The blackmargined aphid, Monellia caryella (Fitch), is an important phytophage in the pecan, Carya illinoinensis (Wangenh.) K. Koch, agroecosystem where it often is treated with insecticide. Pecan cultivars released by the USDA Pecan Breeding Program vary in susceptibility and risk of damage from the blackmargined aphid. We evaluated a new technique that measures honeydew deposition and found relative differences in susceptibility of a segregating pecan population were identifiable during the course of an outbreak of blackmargined aphids. This provided an efficient method for the simultaneous evaluation of hundreds of segregating pecan trees. Use of this new tool will also aid studies of inheritance, horticultural compatibility, and in determining the relative permanence of this character in pecan improvement.