Seconds-long preexposures to pheromone from rubber septum or polyethelene tube dispensers alters subsequent behavioral responses of male Grapholita molesta (Lepidoptera: Tortricidae) in a sustained-flight tunnel

Male Oriental fruit moths, Grapholita molesta (Busck), were briefly preexposed in a wind tunnel to plumes from a rubber septum lure releasing a three-component, optimally attractive pheromone blend for this species or to plumes generated by Isomate-M Rosso pheromone dispensers. The objectives were to determine how brief preexposures to low- and high-dosage pheromone dispensers affect initiation of anemotaxis, duration of sustained anemotactic flight, and peripheral sensitivity 15 min and 24 h after exposure. A greater proportion of G. molesta males took flight and successfully oriented toward a lure 15 min after briefly orienting in plumes generated by an identical lure compared with unexposed, naive moths or control moths preexposed to clean air. In addition, the proportion of males contacting a lure or orienting to the lure without source contact 24 h after a preexposure was not significantly different from the proportions of naive or control moths completing these behaviors. However, the mean duration of sustained flights of lure-preexposed male G. molesta in plumes generated by a lure was significantly shorter 15 min and 24 h after preexposure compared with that of naive moths. The proportion of male G. molesta contacting lures 15 min and 24 h after preexposure to ropes was not statistically different from the proportions of naive or control moths contacting the lure or orienting without source contact. However, as observed with moths preexposed to a lure, the mean duration of sustained flights of male G. molesta preexposed to an Isomate-M Rosso dispenser was significantly shorter than that of naive moths 15 min and 24 h after preexposure. Mean durations of sustained flights of male G. molesta preexposed to a lure or rope were significantly longer after 24 h compared with 15 min after the exposure treatment, indicating that the effect of pheromone preexposure decayed over time. Electroantennograms recorded 15 min and 24 h after preexposures to lures or Isomate-M Rosso dispensers in the flight tunnel were indistinguishable from those recorded from unexposed moths. We suggest that false-plume following by naive male G. molesta combined with decreases in duration of subsequent anemotactic orientations after previous bouts of false-plume following may explain why Isomate-M Rosso dispensers are effective in mating disruption experiments with G. molesta.