ARBORICULTURE ARBORICULTU & CONTENTS identity and its relationship to URBAN FORESTRY Volume 44, Issue 3, May 2018 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) ® www.isa-arbor.com Camilo Ordóñez, Vadim Sabetski, Andrew A. Millward, James W.N. Steenberg, Amber Grant, and James Urban The Influence of Abiotic Factors on Street Tree Condition and Mortality in a Commercial- Retail Streetscape .....................................................................................................................133 Abstract. It is challenging to successfully grow trees in highly-urbanized areas, such as downtown commercial-retail districts. As part of a streetscape revitalization project, initiated in 2010, 133 London planetrees (Platanus × acerifolia) were planted in structural soil cells along the downtown, commercial district of Bloor Street in Toronto, Ontario, Canada. Aſter most trees experienced severe decline, with many dying, all trees were removed and replaced in 2015. This research reports on an investigation of multiple abiotic factors that may have con- tributed to the decline and mortality of the Bloor Street trees. Researchers collected cross-sectional data on soil texture, soil compac- tion, soil chemistry, built-environment characteristics (e.g., proximity to road intersections, pit or bed planter), sunlight availability, and historic data on tree condition and mortality, and analyzed them with multivariate statistical techniques (e.g., correlation, MANOVA, con- tingent, and ANOVA tests) to investigate the potential for relationships to tree mortality (mortality rate of 46.6% before removal) and tree condition. Results indicate that trees that were alive and demonstrated better structural and foliar condition before removal in 2015 had sig- nificantly lower levels of soil salinity and alkalinity, sunlight exposure, and signs of physical damage, suggesting co-occurring and cumula- tive impact of these variables on tree performance. Modification to streetscape design can ameliorate tree decline in the long term, while education targeted at raising awareness about de-icing salt application and irrigation practices will lessen tree stressors immediately. Key Words. De-Icing Salts; London Planetree; Platanus × acerifolia; Structural Soil Cell; Sunlight Availability; Toronto; Urban Soils. ® Rachael A. Sitz, Marcelo M. Zerillo, Jacob Snelling, Jorge Ibarra Caballero, Kathleen Alexander, Kendra Nash, Ned A. Tisserat, Whitney S. Cranshaw, and Jane E. Stewart Drippy Blight, a Disease of Red Oaks in Colorado, U.S., Produced from the Combined Effect of the Scale Insect Allokermes galliformis and the Bacterium Lonsdalea quercina subsp. quercina ....................................................................................................................................146 Abstract. Drippy blight is an emergent disease of red oaks, caused by the interaction between a kermes scale insect (Allokermes galliformis) and a bacterium (Lonsdalea quercina subsp. quercina). Multi-locus pathogen’s other phylogenetically related sequence analysis was used to confirm the bacterial Enterobacteriaceae species. Further, Koch’s postu- lates were performed on sapling red oaks. Prior to the discovery of drippy blight disease in Colorado, in the United States, the bac- terium was reported on oak trees in California but was limited to acorn infections. The scale insect, A. galliformis, was previously known to occur on pin oak in the eastern United States but was not previously associated with either this bacterium or the production of significant branch dieback associated with drippy blight. In addition to a description of this new disease, this research docu- ments a host range expansion of L. quercina subsp. quercina to northern red oak (Quercus rubra), Shumard oak (Q. shumardii), and pin oak (Q. palustris) and extends the reported host range of A. galliformis to include northern red and Shumard oaks. Key Words. Allokermes galliformis; Bacteria; Colorado; Drippy Blight; Lonsdalea quercina, Red Oak; Scale Insect. ©2018 | International Society of Arboriculture | ISSN:1935-5297
May 2018
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