Phenology of fall dispersal into apple orchards is described for winterform pear psylla, Cacopsylla pyricola Foerster, in orchards located in Yakima and Wenatchee, Washington. Psylla in both regions first appeared on pear in mid to late September, reaching peak densities in late October or early to mid November, and then decreased in numbers to a low in December. Movement onto apple began in October; peak counts on apple occurred in late November to early December. There was considerable variation among years in phenology of leaf fall in pear and numbers of psylla entering apple. Leaf fall in pear was delayed in a cool, wet fall (1991) compared with warmer and drier years (1990 and 1992), and temperatures during leaf fall were consequently lower in 1991. Numbers of psylla moving onto apple were considerably lower in 1991 than 1990 or 1992. Catch on sticky traps and dispersal rates onto apple were both positively correlated with rates of leaf fall in pear, temperature, and density of psylla on pear.