This thesis, presented in four chapters, focused on quantifying hemlock woolly adelgid (Adelges tsugae Annand) (HWA) mortality due to cold winters and insecticide treatments, seasonal phenology, and the persistence of systemic insecticides in eastern hemlock (Tsuga canadensis (L.) Carr.), the primary host of HWA, as well as in tree of heaven (Ailanthus altissima (Mill.) Swingle), the primary host of the invasive spotted lanternfly (Lycorma delicatula White) (SLF). In chapter one, phenology and winter mortality of HWA was observed at sites in Holland and Norton Shores, MI over two winters. Cumulative growing degree days (base 10 °C) associated with HWA life stages were monitored and general risk periods for management activities were established. Winter mortality was observed at both sites in January 2018 and 2019 when temperatures dropped below -20 °C. Data from detection surveys were used to map HWA distribution between 2016 and 2022. In chapter two, mortality of HWA due to systemic imidacloprid or dinotefuran applications was monitored over two years. Dinotefuran treatments provided nearly complete HWA control five months after application. Most imidacloprid applications provided HWA control the following year. Canopy condition of treated and untreated control trees was monitored from 2018 through 2021. In chapter three, persistence of imidacloprid and dinotefuran was quantified in foliage and twig samples from trees treated in 2016/2017 or 2018/2019 using two residue analysis methods. Effects of season and application method on concentrations over time were quantified. Most imidacloprid treatments persisted through 2020 at levels effective for HWA control, while dinotefuran was barely detectable in hemlock tissue. In chapter four, persistence and distribution of dinotefuran in foliage and phloem of tree of heaven were quantified in trees treated in 2019 at two sites. Dinotefuran was not detected in branch phloem and concentrations were inconsistent in trunk phloem.
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