ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 38, Issue 3, May 2012 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) ® www.isa-arbor.com Daniel W. McKenney, John H. Pedlar, Denys Yemshanov, D. Barry Lyons, Kathy L. Campbell, and Kevin Lawrence Estimates of the Potential Cost of Emerald Ash Borer (Agrilus planipennis Fairmaire) in Canadian Municipalities ............................................................................................................. 81 Abstract. Emerald ash borer (EAB) is an invasive phloem-feeding insect causing extensive mortality to ash (Fraxinus sp.) in North America. Eco- nomic costs associated with EAB-related mortality of street and backyard trees in Canadian urban areas were estimated over a 30-year time horizon. The approach employed a simple spread model to approximate EAB arrival times at each community based on three maximum spread rates: slow (~10 km/year), medium (~30 km/year), and fast (~50 km/year). Costs are estimated for four discount rates (0%, 2%, 4%, and 10%) and three treat- ment rates (0%, 10%, and 50% of trees treated with an insecticide). Ash density along urban roads was estimated from a variety of sources, including a recently developed survey that allows for rapid assessment of street tree compositions. Based on the 30 km/year spread rate, a 4% discount rate, and a 10% treatment rate, the present value of the costs is estimated to be approximately CAD $524 million (2010 currency rate); this value increases to roughly $890 million when costs associated with backyard trees are included. These estimates are conservative because they focus only on damage to street (and backyard) trees; nonetheless, their magnitude suggests considerable justification for investments to slow the spread of EAB in Canada. Key Words. Agrilus planipennis; Canada; Cost-benefit Analysis; EAB Spread Model; Fraxinus; Urban Forest Management. ® Yolanda F. Wiersma, Troy L. Davis, Elizabeth C. Eberendu, Ian Gidge, Maria Jewison, Hiliary C. Martin, Kaylah C. Parsons, Heidi Patterson, and Ashley Quirke Hurricane Igor Impacts at Northern Latitudes: Factors Influencing Tree Fall in an Urban Setting ........................................................................................................................ 92 Abstract. Hurricane Igor was a Category 1 hurricane when it passed the island of Newfoundland, Canada, causing extensive damage. Hurri- canes are uncommon at northern latitudes, and boreal species are not adapted to hurricane-force winds. Moreover, much of the storm damage was in the urban area of the City of St. John’s, where there are also numerous non-native trees. This research tested whether there were attri- butes of trees (e.g., height, diameter at breast height, slenderness, species, age, or distance to nearest tree) that may have influenced whether a tree fell or was leſt standing. The study authors sampled 70 trees and found that DBH was a significant predictor of tree fall (snapping or uprooting). Conifers were no more or less likely to fall in the storm than deciduous trees, nor were native trees more or less susceptible to wind damage than non-natives. These results suggest that for a boreal, urban ecosystem, there are no target species available that could be planted strategically to minimize risk of tree fall in a major wind event. Thus, to minimize storm damage to human-built infrastruc- ture in regions where hurricanes are rare, the best strategy would be to avoid having large trees located in close proximity to infrastructure. Key Words. Abies balsamea; Acer platanoides; Acer pseudoplatanus; Betula papyrifera; Boreal Forest; Hurricane; Picea mariana; Tilia americana; Tree Damage; Urban Forest; Wind Damage. J. Veilleux, J. Leferink, and N.J. Holliday Rapid Removal of Symptomatic Trees Reduces Dutch Elm Disease Infection Rates ...................... 99 Abstract. In the province of Manitoba, Canada, 14 communities were paired on the basis of size and location. From 2004 to 2010 in one member of each pair, rapid removal of American elm (Ulmus americana) trees that displayed symptoms of Dutch elm disease was practiced: newly symptomatic trees were removed within six weeks of symptom detection. The remaining member of each pair continued with autumn or winter removal of symptomatic trees. Treed urban study areas were selected in each community, and in 2008 an inventory of U. americana was taken in these areas. From this inven- tory and from records of tree removals, estimates of the number of living U. americana and prevalence of Dutch elm disease were made for each year from 2004 to 2010. Following the switch to rapid removal, the annual prevalence of Dutch elm disease in rapid removal communities was 1.5 ± 0.2%, significantly lower than in communities with autumn/winter removal (3.1 ± 0.4%). The study authors estimate that in similar areas the value of the elm resource aſter 10 years would be almost CAD $600,000/km2 greater if rapid removal rather than autumn/winter removal were practiced. There- fore, under conditions similar to those in these communities, rapid removal should be a component of management programs for Dutch elm disease. Key Words. American elm; Hylurgopinus rufipes; Ophiostoma novo-ulmi; Sanitation; Tree Removal; Ulmus americana. ©2012 | International Society of Arboriculture | ISSN:1935-5297
May 2012
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