Attraction of male Pandemis limitata (Lepidoptera: Tortricidae) to natural and synthetic pheromone sources: importance for assessing communication disruption

Abstract

AbstractIn flight-tunnel assays in both clean and pheromone-permeated air, we compared attraction and behavioural responses of male Pandemis limitata (Robinson) to “calling” females, female pheromone gland extract (FGE), and synthetic sources of pheromone. In clean air, female-baited traps caught significantly more males than traps baited with rubber septa lures loaded with 10 or 100 µg of the known pheromone components ((Z)-11-tetradecenyl acetate (Z11-14:Ac) and (Z)-9-tetradecenyl acetate) blended in a 91:9 or 94:6 ratio. Traps baited with septa loaded with 500 µg of the 94:6 blend caught as many males as did female-baited traps. Proportions of males engaging in wing fanning, take-off flight, locking onto the plume, and upwind flight towards a rubber septum loaded with 100 or 500 µg of the 94:6 blend were not significantly different from proportions exhibiting these behaviours in response to calling females. Only 500 µg lures elicited as much source contact in the same time as did a calling female. In clean air, traps baited with FGE applied to filter paper at 5 or 10 female equivalents caught as many males as did calling females. In air treated with Z11-14:Ac applied as a pheromone disruptant, females attracted more males and did so sooner than did five equivalents of FGE on filter paper. Consequently, disruption of male orientation to calling females was significantly shorter (74 h) than disruption of orientation to FGE (146 h). However, FGE dispensed from a piezoelectric microsprayer at a rate equivalent to 50 pg of Z11-14:Ac·min–1 caught as many males as a calling female. At this delivery rate, two-choice microsprayer bioassays revealed that FGE containing the two known components at a 91:9 ratio was more attractive than a synthetic blend of these two pheromone components alone at the same ratio. In air permeated with Z11-14:Ac, disruption of orientation to this FGE lasted 74 h, equivalent to disruption of orientation to females. These results suggest the published two-component pheromone blend for P. limitata is likely incomplete, and in the absence of suitable synthetic attractants, we recommend use of calling females or FGE delivered using a microsprayer system for any laboratory examination of communication disruption in this species.