Technical Abstract: Aphids cause major annual economic losses to the U.S. pecan [Carya illinoeninsis (Wangenh.) K. Koch] industry and are becoming harder to control. This study reports on a novel means of controlling aphids using Silwet L-77, a non-ionic super-wetting organosilicone surfactant. Evaluation of the strategy being adopted by certain growers of using air-blast sprays of 0.05 percent Silwet L-77 indicated; a) that reductions in blackmargined aphid [Monellia caryella (Fitch)] levels were mostly attributable to the air-blast spray effect rather than to the Silwet L-77 component, b) that the 0.05 percent solution reduced net photosynthesis ('A') of foliage about 5 percent for at least 14 days post-treatment, and c) that the efficacy of 0.05 percent sprays is not increased by doubling the volume of spray per tree. Conversely, a concentration response curve indicated that air-blast sprays of orchard trees with a 0.30 per cent (v/v) solution of Silwet L-77 would be expected to reduce yellow pecan aphid (Monelliopsis pecanis Bissell) populations by about 84 percent while minimizing its adverse side-effect on ('A') to less than or equal to 10 percent suppression for periods up to at least 14 days post-treatment. Chemical names used: silicone-polyether.