On insecticide-free pear trees in an orchard in central Pennsylvania, there was a low correlation between milligram fructose equivalents of foliar honeydew and numbers of pear psylla,Psylla pyricolaFoerster, nymphs per leaf, with the exception of 2 weeks in mid-July when little rainfall occurred (0.13 cm/week). The percentage of sooty-mold-damaged pears was significantly correlated with the seasonal average of nymphs per leaf but not with the seasonal average of foliar honeydew levels. In addition, the seasonal history of pear psylla was monitored on the same trees and early-season pear psylla development was related to pear tree phenology. There were three generations of pear psylla, the second being the largest and most important in regard to fruit development and damage.