160 Sargent et al.: Emerald Ash Borer Within an Intensively Managed Quarantine Zone Arboriculture & Urban Forestry 2010. 36(4): 160–163 Dispersal of Emerald Ash Borer within an Intensively Managed Quarantine Zone Chris Sargent, Michael Raupp, Dick Bean, and Alan J. Sawyer Abstract. Emerald ash borer (EAB) (Agrilus planipennis) is one of the most destructive insect pests of urban trees in the United States. The objective of the current study was to determine the rate of spread of EAB in a quarantine zone where aggressive intervention tactics such as tree destruction occurred. Histori- cal records were examined from the Maryland Department of Agriculture for the years 2003, 2006, 2007, and 2008, to determine the rate of spread of EAB in Maryland, U.S., within the quarantine zone. Despite attempts at eradication and public education, EAB persisted, and the leading edge of beetles moved away from the central infestation point at an average annual rate of 1 km per year and a maximum annual rate of 1.37 km per year between 2003 and 2008. This paper discusses the relative merits and limitations of this quarantine and eradication program and makes suggestions for future management of EAB. Key Words. Agrilus planipennis; dispersal; emerald ash borer; eradication; quarantine; rate of spread. Emerald ash borer (EAB) (Agrilus planipennis), an invasive wood-boring beetle from Asia, was first detected in Michigan, U.S., in 2002. At the time of this writing, the serious pest has de- stroyed tens of millions of ash trees in thirteen states in the U.S. and two provinces in Canada. Emerald ash borer is a major threat to the sustainability of urban forests in North America (Cappaert et al. 2005; Raupp et al. 2006; Ghandi and Herms in press). Accu- rate knowledge of the rate of spread of EAB is imperative to help municipalities plan effective management strategies for this dev- astating pest (Smitley et al. 2008; Ghandi and Herms in press). Several approaches have been employed to estimate dispersal of EAB. One involved the use of tethered beetles in computer- monitored flight mills (Taylor et al. 2005; Taylor et al. 2007). Taylor et al. (2005) determined that mated female beetles flew farther than males, and the average distance flown by females in 24 hours was 1.7 km. A subsequent study confirmed the superior dispersal ability of females, but estimated a maximum flight dis- tance for EAB over several days to be 9.8 km (Taylor et al. 2007). Other approaches to estimating dispersal of EAB include direct observations of movement of the beetle from a point of release to a point of capture, or through reconstructing patterns of movement using historical records of beetle infestations and their damage. Haack and Petrice (2004) recorded dispersal of EAB from a central release point to trap logs placed at fixed dis- tances away from the point of release. Beetles were recovered at distances of 250 m and 1500 m, at two different release sites. McCullough et al. (2004) felled and examined trees surrounding a woodpile heavily infested with EAB. Approximately 70% of galleries were found in trees within 100 m of the woodpile, but one gallery was detected 750 m from the source. In a study that combined tree surveys and examination of felled ash trees, Smit- ley et al. (2008) determined that EAB infestation caused thinning of ash canopies. They sampled a large number of ashes radiat- ©2010 International Society of Arboriculture ing away from Canton, Michigan, the site at the epicenter of a regional EAB infestation. Smitley et al. (2008) determined the rate of spread of canopy thinning associated with EAB to be 10.6 km per year. Siegert et al. (2008) used dendrochronological re- construction and historical records to estimate the rate of spread of EAB in southern Michigan. They concluded that the spread of EAB from a historical epicenter was biphasic with a slow, early phase of about 6.5 km per year followed by the formation of satellite colonies about 20 km distant to the core infestation. Many of the before mentioned studies occurred in federal quar- antine zones, under a wide variety of management approaches ranging from minimal intervention, such as limiting the movement of wood and wood products, to more aggressive tactics, including insecticide applications and removal of infested and uninfested trees. The introduction of emerald ash borer to Maryland via an illegal shipment of infested nursery stock from Michigan pro- vided a unique opportunity to study dispersal of this pest within well-defined spatial and temporal dimensions in an area subjected to a federal quarantine and an aggressive eradication program. In April 2003, a nursery in southern Prince George’s County, MD, received a shipment of green ash (Fraxinus pennsylvanica) trees. A nursery inspector from the Maryland Department of Agricul- ture (MDA) noticed unusual exit holes on ashes in the nursery in August 2003, and the USDA Systematic Entomology Labora- tory in Beltsville subsequently confirmed the EAB infestation. Of the original 121 trees shipped from Michigan, 119 were re- covered either on site at the nursery, or at landscape sites through trace backs of sales. Ninety-six trees from Michigan still on site at the nursery were destroyed in September 2003, and 23 trees that were installed in landscapes were retrieved and destroyed. An ad- ditional 442 ash trees in the nursery from sources other than Michi- gan were removed and debarked to determine infestation. Seventy- one trees were found to be infested with a total of 303 larvae. The
July 2010
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