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Spatiotemporal dynamics and host selection of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), at Point Pelee National Park, Ontario, Canada

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Title: Spatiotemporal dynamics and host selection of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), at Point Pelee National Park, Ontario, Canada
Author: Carson, Shelley-Lynne E.
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Otis, Gard W.
Abstract: The emerald ash borer (Agrilus planipennis; EAB) is a wood-boring beetle that was introduced to North America from Asia c. 1990. Larval feeding on ash trees (Fraxinus spp.) has caused extensive mortality of North American ashes. This study was initiated in the early stages of an EAB infestation at Point Pelee National Park in Essex County, Ontario, Canada to monitor an infestation in a natural environment, and included assessment of tree health and quantification of beetle emergence. A plot containing green and blue ash trees was established in 2008. Green ashes were heavily infested; blue ashes showed no signs of colonization. By 2011, all green ashes were dead while EAB had emerged from few blue ashes. Emergence had declined dramatically. Blue ash trees are not expected to suffer severe mortality at this site due to EAB infestation. Crown health and EAB emergence was assessed in 620 ash trees in six plots from 2008 to 2011. Exit holes left by beetles in 2006 and 2007 were also counted. Emergence was low in 2006, peaked in 2009, then decreased again despite the availability of suitable hosts. This is atypical of EAB infestations; the cause of this decrease is unknown. ‘Actively infested’ trees (new exit holes) were divided into ‘newly infested’ and ‘reinfested’. An increase in newly infested trees coincided with greater beetle emergence. The number of reinfested trees remained relatively constant. This suggests population increases result in local dispersal, and reinfestation reduces colonization of new trees. Finally, the influence of host and stand variables (tree diameter, crown position, surrounding basal area and stem count, and tree location) on EAB emergence was investigated. Using zero-inflated Poisson modelling, the influence of each variable on exit hole estimates and on the probability of no exit holes (suitable hosts not yet infested) was assessed. Separate models were generated for each year because ash tree mortality altered the surrounding habitat. Models indicated the infestation moved southward faster than eastward; host and stand variables slowed eastward movement. This suggested that female EABs selected hosts based on host and stand variables. The influence of these variables changed over time.
URI: http://hdl.handle.net/10214/7757
Date: 2013-10


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