The Effects of Lawn Plant Diversity on Arthropod Diversity

The impact of lawn plant diversity on arthropod diversity was assessed in 40 residential lawns in Raleigh, NC.  This experiment used a factorial design to examine the effects of both lawn plant diversity and vegetative diversity surrounding the yard (vegetative complexity).  Arthropods were collected using pitfall and vacuum sampling methods, respectively, identified to the family level, and then assigned to functional groups (pests, beneficials, nonpest herbivores).  Diversity, evenness and abundance of functional groups and selected insect families were compared across treatments.  Abundances of ground-dwelling granivorous beetles and spiders were not influenced by lawn plant diversity or vegetative yard complexity; however, spider egg parasitoid abundance was greater in diverse lawns with simple yards and cricket abundance was greater in diverse lawns with complex yards.  Diverse lawns with complex yards hosted more diverse communities of foliar beneficial insects and the highest diversity and abundance of pest and nonpest insect species.  Abundances of selected beneficial families of parasitoid wasps (ichneumonids, mymarids, and scelionids) and selected pest families (membracids and phytophagous mirids) were higher in diverse lawns with complex yards.  Increased plant species diversity in lawns influences arthropod species diversity and abundance, however, only when vegetative yard complexity surrounding the lawn is high. Findings of this study suggest that low-maintenance, organic, or conventional lawn management strategies will not inherently require more pest management and that lawn pest management may depend on the vegetative complexity of the yard.