Among the important fungal diseases affecting lettuce, lettuce drop caused by Sclerotinia spp., is one of the most common and destructive diseases resulting in yearly losses in all lettuce-producing regions for all types of lettuce (Wu and Subbarao, 2006: Phytopathology 96:1322-1329). Crop losses may vary from 1 % to nearly 75%, and in some cases, entire fields may be lost (Chitrampalam et al 2008. Plant Dis. 92:1625-1634). Repeated cultivation of lettuce and repeated occurrence of lettuce drop in Arizona and California results in increased accumulation of the lettuce drop pathogens in the soil and increased disease incidence on subsequent lettuce crops. Thus, improved management strategies for lettuce drop, including the development of non-chemical treatments, will have direct benefits to lettuce growers in both states.