Do anti-herbivory tubes impede bee visitations to flowering plants? Investigating possible unintended consequences of a common restoration practice

Introduction: Flowering plants are commonly used in restoration projects but can be difficult to establish because of herbivory. Mesh anti-herbivory tubes are often placed around plants to restrict access by herbivores, but no studies have investigated whether these tubes interfere with plant visitation by pollinators. Bees, in particular, rely heavily on visual signals to locate food sources and thus may be negatively affected by objects covering flowers. Objectives: The objective of this study was to investigate the effects of mesh anti-herbivory tubes (AHTs) on flower visitation by bees by examining potential effects of physical exclusion and visual deterrence. Methods: We compared five AHT treatments to a no-AHT control. We recorded visitation rates of bees to flowers relative to the presence and color of AHTs surrounding two native plant species, Munro's globemallow (Sphaeralcea munroana) and Showy fleabane (Erigeron speciosus). We also examined the reflectance spectra of the five AHTs and related this information to the color spectrum detected by bees. Results: Bee visitation to flowers was comparable across all treatments except for metal hardware cloth, which reduced bee visitation slightly relative to plastic mesh. Conclusions: We found that plastic mesh AHTs did not act as a physical or visual barrier for bees. Spectral analysis suggested that blue-painted and yellow-painted mesh may be more visible to bees than unpainted or clear-painted mesh, which is typically used in restoration plantings.