Evaluation of some selected seed treatments against leaf blast, brown spot and narrow brown leaf spot diseases of hybrid rice

An investigation was carried out to evaluate the efficacy of some selected seed treatments on incidence and severity of major field diseases and yield contributing characters of imported hybrid aman rice (Taj-1) in the Seed Health Laboratory of the Department of Plant Pathology and the field of Sher-e-Bangla Agricultural University farm during the period from November 2009 to December 2010. Eleven seed treating agents viz. untreated control, sun drying, polythene solarization, brine solution, neem leaf extract, allamanda leaf extract, hot water treatment, Provax 200 (carboxin), Bavistin 50 WP (carbendazim), Dithane M 45 (mancozeb) and Trichoderma harzianum were evaluated against disease incidence and severity at three growth stages (flowering, milking, maturity) and on yield contributing characters in vivo. Three seed borne field diseases viz. brown spot (Bipolaris oryzae), narrow brown spot (Cercospora oryzae), leaf blast (Pyricularia grisea) were recorded and identified. The disease incidence and severity of brown spot at maturity stage were recorded from 5.48 to 13.89% and 0.91 to 1.67 (0-9 scale), respectively where Dithane M 45, Bavistin 50 WP and Provax 200 showed good performance against the disease. In case of leaf blast, the disease incidence and severity ranged from 5.96 to 16.11% and 2.63 to 5.86 (0-9 scale), respectively at maturity stage where hot water treatment showed the lowest incidence (5.96%) and severity (2.63). In case of narrow brown leaf spot, the disease incidence and severity ranged from 1.49 to 7.79% and 0.63 to 3.44 (0-9 scale), respectively at maturity stage where three fungicides and hot water treatment effectively managed the disease.The highest growth and yield contributing characters were recorded under the fungicidal seed treatment followed by hot water treatment considering plant height, panicle length, effective panicle and filled grain. Grain yield ranged from 7.27 t/ha to 10.40 t/ha where the highest grain yield (10.40 t/ha) was recorded under Dithane M 45 followed by Bavistin 50 WP and Provax 200. The lowest grain yield (7.27 t/ha) was found under polythene solarization which was statistically identical with untreated control. It was observed that disease incidence and severity was gradually increased from flowering stage to maturity stage with the age of the plant and minimum incidence and severity gave the maximum yield.