Sap-feeding insects do not respond uniformly to urbanization: the role of urban green spaces and species characteristics

Urbanization leads to an increase in built-up areas but also creates landscape element mosaics, providing various habitats for phytophagous species. Sap-feeding insects (Hemiptera) form a major component of arboreal insect communities with many highly damaging and difficult-to-control pests of urban trees. Outbreaks of their populations are often reported from city centers. Here, we studied how urbanization (defined as the proportion of impervious surfaces within a 200 and 500-m radius) affected canopy-dwelling phytophagous hemipterans (true bugs, true hoppers, and psyllids) on field maple (Acer campestre) trees. We also considered the amount of green urban areas (gardens and parks) in the surrounding landscape and the characteristics of the hemipteran species (origin, diet, and body size). We found that sap-feeding hemipterans did not show consistent responses to urbanization. The occurrence of only one species (Alebra wahlbergi) increased while the abundance of other native species (e.g., Acericerus ribauti, Palomena prasina, and Rhinocola aceris) decreased with increasing level of urbanization. At the same time, the serious pest of urban trees, Metcalfa pruinosa, but also two major crop pests, Nezara viridula and Halyomorpha halys had the highest numbers at an intermediate level of urbanization with a relatively high proportion of gardens and parks in the landscape. We also found less native and more generalist hemipterans in highly urbanized sites compared to less densely built areas. Our results suggest that, apart from their substantial contribution to ecosystem services, green urban areas can favor some major insect pests of urban trees and agricultural crops.