Spraying citrus (lime; Citrus auranticola (Christm.) Swing.) plants with clay suspensions containing kaolin or mixtures of kaolin and bentonite (montrorillonite) markedly reduced the rate of natural colonization by winged spiraea aphids (Aphis citricola van der Goot). The reduced colonization seems to be caused by the white coating of clay deposited on the leaves. Bentonite increases the adhesion of the clay suspensions on the leaves. These results suggest that clay suspensions may provide an ecologically acceptable control method for aphids, particularly under dry conditions.