Twenty-eight greenhouse screening materials, with predetermined airflow resistance values, were evaluated for exclusion of the silverleaf whitefly Bemisia argentifolii Perring & Bellows and thrips from a mixed-species population. Screens differed in exclusion efficacy, expressed as a percentage of the fiberglass window screen control and at an approach velocity of 92 m/min, from −35 to 94% for silverleaf whitefly and from −13 to 95% for thrips. Seventeen screens excluded more silverleaf whitefly than did the window screen control, whereas only seven excluded more thrips. One material differentially excluded whitefly over thrips; many more differentially excluded thrips over whitefly. Airflow resistance, indicative of mesh hole size, did not necessarily correspond with degree of exclusion. Not all materials characterized as highly resistant to airflow provided significant exclusion. Exclusion of both types of pests was attained with several moderate- and one low-resistance screen. Another low-resistance screen excluded silverleaf whitefly only.