Trapping experiments were conducted in orchards to test the hypothesis that exposure of the mullein bug,Campylomma verbasci (Meyer), to atmospheres permeated with its synthetic sex pheromone, a 94:6 blend of butyl butyrate (BB) and (E)-crotyl butyrate (CB), or BB or CB alone, would alter the pheromone responses of males toward off-ratio blends. Exposure to the natural 94:6 blend shifted the response preference away from the natural ratio to blends enriched in BB, including a 99:1 blend, which is normally significantly less attractive than the natural ratio. In an atmosphere permeated with CB, male mullein bugs were as responsive to blends containing 20, 33, and 43% CB, up to seven times the natural percentage, as they were to the 94:6 blend. In an atmosphere permeated with BB, responses to five blends ranging from 94:6 to 99:1 BB:CB were not significantly different, whereas in an untreated atmosphere blends of 98:2 and 99:1 were significantly less attractive than the 94:6 blend. Individual components appeared to disrupt pheromone communication primarily through the creation of a sensory imbalance and modified interpretation of pheromone blend ratios, whereas disruption by the complete pheromone blend apparently involves several mechanisms, including false-trail following and camouflage. Disruption of pheromone communication was most effective with the natural 94:6 sex pheromone blend.