126 signs of decline (Haack et al. 2002; Cappaert et al. 2005; Poland and McCullough 2006). Oſten, EAB is detected in an area only aſter trees have begun showing symptoms of invasion (e.g., crown dieback and epicormic shoots) and, by this time, the popula- tion has usually expanded to the level where local eradication efforts via tree removal and treatment is prohibitively expensive and labor intensive (Cap- paert et al. 2005; Poland and McCullough 2006). The success of management programs to maintain the health and utility of urban ash resources depends on the early detection of EAB and a rapid response (McCullough and Mercader 2012). Such a response to EAB invasions may be hampered, however, by limitations in current detection methods for EAB, including purple prism traps, girdled trap trees to attract and capture flying adults, and visual surveys. Purple prism traps baited with ash volatiles are com- monly used in monitoring programs (Crook et al. 2008; de Groot et al. 2008), and are sensitive enough to allow for detection of EAB as early as one year aſter its introduction to a new area (Knight et al. 2013). Girdled trap trees are also effective monitoring tools because stressed trees are generally more attractive to EAB (McCullough et al. 2009a; McCullough et al. 2009b). However, these methods provide little infor- mation about which trees have been attacked or the rate at which ash trees are likely to decline in the community. Visual surveys, on the other hand, have the potential to provide critical information regard- ing which trees are attacked, but signs and symp- toms of EAB infestation oſten do not appear until trees are heavily infested (Cappaert et al. 2005). Urban foresters routinely conduct street tree inventories to develop plans to improve forest health and manage hazards resulting from failing trees. During these inventories, each tree is oſten assigned a health ranking that indicates the overall condition of the tree. However, it is unclear how this assessment of tree health relates to the likelihood of EAB infestation. Objectives of the current study were to 1) determine borer-associated characteris- tics of tree decline that predispose native ash trees to attack by EAB, and 2) relate these characteris- tics to rates of ash decline in urban forests infested with EAB to develop an assessment-based detection method. Such a tool will leverage current street tree inventories, by enabling affordable and sensitive early detection of EAB, and empower urban forest- ©2015 International Society of Arboriculture Hughes et al.: Borer-Specific Assessment Scheme ers to catalyze community support for early inter- vention of EAB populations to save their ash trees. MATERIALS AND METHODS Borer-Specific Assessment Scheme A borer-specific assessment scheme was developed to enable urban foresters to identify trees most likely to come under attack by borers. The assess- ment scheme was based on two individual ranking schemes of tree vigor: 1) the International Society of Arboriculture scheme (ISA 2013), and 2) The Davey Tree Expert Company scheme (Zelaya, pers. comm.). The first scheme was chosen because it is most widely used by consulting arborists. The other scheme was chosen because of its capacity to rate the occurrence of specific symptoms of tree stress to better predict the presence of borers. Initial tree rankings consisted of Good, Fair, or Poor, follow- ing the vigor classes outlined by the ISA scheme. Trees rated “Excellent,” “Very good,” “Critical,” and “Dead” were excluded from the analysis because trees of these conditions are typically rare in urban landscapes. Trees in the “Critical” and “Dead” cat- egories pose an unacceptable risk in most urban landscapes, and are oſten removed by arborists, while the stresses of urban environments oſten pre- clude trees in the “Excellent” and “Very good” cat- egories. In fact, a recent survey of ash in the City of Indianapolis indicated that trees in these categories represented <2% of the total ash trees (Peper et al. 2008). Each tree was rated according to those as- pects of tree ranking schemes that are most likely to indicate the presence of borers, including crown thinning, biotic factors, and structural problems (Table 1). Vigor class was assigned according to the lowest ranking in any category. For example, a tree with no sign of borers, a full crown, but minor struc- tural damage would be rated “Fair.” Woodpecker markings and epicormic shoots were rated as absent (Good), present (Fair), or abundant (Poor/Critical). Experimental Design The study began in 2010 at two sites: Lafayette, In- diana (Tippecanoe County) where EAB was absent, and Indianapolis, Indiana (Marion County) where EAB was first detected in 2006, and the popula- tion was established and growing. In June, aſter
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