The objective of this study is to determine the Seasonal variation, percent infestation and effect of important weather factors viz. temperature (minimum, maximum, average), relative humidity (morning, afternoon and average) and average rainfall on population of woolly apple aphids, Eriosoma lanigerum Hausmann. Abundance of the pest was calculated on monthly basis in various apple orchards from March,2008 to February,2011, located in Jammu. Studies reveal that the pest remains active in the fields during March to December and suspends their activity during severe winters. It was recorded that there are two population peaks in a year, 1st in June and 2nd in August. Correlation analysis for aphid population densities indicate a highly significant positive correlation with minimum temperature, maximum temperature and average temperature (p