ARBORICULTURE & CONTENTS URBAN FORESTRY Volume 47, No. 1, January 2021 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) Cecil Konijnendijk Editor’s Note: A Call to Action ......................................................................................................1 F.D. Cowett, N.L. Bassuk, J. Grace, and K. Vorstadt Tracking Changes to Urban Trees over 100 Years in Ithaca, NY, USA ......................................3 Abstract. Municipally managed urban trees provide environmental, social, and economic benefits. Continued provision of these benefits depends on the health and sustainability of these trees, which depends in turn on tree managers having the type of information usually found in a tree inventory. The city of Ithaca, New York, USA possesses 7 inventories of its street and park trees dating back to 1902. This paper uses the data contained in these inventories to assess the health and sustainability of the city’s street and park tree populations. Attention is given to the structure of these populations with emphasis placed on species and genera diversity and DBH size class distributions. Prior to 1987, the city’s municipal tree population was dominated by a few species, such as Norway maple (Acer platanoides), and genera such as maples (Acer) and elms (Ulmus), and the DBH size class distribution was skewed unsustainably towards older trees. From 1987 onwards, new plantings have sig- nificantly increased species and genera diversity, and the DBH size class distribution suggests sufficient younger trees to account for tree mor- tality and removals. These changes did not occur quickly due to the persistent legacy effect of past planting preferences and practices, but required a consistent effort by municipal tree managers over many years. As a result, based on an analysis of the most recent tree inventory conducted in 2019, the city’s street and park trees and the benefits they provide look to be on a more sustainable footing, although challenges still remain. Keywords. Legacy Effect; Norway Maple; Species Diversity; Tree Inventory; Urban Tree Management. Joseph J. Doccola Activity of Stem-Injected and Soil Applied Imidacloprid Against Hemlock Woolly Adelgid in the Great Smoky Mountains .....................................................................................25 Abstract. Eastern hemlock (Tsuga canadensis [L.] Carrière) is an important component of the riparian ecosystem. Due to the widespread estab- lishment of hemlock woolly adelgid (Adelges tsugae Annand)(HWA) across the range of eastern hemlock, woodland trees may be infested for extended periods (years), resulting in their decline. Imidacloprid, a systemic neonicotinoid insecticide, may be used as a strategy in forested settings to manage HWA while more long-term solutions become established, such as biological controls. Symptoms of prolonged infestation include extensive dieback and thinned canopies. In this study, trees with a diameter at breast height (DBH) of 24.7 ± 2.7 SD cm in poor condition were treated with imidacloprid. Trees were treated once by trunk-injection (IMA-jet) or by soil drench in the Greenbrier area of the Great Smoky Mountains National Park, Gatlinburg, TN, USA. Changes in tree growth and HWA density were measured for 3 consecutive years. Imidacloprid- treated trees recovered, whereas the untreated trees declined. Imidacloprid treatments resulted in significantly higher 3-year mean percent growth (65.6% to 71.7% of tips) compared to the untreated controls (10.5% of tips). HWA density 3-year means in the imidacloprid-treated trees (0.10 to 1.09 per cm) likewise were statistically different to the untreated trees (2.72 per cm). The extended activity of imidacloprid-treated hemlock was attributed to storage in the symplast (xylem ray parenchyma) and to perennial needle retention. This study demonstrates that trunk-injection with IMA-jet is effective against HWA and comparable with soil drench to protect trees in the long term (≥ 4 years). Keywords. Hemlock Woolly Adelgid; Imidacloprid; Residual Activity; Soil Drench; Tree Injection. ©2021 International Society of Arboriculture
January 2021
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