Petroleum spray oils (PSOs) have been used for control of a wide range of pests and are now an essential part of many integrated pest management programs (IPM) for agricultural and horticultural crops (Simanton and Trommel1966, Riehl 1981, Johnson 1985, Lee et al. 1991, Beattie 1995, 1997, Rae et al. 1996, 1997). PSOs have little impact on natural enemies of crop pests and therefore can complement the activity of beneficial insects in crop systems. However, the use of PSOs in the cotton industry is limited due to the risk of PSO induced phytotoxicity which is related to the high molecular weight of the oils (Riehl 1969). Recent research on citrus and a range of other horticultural crops has led to the development of new technology in UV light protectants, which reduce the risk of damage to plants.