80 Sadof et al.: Restoration Capacity and Costs of Managing the Emerald Ash Borer in Urban Forests strategies that increase the number of treated trees will increase the size of the regenerated forest (Figure 2; Figure 5). Thus, the optimal strategy (Kovacs et al. 2010) of protecting only the largest trees (DBH > 61 cm) produces a forest that is smaller than when trees with a DBH as small as 30 cm are also protected (Figure 2). Strategies that rely on treating and removing ash trees without replacement generally produce a smaller regen- eration forest than those reliant upon replanting (Figure 2b). Nevertheless, among options that remove trees without re- placement, the size of the forest increases as the number and/ or size of the trees treated gets larger. Interestingly, the strat- egy of protecting the larger trees (DBH > 30 cm) and remov- ing the small trees kept the relative forest size relatively static with its lowest point (71%) at the completion of tree removal and its highest point at 106%, during the 25-year simulation. Initially the cumulative costs of strategies that mix insecti- cide use and tree replacement relative to the cost of replacing all trees have a tendency of being more expensive than treating all ash trees with insecticide (Figure 3). Strategies that rely on replacement of trees are more expensive than those strategies that simply remove ash trees. Among removal or replacement strategies, the highest costs are for those strategies that protect the largest trees because of the expense of repeatedly treating larger trees with insecticides. Strategies that involve replace- ment of median size trees and or smaller have cost trajectories that surpass the cost of replacing trees near the end of the 25- year projection. In contrast, the strategies of saving larger trees (DBH > 30 or 61 cm) exceed the cumulative cost of replacing trees by 30% or 58%. The optimal strategy (Replace DBH < 61) has the lower of these two costs because the size of the forest it protects with insecticide (Figure 2) is much smaller than the strategy that also protects smaller trees (Replace DBH < 30). The cumulative cost of any strategy relative to the cost of re- placing the initial ash forest will vary with local differences in ash forest size and the cost of insecticide treatments, money, and tree removal (Figure 4). Indianapolis provides a good example of how a municipality can influence tree removal and planting costs. Historically, annual planting and maintenance costs in In- dianapolis are reported to be $8 per tree, a value that is less than one-third of the average expenditures for 19 cities ($25/year) studied in U.S. Forest Service Municipal Forest Resource As- sessments (Peper et al. 2008). Very large cities are often capable of reducing costs of pesticides below the EAB default values due to the competitive bidding process. In Fort Wayne, IN, during 2010, the bids received for annual soil injection of trees with a high enough rate of imidacloprid to kill EAB on large trees ranged between $0.41 and $1.08 per centimeter DBH (C. Tinkel pers. comm.). These rates are between 17% and 44% of the an- nualized application cost per tree used in this simulation, where trees would be treated only once every three years. As such, the yearly cost per centimeter DBH ($0.81) is a reasonable approxi- mation of what a city could expect to pay to treat all ash trees with insecticides (Table 1). Further reductions in the cost of tree removal may also be achieved by developing a tree removal plan that removes ash trees before EAB has killed them. This is es- pecially important for large trees where limb breakage during tree removals increase the need to use specialized and more ex- pensive procedures that reduce hazards to people and property. In summary, the study authors conclude that although some ash trees can be protected from EAB with insecticides, the long- term expense of this strategy is likely to drive some communities to rely heavily on tree replacement in their EAB response plans. From gypsy moths to Asian longhorned beetles, the development of an effective response to exotic invasive pests has required ur- ban forestry professionals to work with their communities to set mutually agreed upon objectives (Antipin and Dilly 2004; Lens- ing et al. 2008; Nealis 2009). Local opposition to the removal of live trees and the cost of a management program can derail attempts to implement even the most well-meaning of restora- tion plans (Vining et al. 2000). The EAB Cost Calculator can be used to evaluate approaches a community can take to select- ing trees for treatment based on DBH, ranging from maximiz- ing treatment effectiveness (DBH < 30 cm) to optimizing costs and benefits (DBH > 61 cm). As such, the current research demonstrates how the cost calculator can be used as a tool to help urban foresters engage their communities in the decision- making process by helping them discuss the consequences of management plans in terms of budgets and rates of restoration. Acknowledgments. Thanks to W. Hoover, J. Ellis, H. Holt, and R. McK- enzie of Purdue University, and K.F. Kovacs of University of Nevada, Reno, W. Diedrichs, S. Dickerson, P. Louks, B. Shaw, and C. Tinkel, of the Indiana EAB Task Force and J. Smith of Bayer Chemical for advice and technical support. Thanks to P.J. Peper, Center for Urban Forest Re- search USDA FS Pacific Southwest Research Station for providing data on ash tree size and age. This project was funded by a grant to CSS from the USDA APHIS PPQ and the Indiana Dept. of Natural Resources. ©2011 International Society of Arboriculture
March 2011
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
