Defining a synthetic pheromone blend attractive to male Heliothis subflexa under wind tunnel conditions

Heliothis subflexa males were flown in a wind tunnel to a variety of combinations of synthetic pheromone components admixed (on a filter paper disk. Blends containing (Z)-l1-hexadecenal (Z11-16:Ald, 1000 ng), (Z)-9-hexadecenal (Z9-16:Ald, 500 ng) and (Z)-11-hexadecenol (Z11-16:OH, 10-500 ng) elicited upwind flight and source contact in 52-69% of males. All these compounds have previously been isolated and identified from female H. subflexa gland extracts and volatile pheromone emissions. Males were not attracted by blends in which Z9-16:Ald was omitted (0% source contact). Similarly, blends lacking Z11-16:OH were unattractive to male H. subflexa (39% or less source contact). Males were extremely sensitive to the presence of Z11-16:OH; ever, responding in high numbers (57-69% source contact) to blends containing a dosage of 1% (10 ng) or greater Z11-16:OH. Males were unresponsive to blends in which Z9-16:Ald was replaced with a variety of dosages of (Z)-9tetradecenal, a secondary component of a closely-related congeneric species, Heliothis virescens. Another compound present in the blend emitted by con-specific females, (Z)-11-hexadecenyl acetate (Z11-16:Ac), did not inhibit H. subflexa males (69% source contact) when added to the three-component mixture (1:0.5:0.1) at a ratio of 0.1 (100 ng) with respect to Z11-16:Ald. These results indicate that Z9-16:Ald and Z11-16:OH are required in addition to Z11-16:Ald to elicit significant levels of upwind flight in H. subflexa males. The effects of Z11-16:Ac are more subtle, but at the dosage tested in these experiments, this compound does not have an antagonistic effect on upwind flight and source location by H. subflexa males.