Theoretical considerations indicate that radiational energy loss and air-leaf temperature depressions may be reduced by lowering canopy emissivity. Aluminum powder suspensions applied to the upper leaves of “Red Blush” grapefruit ( Citrus paradisi Macf.) trees reduced canopy emissivity (4–12%) and increased leaf temperature (0.6-0.9°C). Net radiation loss was reduced up to 9%. When net radiation loss was not reduced, air-leaf temperature depression reductions were greater.