Influence of Plant Community Structure on Natural Enemies of Pine Needle Scale (Homoptera: Diaspididae) in Urban Landscapes

Pine needle scale, Chionaspis pinifoliae (Fitch), is a pest of many species of conifers in urban habitats and Christmas tree farms. We found that the scale was abundant in impoverished habitats, such as ornamental landscapes, and scarce in more natural, park-like habitats. Rates of parasitism were highest in impoverished habitats, suggesting that parasitoids were not effective in suppressing scale populations. Generalist predators, however, were more diverse and abundant in natural habitats and appear to be more effective in controlling scales in structurally complex plant communities. Total densities of arthropods and densities of plant-feeding species were greatest in impoverished habitats, suggesting that populations were poorly regulated. Outbreaks of pine needle scale in ornamental landscapes and Christmas tree farms may be discouraged by increasing plant structural and species diversity to favor natural enemies.