Epidemiological studies of false smut disease of rice (Ustilaginoidea virens) in Bihar

False smut or green smut, caused by Ustilaginoidea virens is an important emerging disease of rice in India causing 5-85 per cent yield losses in India and 15-50 percent losses in some rice growing districts of Bihar. This disease, not only reduces yield and quality of rice, but also produces large amount of mycotoxins. False smut of rice has great impact on cultivation of different rice varieties and date of sowing. In the present investigations, epidemiological studies were done on five different varieties viz., Sahbhagi, Abhishek, Sushak samrat, Sabour ardhajal and IR-64 and four date of sowing (15th June, 25th June, 05th July and 15th July) of rice during 2015-16. The maximum disease severity and incidence were occurred at temperature range of 32-24oC, relative humidity (88-74%), rainfall (6.67-6.66 mm) and sunshine hrs (6.20-6.29 hrs) both in case of variety Sabour ardhajal and 25th June sown crop whereas, minimum disease incidence and disease severity occurred when temperature and relative humidity was same but their sunshine hrs and rainfall was lower than both Sabour ardhajal and 25th June sown crop in case of Sahbhagi variety and 15th July sowing. It was also revealed that in case of yield, Sabour ardhajal had minimum 31.42 q/ha whereas maximum yield was found in Sushak samrat (42.22 q/ha) and early sowing 15th June sown crop had maximum yield (41.20 q/ha) and late sown 15th July crop had minimum yield of 36.93 q/ha.