Synthetic sex pheromone of the pea mothCydia nigricana. (E,E)-8,10-dodecadien-1-yl acetate (E8,E10-12 : Ac), was applied in a 3-ha pea field at a rate of 17 g/ha, in two different dispenser formulations. Aerial concentrations within pea canopy, as determined by a field electroantennogram (EAG) apparatus, were 2 and 3 ng/m(3) in the two dispenser treatments. The validity of the EAG measurements was corroborated by sampling of field air, followed by gas chromatographic quantification ofE8,E10-12 : Ac. Males were attracted to fresh dispensers releasingE8,E10-12 : Ac plus less than 2% of the antagonisticE, Z; Z, E; andZ, Z isomers. Two days after placement, the proportion of these isomers had increased to 6%. Males were then no longer attracted to the dispensers, but were observed to fly out of the treated field. Male attraction to calling females was almost entirely suppressed, and attraction to traps baited with synthetic pheromone was significantly reduced. Larval infestation in the pheromone-treated field was 2%, compared to 36% in a control field.