an invasive urban forest pest invades natural environments ... an invasive urban forest pest invades
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An invasive urban forest pest invades naturalenvironments Asian longhorned beetle innortheastern US hardwood forests
Kevin J. Dodds and David A. Orwig
Abstract: An infestation of Asian longhorned beetle (ALB) (Anoplophora glabripennis (Motschulsky)) was detected inWorcester, Massachusetts, in 2008. The discovery of this pest, previously only seen in urban environments of North Amer-ica, led to the unprecedented establishment of a 243 km2 quarantine zone that included urban parks, neighborhoods, and nat-ural forests. Because ALB behavior in forested stands is virtually unknown, two closed-canopied forested stands (Bovenziand Delaval) infested with ALB within this zone were sampled during 20082010 to document stand conditions, assessALB host selection, and determine ALB impact on tree growth. Thirty-two percent of the Acer sampled in Bovenzi were in-fested with ALB compared with 63% in Delaval. In Delaval where three maple host species were available, ALB was foundmore often in Acer rubrum L. than in Acer saccharum Marsh. or Acer platanoides L. Radial growth patterns did not differbetween ALB-infested and uninfested Acer trees in Bovenzi. In contrast, ALB-infested trees in Delaval were significantlyolder and larger than uninfested trees and exhibited slower radial growth and ring width index patterns compared with unin-fested trees. Results suggest that if left uncontrolled, ALB can readily disperse into natural forest landscapes and alter themakeup of North Americas hardwood forest region.
Rsum : Une infestation du capricorne asiatique (CA) (Anoplophora glabripennis (Motschulsky)) a t dtecte en 2008 Worcester, au Massachusetts. La dcouverte de ce ravageur, observ jusqu maintenant seulement en milieu urbain en Am-rique du Nord, a entran ltablissement dune zone de quarantaine sans prcdent de 243 km2 qui incluait des parcs ur-bains, des quartiers et des forts naturelles. Parce que le comportement du CA dans les peuplements forestiers estpratiquement inconnu, deux peuplements forestiers avec un couvert ferm (Bovenzi et Delaval), situs lintrieur de lazone de quarantaine et infests par le CA, ont t chantillonns au cours de 2008 2010 pour documenter ltat du peuple-ment, valuer le choix dhte du CA et dterminer son impact sur la croissance des arbres. Trente-deux pour cent des ra-bles (Acer) chantillonns dans la fort de Bovenzi taient infests par le CA comparativement 63 % dans la fort deDelaval. Dans la fort de Delaval o trois espces drable taient disponibles, le CA a t retrouv plus souvent sur Acerrubrum L. que sur Acer saccharum Marsh. ou Acer platanoides L. Les patrons de croissance radiale des rables non infestset ceux des rables infests par le CA ntaient pas diffrents dans la fort de Bovenzi. Dans la fort de Delaval par contre,les arbres infests par le CA taient significativement plus vieux et plus gros que les arbres non infests et avaient des pa-trons de croissance radiale et dindice de largeur des cernes annuels plus lents comparativement aux arbres non infests. Lesrsultats indiquent que si aucune mesure nest prise, le CA peut facilement se propager dans les paysages de fort naturelleet modifier la composition de la fort feuillue en Amrique du Nord.
[Traduit par la Rdaction]
Forests of the northeastern United States have undergone aseries of invasions by organisms that have changed the com-position and structure of impacted stands (Orwig and Foster1998; Bohlen et al. 2004; Orwig et al. 2008). The first signif-icant introduction was in the late 1860s when gypsy moth(Lymantria dispar (L.)) was accidently released into Massa-chusetts forests. Subsequently, this species spread throughoutmuch of the eastern United States where at times it hascaused mortality to Quercus spp. and other tree species (Da-vidson et al. 1999). Two pathogens that arrived during the
20th century had a more species-specific impact than gypsymoth but nonetheless changed the structure and function ofnortheastern forests. The fungi associated with Dutch elmdisease (Ophiostoma novo-ulmi (Brasier) and Ophiostomaulmi (Buisman) Melin & Nannf.) and with chestnut blight(Cryphonectria parasitica (Murrill) M.E. Barr) altered thecomposition of forests and functionally removed Ulmusamericana L. and Castanea dentata (Marsh.) Borkh., respec-tively, from forest communities. In addition, the loss of Ul-mus spp. was dramatic in many cities and towns where theyhad been extensively planted and were a dominant fixturealong main streets (Campanella 2003).
Received 1 April 2011. Accepted 21 June 2011. Published at www.nrcresearchpress.com/cjfr on 29 August 2011.
