The experimental fruit orchards located at Tenth of Ramadan Association of agricultural lands in Ismailia Governorate. This study was carried out to evaluate the effect of a biotic factor as age plant and abiotic factor maximum, minimum temperature and relative humidity from first march 2013 to end of November 2014. Correlation, regression analysis and multi regression between abiotic factors and population density of pear psylla was in liner degree but with age plant was polynomial degree. In addition, the combined effect of biotic factor (plant age) on the changes of Cacopsylla bidens eggs, nymphs and adult population represented by (88.87 , 87.45 and 85.02%) respectively, in 2013. While in the second year 2014 the value of E.V% was (82.44, 88.72 and 85.21%) for eggs, nymphs and adult, respectively. This revealed that the effect of plant age was a more effective factor on C. bidens abundance than weather factors. In this study one predator Orius albidipennis (Reut.) was recorded few numbers in spring and autumn season this predator fed on the egg stage of pear psylla.