The economic threshold level is a key factor to be studied for control of pear psyllid, Cacopsylla pyricola (Foerster) which has been recorded as a key pest on pear trees in North Sinai and Ismailiya Governorates, Egypt (Ahmed, 2007). This pest caused considerable losses in pear fruit yield in most of pear orchards.Ecological studies showed that the seasonal abundance of this species begin to be active from early March and continued to mid June under climatic conditions of Ismailiya Governorate. The present study aims to evaluate the economic threshold level of infestation on pear trees. Results of statistical analysis showed, when population density of C. pyricola was (13.7 nymphs / twig) it could be regarded as an economic threshold of infestation with C. pyricola on pear trees, at this level it is sufficient time for initiation of control measures.