BEE CONSERVATION IN URBAN LANDSCAPES: ASSESSING BEE ASSEMBLAGES, BEE–ATTRACTIVENESS, AND NUTRITRITIONAL VALUE OF WOODY LANDSCAPE PLANTS AND MITIGATING POTENTIAL BEE HAZARD FROM NEONICOTINOID INSECTICIDES

Public awareness of declining pollinator populations has increased interest in creating “bee–friendly” urban landscapes. I quantified bee visitation and assemblages of 72 species of flowering woody plants common in urban landscapes. I found strong plant species effects and variation in seasonal activity of particular bee taxa but no overall differences in bee visitation or genus diversity between native versus nonnative species or trees versus shrubs. Analysis of pollen from a subset of these plants revealed small but statistically significant differences in total and essential amino acids between native and nonnative species and trees and shrubs, although each group had species with high quality pollen. Uptake and dissipation of soil–applied imidacloprid and dinotefuran was measured in nectar and leaves of two woody plant species, Ilex × attenuata and Clethra alnifolia to assess concentrations to which pollinators might be exposed in landscape settings. Three application timings were evaluated. Residues in nectar and tissue were analyzed by HPLC–MS/MS in two successive years. Residues in nectar following autumn or spring applications exceed concentrations shown to adversely affect individual and colony–level traits of bees. Summer application mitigated concentrations of imidacloprid (8–31 ng/g), but not dinotefuran (235–1191 ng/g), in nectar