The pheromone (cis-7,8-epoxy-2-methyloctadecane, named disparlure) ofPorthetria dispar(L.), the precursor olefin (2-methyl-cis-7-octadecene) and a combination of both chemicals were released into 0.01-ha field plots in a spaced release station atmospheric permeation technique. Disparlure and the combination were more effective than the olefin in suppressing catches of disparlure-baited traps located in the disruptant arrays. Behavioral observations and comparisons of catches of disparlure-baited traps located 40 m outside the disruptant release area with check traps suggested that both disparlure and the olefin elevated the number of males searching within and at the periphery of the arrays. Males terminating search behavior in the olefin array generally flew out at a height of 2 m or less; only 15% departed by flying up and out through the tree canopy. In the disparlure array 86% departed through the canopy.