Invertebrate diversity in peri-urban community gardens and possible mechanisms of community assemblage

Abstract

Abstract Urban farming is becoming increasingly popular to address food insecurity in the U.S., especially in response to the COVID-19 pandemic. However, a major challenge on urban farms is pest identification and management. In addition, urban farms are diverse and occur in nonmetro and metropolitan areas alike, therefore tailored recommendations for pest management are needed to reflect this diversity. The primary objective of this study was to describe invertebrate community composition at 10 urban community gardens across two counties in Indiana. We also aimed to identify possible mechanisms that determine community assemblages, such as garden size, surrounding land use, ground cover management, and crop diversity. Using pitfall traps, sticky cards, and visual assessments, we determined that herbivores represent the dominant feeding guild at community gardens, and herbivore counts were highest on zucchini and tomato. However, sentinel prey releases determined that predators and parasitoids are important regulators of pest populations. Overall, the assemblage of feeding guilds was similar across sites, suggesting a common metapopulation present in the surrounding landscape. On-farm practices that had the greatest influence on insect diversity were crop diversity, the presence of floral resources, and ground cover management. Insect diversity was positively correlated with crop diversity, and pollination activity was associated with flowering crops, namely dill. Parasitoid counts on sticky cards were often associated with sites that had additional ground cover. This study provides useful insights on the dominant invertebrate groups present at urban community gardens in Indiana and accessible on-farm practices to improve farm biodiversity.