Agricultural management and landscape drivers of arthropods associated with Cucurbita pepo in urban agroecosystems

Abstract

Agricultural habitat and landscape factors influence arthropod community structure in urban agroecosystems, thereby influencing the crucial role that arthropods play in supporting ecosystem services, such as biological pest control. Top-down regulation can be enhanced or diminished by shifts in arthropod communities, thus, understanding which factors alter abundance and richness of herbivores and natural enemies in agroecosystems can guide approaches to habitat management and pest control strategies. We examined which local habitat factors (e.g., ground cover, floral abundance, vegetation height) and landscape factors (e.g., urban cover) drive changes in herbivore and natural enemy abundance, richness, and composition on squash (Cucurbita pepo) plants in urban agroecosystems. We collected and identified arthropods from foliage, stems, and flowers using visual surveys on C. pepo plants across 21 urban agroecosystems in the central coast of California. Both local and landscape factors were associated with shifts in abundance and richness of specific herbivore and natural enemy taxa. Specifically, squash area was associated with higher abundance of leaf beetles and herbivore Hemiptera and herbaceous plant richness tended to predict lower herbivore, aphid and leaf beetle abundance. Squash area was associated with higher natural enemy abundance and richness, higher spider and ladybeetle richness, and higher predator Hemiptera abundance. Garden size boosted natural enemy and ladybeetle abundance and ladybeetle richness. Tree and shrub abundance was associated with higher spider, ladybeetle, and predator Hempitera abundance. Herbaceous plant richness was associated with lower ladybeetle abundance and richness. Finally, urban cover boosted predator Hemiptera abundance and richness. No local or landscape factors predicted shifts in herbivore or natural enemy composition. We examine why and how specific local and landscape habitat factors shape the arthropod community structure in a common garden crop and consider implications for garden management practices.