Sunlight, particularly from the ultraviolet (u.v.) spectrum, may have a great impact on the survival and longevity of any microbial antagonist deposited on the stems and leaves of rice plants (Elc¸in and Okterner 1994). As a consequence, one of the features required for an effective biological control product is to possess the capacity to withstand the detrimental effect of exposure to u.v. This feature is particularly required if the product is aimed for use as a foliar spray to control sheath blight disease when the disease occurs during the tiller stage of rice growth. U.V. protectant compounds, such as lignin (PC 1307) and Blankophor BBH, have been demonstrated to protect Bacillus subtilis strain OH 131.1, an antagonist that is effective in reducing Fusarium head blight disease of wheat, against u.v. light produced from artificial sunlight (Schisler et al. 2004).