Garlic white rot caused by Sclerotium cepivorum and its managing by soil solarization in Zanjan province, northwest Iran

White rot disease on garlic as a main agricultural problem was studied in Zanjan province, northwest Iran during 2008 to 2010. Garlic fields in studied areas were visited and infected samples showing foliage wilting, bulb rot were collected and transferred to the laboratory. Samples were cultured in PDA as a common medium after surface sterilization and Sclerotium cepivorum was identified as the most constantly faced pathogen. The disease caused garlic yield losses up to 65% in the growing locations which was the most economical problem for growers. Propagule of the pathogen was high in the field cropped to garlic for many years. Application of soil solarization reduced population density of the pathogen from 1200 to 100 CFU/g soil in treated fields. It was the reduction to undetectable levels of S. cepivorum in the upper 10 cm layer of soil, even in heavily infested soils, after solarization for 6 weeks. Rates of disease progress and final incidence of dead plants was greatly reduced in solarized plots. Yield production was about 75-125% over the unsolarized control plots in some locations.