To study the effect of bacterial leaf blight on rice (Xanthomonas oryzae pv oryzae) yield in natural condition were conducted at the Agriculture Research Institute, Patna during the two consecutive years 2013 and 2014. Results were analyzed in both constitutive years with respect of four different plantation dates i.e., 9th June, 19th June, 29th June and 9th July. The response of earliest date of sowing, i.e., T1 (Control) and the corresponding date of disease confirmed (30th June) was found most effective, having least disease development (score 4.1) and highest grain yield (28.8 Q/ha), which was followed by the T2 having confirmed BLB (10th July) with slight  higher disease intensity (score 5.4) and less grain yield (26.8 Q/ha). The most harmful condition was observed in T4 with heavy intensity of disease (score 8.0) and least grain production (22.4 Q/ha). It was revealed from the experimental findings that delay in sowing and the development of BLB disease and considerable reduction in yield. The intensity of the disease increased gradually in field as the plant grows older. Maximum disease development was favored on matured crop plants having the range of temperature 30.1°C to 33.1°C, relative humidity 79.1-91.2 % without rainfall. Disease intensity was observed in almost linear relation with the increase in temperature in both the years of experimentation.