We conducted over a decade of research into individual eastern hemlock (Tsuga canadensis; hemlock) trees that are potentially resistant to hemlock woolly adelgid (Adelges tsugae; HWA), an invasive xylem-feeding insect that is capable of rapidly killing even mature trees. Following clonal propagation of these individuals, in 2015 we planted size- and age-matched HWA-resistant and HWA-susceptible hemlocks in HWA-infested forest plots in seven states. In 2019, we re-surveyed the plots; 96% of HWA-resistant hemlocks survived compared to 48% of susceptible trees. The surviving HWA-resistant trees were also taller, produced more lateral growth, retained more foliage, and supported lower densities of the elongate hemlock scale Fiorinia externa, another invasive hemlock pest, than the surviving HWA-susceptible trees. Our results suggest that HWA management may benefit from additional research exploring the identification, characterization, and use of HWA-resistant eastern hemlocks in future reforestation efforts.
Introduced willows have mostly been employed as a renewable feedstock for bioenergy in the northeastern USA. The question of whether introduced willows provide the same biodiversity value and attractiveness as native willows has not yet been explored. The objective of this study was to compare the attractiveness of native and introduced willows to different subfamilies of bees. The common garden experiment planted at Storrs, CT, USA, included three native (S. eriocephala, S. sericea, S. lucida) and three introduced (S. ‘SX64’, S. ‘Onondaga’, S. ‘S365’) willows. Various willow taxa flowered at different times through spring, allowing pollinators to be collected over a 6-week period using colored bowl traps. As a result, 2430 bees were collected and identified to the subfamily level. Andreninae was the most prevalent pollinator visiting all taxa of willows, followed by Hylaeinae and Colletinae. There were no significant differences in the number of pollinators collected from either native or introduced taxa during the progressive willow flowering during mid-March–May of 2021 and 2022, suggesting their equal attractiveness to pollinators. Similarly, during the concurrent flowering of the two native and two introduced taxa, there were no significant differences in the number of pollinators associated with either group suggesting that when pollinators had foraging choices, they were similarly attracted to both native and introduced willows. The overall finding of this study suggested that plantings of either native or introduced willows to meet bioenergy goals offer similar benefits of floral resources for pollinators.
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