A program of mass-trapping for control of 6 tortricid pest species of apple demonstrated relationships between trap catch and an index of apple foliage volume.Analysis of the trap catch data obtained from trap station densities ranging from 4 to 17 stations/acre revealed significant correlations between number of male moths caught and the amount of foliage/acre forArgyrotaenia velutinana(Walker),Choristoneura rosaceana(Harris),Grapholitha molesta(Busck), andGrapholitha prunivora(Walsh). The correlation was not significant forPandemis limitata(Robinson). Where the trap catch of the tortricids did not correlate significantly with foliage volume, the correlation between catch and trap density suggested that pheromone trap efficacy was decreased by a lack of effective drawing range, density of the foliage, competition by calling females, or some interaction of these factors. In the case ofLaspeyresia pomonella(L.), which was established in a gradient across the orchard, significant correlations between population density, foliage volume, and trap density were not evident.