Arboriculture & Urban Forestry 38(3): May 2012 Arboriculture & Urban Forestry 2012. 38(3): 81–91 81 Estimates of the Potential Cost of Emerald Ash Borer (Agrilus planipennis Fairmaire) in Canadian Municipalities Daniel W. McKenney, John H. Pedlar, Denys Yemshanov, D. Barry Lyons, Kathy L. Campbell, and Kevin Lawrence 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. Emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Bu- prestidae), is a metallic wood-boring beetle, native to Asia, that has destroyed millions of ash trees since being accidentally in- troduced to North America (Smith et al. 2009). During its larval stage, EAB feeds on the inner phloem and outer xylem of ash trees, leading to disrupted vascular flow and ultimately tree death (Cappaert et al. 2005). Once EAB becomes established in an area, about 30% of ash trees are killed each year (Herms et al. 2009a); very few host trees have shown any natural resistance, though blue ash (Fraxinus quadrangulata Michx.) and Asian ash spe- cies may be less susceptible (Anulewicz et al. 2007; Rebek et al. 2008). A number of insecticides have proven effective in protect- ing trees against EAB attack (Herms et al. 2009b; McKenzie et al. 2010); however, they are not likely to be widely applied because of considerations around cost, efficacy, and safety. Furthermore, EAB infestations are often difficult to detect until host trees show obvious signs of stress (McCullough et al. 2009), at which point it may be too late to reverse the damage (Herms et al. 2009b). Since being introduced into southern Michigan in the early 1990s (Cappaert et al. 2005), EAB has spread rapidly across east- ern and central North America, with outbreaks currently reported from 15 U.S. states and two Canadian provinces (USDA-APHIS 2011). Though a small percentage of mated females are capable of flying more than 20 km in 24 hours (Taylor et al. 2010), most larvae that originate from point source introductions are found within 100 m of adult emergence sites (Mercader et al. 2009). Thus, human-assisted dispersal via transport of infested ash material (Cappaert et al. 2005) and/or hitchhiking on vehicles (Buck and Marshall 2008) is likely the main cause of the ob- served EAB expansion (Prasad et al. 2010). Over time, EAB is expected to continue its advance across Canada and the United States, decimating ash in urban and rural settings along the way. Given its rapid rate of spread and the prevalence of ash in both natural and urban forests across much of eastern and cen- tral North America (Burns and Honkala 1990; Woodall et al. 2009), EAB clearly has the potential to bring about significant economic and ecological impacts. Several studies have produced regional economic impact estimates in the U.S. (Kovacs et al. 2010; Sydnor et al. 2007; Sydnor et al. 2011). The objective of the current study was to report on efforts to generate EAB- related cost estimates for Canadian urban areas. The approach employs a relatively simple spread model to coarsely simulate EAB expansion to Canadian communities over a 30-year period. For each community in the study area, costs related to ash removal, replacement, and treatment are estimated and then discounted according to the timelines projected by the spread model. The lack of spatial data on ash distribution and abun- dance in Canada presents a significant challenge for this type of study. A variety of sources were used to estimate ash abun- dance along urban streets, including early results from a sur- vey that allows rapid assessments of street tree composition. This research focused on street trees because they can be reli- ably and rapidly surveyed and are almost certain to require management action (i.e., removal/replacement or treatment) if attacked. This is an underestimation of total EAB impact. Regulatory efforts to prevent the introduction of alien species to Canada and associated research are federal responsibilities, while long term management of established pests requires strong ©2012 International Society of Arboriculture
May 2012
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