State of sheath blight in the rice fields of Mazandaran province

Sheath blight, caused by Rhizoctonia solani AG1-IA, is an important disease of rice in Northern provinces of Iran, including Mazandaran. In order to study the status of the disease in the province, 53 fields in 5 regions (Amol, Sari, Qaemshahr, Savadkuh and Behshahr) were evaluated during 2008 and 2009 seasons. Statistical analyses of disease data were performed based on disease incidence (I), mean severity (S), (Lesion height / plant height) and (S2), (Number of diseased tillers / number of tillers in a diseased hill) of the fields. The results revealed that the regions were significantly different based on the I, S and S2 (P<0.01). Minimum and maximum of disease amounts were observed in Behshahr (with I, S and S2 values of 10.92, 6.55 and 9.9 %,) and in Amol (with I, S and S2 values of 42.87, 28.66 and 34.99 %,) respectively.