TRAPPING AND SEX PHEROMONE-MEDIATED FLIGHT AND LANDING BEHAVIOR OF MALE CTENOPSEUSTIS-OBLIQUANA

A sex pheromone-baited delta trap was found to be inefficient at elici ting landing and entering of the trap by male Ctenopseustis obliquana. The inefficiency of the delta trap related to turbulence altering the pheromone plume and the concomitant effect on the flight manoeuvres o f male moths. In the wind tunnel, high proportions of males flew upwin d and landed on the sides, outside, of the trap, but only a relatively small proportion of these males entered the trap and contacted the st icky surface. When males approached the delta trap, they tended to fly in wide zigzags (i.e., large inter-track reversal distances) and at a n altitude near the top of the trap, where the trap was relatively nar row in width (compared to the bottom). Thus, these flight manoeuvres l argely precluded males from entering the trap. Greater numbers of male moths entered the trap when: (i) the front barriers of the delta trap were removed, (ii) pheromone dosage was increased to 300 g mu, and (i ii) the trap design was changed to a rectangular one. The first two ch anges appeared to influence the flight manoeuvres of males (who appear ed to fly with narrower inter-track reversal distances), while the thi rd change apparently did not affect the flight manoeuvres of males, bu t rather allowed more males to enter the trap because of the greater a rea of the entrance. The low trap catches of male C. obliquana in the field are also a consequence of the glue which is currently used. Afte r contact with this glue most males are able to escape, flying off the sticky surface and losing contact with the pheromone. A field trial f ound that delta traps with another glue caught more than three times t he number of males of the related tortricid moth, Epiphyas postvittana , than delta traps with the currently used glue.