Population Dynamics of Rice Blue Beetle, Leptispa pygmaea Baly (Coleoptera: Chrysomelidae)

Field experiments to study the influence of weather factors on the population dynamics of rice blue beetle, Leptispa pygamea Baly were undertaken at the Regional Agricultural Research Station, Pattambi, Kerala Agricultural University during first and second crop seasons, 2005. The field population of L. pygmaea was highest during 28^th standard week ending in 15^th July in the first crop season and during 40^th standard week ending in 7^th October in second crop season. The peak population in the field was found to be coinciding with the early tillering stage and thereafter showed a declining trend. The maximum temperature ranged from 29.8^oC to 31.8^oC and the minimum temperature from 23.2^oC to 23.7^oC with 95% relative humidity during the peak periods in first and second crop seasons. The population revealed a negative correlation with maximum temperature and sunshine whereas a positive correlation was observed with minimum temperature and relative humidity. Rainfall showed no significant effect. A minimum temperature of 25.0^oC and relative humidity of 95% were found to influence peak population.