Pheromone studies often seek to identify an optimal response to continuously varied mixture components wherein proportionality of one component cannot be varied independently. Geometric designs allow systematic and efficient exploration of multi-dimensional experimental space. In the relatively simple case of the leafminer Phyllocnistis citrella, a pest of citrus worldwide, we examined the effect of proportionality and concentration on attraction and mating disruption using a geometric design that avoids conflation of proportion and amount. The result is identification of an optimal proportion of the two major components of the sex pheromone of P. citrella. Of greater interest is our finding that only a single pheromone component is required for optimal disruption. Our results support a non-competitive model for the mechanism of mating disruption in this species and suggest an highly efficient and appropriate experimental design for pheromone blend studies.