Temporal development of stem rot caused by Athelia rolfsii in peanut fields in Iran

Stem rot caused by Athelia rolfsii (syn. Sclerotium rolfsii), is an important disease of peanut in Iran. Soil samples were collected from 15 peanut fields before the 2014 growing season in Guilan province, Iran and the viable sclerotia were counted using the soil-tray technique. The 15 selected fields were also evaluated for disease incidence at three intervals during the growing seasons of 2013 and 2014. The disease incidence at the end of the growing season ranged from 0 to 29.3% and from 0 to 45% in 2013 and 2014, respectively, depending on the field. The disease progress model, which was introduced for each field based on the disease incidence, showed good fitness with the monomolecular model in both years, but especially in 2014. Disease severity was evaluated in three out of the 15 peanut fields at three intervals during the growing season of 2014. The monomolecular model could describe more than 88% of the data. There was a significant linear relationship between the disease incidence or severity at the end of the growing season and the inoculum density in the soil. A positive linear relationship was also observed between the disease progress rate and the inoculum density.