Influence of Water Level in Rice Field on the Population Build Up of Nilaparvata lugens Stal and Incidence of Rice Brown Plant Hopper in Upland and Lowland Paddy

The average population of brown plant hopper and per cent damaged hills were significantly higher in immersing stem and leaf sheath level of water (3.83 nymph per hill, 2.26 adult per hill and 2.49 per cent damaged hills) as compared to normal level of water (1.72 nymph per hill, 1.45 adult per hill and 1.34 per cent damaged hills) and field capacity level of water (0.30 nymph per hill, 0.33 adult per hill and 0.54 per cent damaged hills). Which indicate higher level of water induce population of brown plant hopper. Regarding population development in paddy field, the per cent damaged hills (0.51), nymph population (0.56) and adult population (0.40) were significantly higher in lowland paddy as compared to upland paddy (0.32, 0.15 and 0.16, respectively).