Sclerotinia lettuce drop (SLD),caused by Sclerotinia minor,is the most important disease of lettuce production in Victoria,Australia.Lettuce is also infected by S.sclerotiorum,but this pathogen is more prevalent in warmer humid climates and bean production regions of Australia.Both pathogens survive between susceptible crops as sclerotia in soil.In Victoria,lettuce is produced mostly with overhead irrigation in short rotations with Brassica and other minor vegetable crops.This production system has resulted in the build up of sclerotia in soils,causing high levels of disease and crop losses when weather conditions are favourable for infection.