K.J. Dodds. USDA Forest Service, Northeastern Area State and Private Forestry, 271 Mast Road, Durham, NH 03824, USA.D.A. Orwig. Harvard University, Harvard Forest, Petersham, MA 01366, USA.
Corresponding author: Kevin J. Dodds (e-mail: firstname.lastname@example.org).
Can. J. For. Res. 41: 17291742 (2011) doi:10.1139/X11-097 Published by NRC Research Press
. J. F
Invasive forest pests have wide-ranging impacts on forestedecosystems. Obvious impacts include effects on tree growthor increased tree mortality, resulting in changes in foreststand composition, structure, and nutrient cycling (Orwigand Foster 1998; DiGregorio et al. 1999; Orwig et al. 2008;Dodds et al. 2010). Nontree impacts, including effects onwildlife populations and (or) watersheds, can also occur(Tingley et al. 2002; Gandhi and Herms 2010). However, theimpact that invasive species are having on native commun-ities is often difficult to estimate accurately (Parker et al.1999). Factors such as tree resistance, time since establish-ment, ecosystem resiliency, and competition with native spe-cies must all be considered. Unfortunately, large informationgaps often exist when assessing impacts of invasive species.In cases where tree death is imminent and damage is ob-vious, estimating impacts and drawing conclusions based oninsect activity is generally straightforward. However, in caseswhere impacts are less obvious or tree mortality is not rapid,it is difficult to assess the true level of threat that an insectposes to an ecosystem type.The health of northeastern forests is currently threatened
by several species (e.g., beech bark disease, hemlock woollyadelgid (Adelges tsugae Annand), emerald ash borer (Agrilusplanipennis Fairmaire), European winter moth (Operophterabrumata L.), and Asian longhorned beetle (ALB) (Anoplo-phora glabripennis (Motschulsky)). ALB, considered one ofthe worlds 100 worst invasive species (Simberloff and Re-jmnek 2011), is of great concern to the region because ofthe ecological and economic importance of Acer spp., one ofits primary host genera. Acer spp. are commonly plantedalong streets, are a prominent component of the northernhardwood forests that range from southeastern Canada tocentral New England west to the Great Lakes region, and areeconomically important in the region for their colorful fall fo-liage and maple syrup products.ALB is native to China and Korea (Lingafelter and Hoe-
beke 2002) and has successfully invaded many parts of theworld (Hu et al. 2009; Haack et al. 2010). ALB has beenfound in several Western Hemisphere countries includingAustria, France, Germany, and Italy (Hrard et al. 2006,2009). Based on climate, much of eastern North America isconsidered at risk to this species (Peterson and Scachetti-Per-eira 2004). Several infestations have been found in NorthAmerica since the mid-1990s, including New York, NewYork (1996), Chicago, Illinois (1998), Jersey City, New Jer-sey (2002), Toronto, Ontario (2003), Carteret, New Jersey(2004), Worcester, Massachusetts (2008) (Haack et al. 2010),and most recently Boston, Massachusetts (2010) (NorthAmerican Plant Protection Organization Phytosanitary AlertSystem 2010). To date, the Worcester infestation is the onlyoutbreak of ALB where they escaped from urban settings andinfested closed-canopied forests. In addition, the scale of theWorcester infestation is the largest in terms of infested treesfound (>18 800), trees searched (>860 000), trees removed(>20 000), and size of quarantine area (243 km2) in NorthAmerica (Jones 2011).ALB is a polyphagous sapwood borer found in many hard-
wood species of Acer, Aesculus, Salix, Platanus, Ulmus, Be-tula, Populus, and occasionally other genera (Hu et al. 2009).Females locate host trees and chew oval oviposition pitsthrough the bark and into the phloem tissue where they lay
an egg. The egg hatches and the larva feeds in the phloemcambium area. After feeding in the phloem, ALB larvae be-gin mining into the sapwood where pupation occurs. Adultsemerge at least a year later but may take longer to complete de-velopment (Turgeon et al. 2007). ALB larval development canstructurally compromise trees and reduce the movement of pho-tosynthates, leading to physiologically weakened trees as well.Most North American infestations have been urban-fo-
cused and isolated from natural forests. In contrast, the ALBintroductions into Massachusetts are adjacent to large tractsof forests containing several species of Acer and other hostspecies. The proximity of this infestation to these forests pro-vides a pathway to even larger areas of northern hardwoodsdominated by Acer saccharum Marsh. and other economi-cally important tree species. An unprecedented effort isunderway to eradicate ALB from Worcester, and it is un-known at this time if these efforts will be successful. Becausemuch of the data collected on ALB behavior and damagecome from urban s