Hemlock woolly adelgid (Adelges tsugae Annand (Hemiptera: Adelgidae); HWA), a small insect originating from East Asia, was inadvertently introduced into the eastern United States in the 1950s. Since its introduction, the invasive insect rapidly spread through the range of eastern hemlock (Tsuga canadensis Carrière (Pinaceae)) and Carolina hemlock (T. caroliniana Engelmann (Pinaceae)), causing high tree mortality. In 2017 HWA was detected in Nova Scotia, Canada, where it is threatening local eastern hemlock stands and ecologically important habitats. Numerous management techniques, including silvicultural approaches, biocontrol, host-resistance research, and chemical control are currently being investigated to help manage the spread of HWA and mitigate damage to and loss of host trees. Treatment of infested trees with the neonicotinoid insecticide imidacloprid has shown high efficacy in the United States and Canada, stopping tree decline and preventing mortality. While effective against HWA, the use of imidacloprid has raised concerns regarding its potential impacts on non-target arthropods inhabiting hemlock forests. Many studies have explored the non-target effects of imidacloprid treatment for HWA management on arthropods, however, its effects on pollinators inhabiting eastern hemlock forests remain unclear. We conducted a two-year study (2021–2022) to explore the non-target impacts and risks associated with imidacloprid basal bark sprays for HWA management on two pollinator groups, bees (Hymenoptera: Apoidea: Anthophila) and flower flies (Diptera: Syrphidae) in eastern hemlock forests of Nova Scotia, Canada. Our objectives were to evaluate changes in the abundance, richness, and community composition of bees and flower flies before and after treatment and between treated and untreated (control) sites, and to assess imidacloprid concentrations in flowers within treated forest plots to determine potential risks to pollinators. Furthermore, we aimed to evaluate the efficacy of three collection methods, targeted sweep netting, colored pan traps, and blue vane traps, to provide tools for future monitoring of pollinators in this habitat. Although we did detect variation among the pollinator communities in the study, our findings indicated no clear evidence of adverse effects on pollinators from imidacloprid basal bark sprays. We did, however, detect imidacloprid in flowers at concentrations potentially harmful to pollinators, especially near treated trees, which underscores the need for further research into potential risks, especially if repeated and large-scale treatments are planned in the future. Additionally, we found that blue vane traps are particularly effective for sampling bees and flower flies in this habitat, though colored pan traps and targeted sweep netting may offer complimentary insights into the present pollinator community. Our findings on sampling method efficacy will equip researchers with the necessary tools to accurately monitor pollinator populations in eastern hemlock forests, aiding to evaluate effects of imidacloprid basal bark sprays on pollinators in the future.
Call Number
LE3 .A278 2024
Date Issued
2024
Supervisor
Degree Name
Master of Science
Degree Level
Masters
Degree Discipline
Affiliation
Abstract
Publisher
Acadia University