Disruption of orientation ofEuxoa messoriamale moths to traps baited with a synthetic sex attractant or virgin females was studied under two field designs. In both designs, the atmosphere in the test sites was permeated with (Z)-11-hexadecenyl acetate (Z11–16:Ac), (Z)-7-hexadecenyl acetate (Z7–16:Ac), and (Z)-9-hexadecenyl acetate (Z9–16:Ac), each compound singly or as a ternary blend. In 81-m2test plots, effective (>89%) disorientation of males occurred, using the blend or Z11–16:Ac alone; Z7–16:Ac and Z9–16:Ac, tested singly, were ineffective. In the other test sites, where the disruptants were released from rubber septa in close proximity to the monitoring trap, disorientation resulted from both the blend and Z7–16:Ac alone; Z11–16:Ac was ineffective under these conditions. Studies of male behavioral responses to these components in a flight tunnel showed that Z11–16:Ac is a long-range attractant whereas Z7–16:Ac primarily effects close-range flight and landing. No behavioral effect could be attributed to Z9–16:Ac. Results of flight tunnel responses and visual observations of field test sites accounted for the disruption results obtained.