Airborne Dispersal of San Jose Scale, Quadraspidiotus perniciosus (Comstock) (Homoptera: Diaspididae), Crawlers Infesting Apple

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

PHENOLOGY OF THE SAN JOSE SCALE (HOMOPTERA: DIASPIDIDAE) IN NEW YORK STATE APPLE ORCHARDS

Pheromone trapping studies from 1979 to 1981 showed that there were two periods of San Jose scale, Quadraspidiotus perniciosus (Comstock), male flight activity annually in western New York apple orchards. Spring flight, which resulted from overwintering black caps, began at ca. 94-140 degree-days (base 10 °C from 1 March) and occurred during bloom in the apple varieties studied. First generation crawlers emerged at ca. 360 degree-days. Second generation crawlers emerged at ca. 890 degree-days and were active throughout September. Regression analyses showed a logistic relationship between crawler density and fruit infestation, and inverse linear relationships between pheromone trap catches and San Jose scale infestation levels within tree