Stemphylium blight caused by the fungal pathogen Stemphylium botryosum is a lentil disease that has become more prominent in Saskatchewan in recent years. The disease is not well studied under our growing conditions, and information is sketchy on optimal conditions for serious outbreaks of stemphylium blight, yield loss and appropriate disease management strategies. The objectives of this 5-year project are to develop a protocol for the mass production of spores (conidia) of Stemphylium botryosum for the purpose of controlled inoculations; to conduct replicated field experiments to determine yield loss through stemphylium blight, using the tunnel system evaluated in the pilot study and the spore inoculum developed under (1); and to evaluate and optimize the use of tunnels and spore inoculation for resistance screening of lentil germplasm to stemphylium blight.