The success of cross-strain mating in plum curculio, Conotrachelus nenuphar (Herbst), was studied in summer, 2004. Plum curculio populations originating in four states were used in the experiment, including two northern strains: New York and Virginia, and two southern strains: West Virginia and Florida. This is a reciprocal cross experiment to evaluate the success of cross-strain mating. There are two factors (maternal origin, paternal origin) arranged as a 4x4 factorial: four levels within each factor: New York, Virginia, West Virginia, and Florida. Reproductive incompatibility in the cross-strain matings was shown between following combinations: New York and Florida, Virginia and Florida, New York and West Virginia, Virginia and West Virginia. Within-strain mating (New York and Virginia, West Virginia and Florida) were reproductively compatibile.