multicomponent pheromones of these species function effectively as specific mating signals and that discrimination of odour quality by males can occur as the result of minor components affecting male sensitivity or their upwind flight response to the pheromone.