Distribution and abundance of Lepidiota Albistigma in relation to soil physicochemical properties in lower brahmaputra valley of Assam

Population of Lepidiota albistigma grubs were estimated in five selected ecosystems of lower Brahmaputra valley of Assam during 2015–17. The study revealed that significantly more grubs were collected from grassland near water sources (8.52 ± 0.97, 7.56 ± 0.59 and 8.72 ± 0.91), followed by open grassland (4.96 ± 0.75, 5.06 ± 0.82 and 4.60 ± 0.89) and cultivated field near water sources (2.74 ± 0.83, 2.38 ± 0.92 and 2.54 ± 0.86) during 2015, 2016 and 2017, respectively. Existence of grubs in soil depth measured during April, 2015 to March, 2016 in grassland and cultivated fields revealed that maximum grubs confined up to 20 cm. Population estimation of growth stages from March, 2016 to February, 2017 revealed that adults appeared in March (0.4 A) with maximum during April 2016 (1.6 A). Grubs appeared from May (1.6 G), 2016 to January (0.6 G), 2017. Similar population of grubs (1.6 G) were recorded in May, July and September and peak population was observed in August 2016 (3G); pupae were observed in March (1.2 nos), April 2016 (0.8 nos), and February (1.4 nos) in 2017. Soil moisture studies revealed that it was maximum in April (27.63%) followed by July (24.38%) and October (24.32%). Correlation coefficients between grubs and sand (r =-0.693) and silt content (r =-0.845) were significant and negative, in contrast to the clay content (r = 0.839). Soil organic matter content (r = 0.901) and available nitrogen (r = 0.963) revealed significant positive correlations.