DEVELOPMENT OF THE PHYTOPHAGOUS ARTHROPOD COMMUNITY ON APPLE AS AFFECTED BY ORCHARD MANAGEMENT

The phytophagous arthropod community in three apple orchards was sampled for the first 5 yr (1984-1988) after planting. One orchard was unmanaged, one was partially managed with pruning and weed control, and one was under full commercial management. For the first 2 yr there were no significant differences in arthropod diversity among the three orchards. In the third and subsequent years, diversity, as measured by species richness and Williams' index, was significantly lower in the commercially managed orchard than in the two reduced management orchards. In the fifth year, the commercially managed orchard had the most uneven distribution of species abundances and the partially managed orchard the most even. Within-year evenness values were more variable in the commercially managed orchard than in either of the reduced management orchards. Mean annual diversity in both reduced management orchards increased in the first 4 yr of community development and remained constant in the fifth year. In the commercially managed orchard, diversity increased in the second year, then declined and remained low. Within each year, diversity generally peaked in all orchards in middle to late summer. There were subtle differences between communities in the unmanaged and partially managed orchards. In the partially managed orchard, trees were larger and more vigorous than trees in the unmanaged orchard. The community in this orchard was dominated by species that were able to exploit the abundant succulent branch terminals, such as aphids (Homoptera: Aphididae) and Lyonetia speculella (Lepidoptera: Lyonetiidae).