Impact of Weather Parameters on Aphid Population in Cotton

A field experiment was conducted during 2004–05 and 2005–06 to study the effect of weather factors on aphid population in cotton. Aphid population was recorded for the first time in 28^th standard week, which remained active up to I^st standard week having its peak density (18.15/leaf) in 37^th standard week. Weather parameters namely maximum and minimum temperature and relative humidity showed positive correlation with aphid population and also increased at the rate of 1.3181, 0.5406 and 0.1939 per leaf with 1°C increase in minimum and maximum temperature and 1 percent increase in relative humidity, respectively. About 43.71 per cent variation in the population of aphid were influenced by the all weather parameters including rain fall. The direct contribution of minimum temperature was substantially positive and highest (0.510) followed by maximum temperature (0.281). Most of the weather parameters exerted their indirect contribution to the aphid population through minimum temperature.