Woody plant biodiversity explains arthropod management interventions in residential landscapes

Residential landscapes are infrequently designed with principles of sustainability in mind, which often results in the extensive use of pesticides to suppress a diverse array of plant pests. In this study, we ask whether ecological theory can inform the sustainable design and management of woody plant communities on urban residential properties. The associational resistance hypothesis posits that increasing biodiversity can inhibit the abundance of herbivores. Importantly, theory suggests that it might not just be diversity that matters, but the right kind of diversity (i.e., community composition). Previous studies have demonstrated that herbivore abundance can be greater on native plants compared to exotic plants in residential landscapes. However, little is known regarding whether this translates into greater numbers of interventions to reduce damage associated with plant pests on native plants. To test these hypotheses, we utilized a multi-year, commercial plant health care program dataset. We examined at the residential property scale the relationships between woody plant biodiversity and the percentage of plants that were native and pest management interventions, a metric of direct relevance to residents and plant health care practitioners. We found that the number of pest management interventions targeting phytophagous arthropods was negatively related to woody plant biodiversity. The percentage of native plants on a property had no relationship with the number of pest management interventions that occurred. Consequently, efforts to increase woody plant biodiversity in residential landscapes could result in increased phytophagous arthropod pest suppression, thereby diminishing the need for pesticide applications and their associated adverse effects.