Community Structure of Phytophagous Arthropods on Apple

The phytophagous arthropod community on apple was studied in Virginia, West Virginia, Pennsylvania, and New York in 1983 and 1984. Managed, “organic” (reduced management), and abandoned orchards were sampled and the arthropod communities therein were compared to examine the effects of orchard management on the community. Williams's index, species richness, and evenness all showed significantly greatest diversity in abandoned orchards, intermediate diversity in “organic” orchards, and least diversity in managed orchards. Diversity in the “organic” orchard decreased during the 2 yr of study, showing the cumulative effect of orchard management on the system. Similarity among orchards, within management class, ranged from 28 to 60%. Percentage of similarity and diversity indices indicated that cultivar and orchard age differences were not significant factors in comparisons among orchards. Communities were dominated by r-selected species in managed orchards and K-selected species in abandoned orchards. Community structure is hypothesized to be regulated by human-induced, environmental factors in managed orchards and by natural enemies in abandoned orchards.