Abstract
Sheath blight caused by Rhizoctonia solani is a major disease of rice in Bangladesh. Experiments were conducted during the period of 2010-2013 to develop management strategy for the disease. The effect of removal of debris prior to transplanting, time of planting, evaluation of fungicides, nutrients and their integration on the incidence and severity of sheath blight of rice were assessed. CRD for the laboratory and RCBD for the field experiments were used. The highest percent hill infection was found in control plot (Floating debris not removed) than that of FDR (Floating debris removed) plots. The debris floating on the irrigation water in the field had significant impact on the development of sheath blight disease. Disease severity was the minimum when transplanting was done in 30 July but it was the highest in 15 August transplanting. The minimum hill infection was noticed in four splits of application of urea, but the maximum hill infection was recorded when whole amount of urea was applied at a time. Two and three splits of urea application also had significant impact on hill infection. Sheath blight development was higher in absence of potash fertilizer in case of standard fertilizer dose (187:30:0:24:4 gm NPKSZn/decimal) followed by standard fertilizer dose (187:30:101:24:4 gm NPKSZn/decimal) plot. Standard fertilizer dose with 60% additional potash (187:30:162:24:4 gm NPKSZn/decimal) significantly reduced the disease, however, the best control was obtained at double dose of potash. This treatment also increased the grain yield significantly. Out of 57 local germplasms, Orgoja showed resistance and Gopalgosh, Dorkumur, Kalagora, Binni showed moderately tolerant reaction to sheath blight both in the field. The germplasms tested by detached sheath inoculation method in test tube, Gopalgosh showed the moderately tolerance and Orgoja showed resistance reaction. Fungicides namely Azoxystrobin, Tebuconazole, Carbendazim, Nativo and Cabriotop were tested at the concentrations of 0.25, 0.5, 1.0, 10.0 and 100μg/ml. 100% inhibition was observed for Nativo and Tebuconazole and 85% for Azoxystrobin when 100 μg/ml was used. No growth was observed at 10μg/ml of a.i. of the fungicide combination (Azoxystrobin 20% + Tebuconazole 80%). Tebuconazole was the best fungicide to prevent lesion height produced by Rhizoctonia solani. Azoxystrobin was able to limit RLH within 30.25% in comparison to 72.75% in the control plots (no fungicide). The maximum grain yield was 5.18 t/ha in case of using Azoxystrobin 10% + Tebuconazole 90% treated plot, whereas it was 3.21 t/ha in diseased plots. RLH, DI, tiller infection and hill infection were maximum in control plot and minimum in the plots of integrated management (FDR + 30 July transplanting + double dose of K + Four splits of urea + Two spray of fungicide) of sheath blight disease. Finally, research along with advanced techniques should be involved to develop high yielding varieties against sheath blight of rice. Integrated package shall be simulated in the farmer's fields in different AEZ and seasons with different varieties.