The aerial dispersal of San Jose scale, Quadraspidiotus perniciosus (Comstock), crawlers within the apple tree canopy and between trees was positively correlated with the seasonal abundance of crawlers on the bark. Airborne crawlers were significantly more abundant within the upper portions of the canopy and in the northeast and southeast quadrants. These data supported observations on variations in crawler density by location on the host and suggested that wind direction may have affected the distribution of crawlers dispersing aerially within the trees. The magnitude of aerial dispersal between trees was related to the levels of airborne dispersal within the canopy and the distance to the infested sourc
