The susceptibility of an urban ash canopy to the emerald ash borer - a temporal and spatial analysis from Winnipeg, Manitoba, Canada

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Date
2022-08-16
Authors
MACDONALD, BRETT
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Abstract
The invasive emerald ash borer (Agrilus planipennis Fairmaire; Coleoptera: Buprestidae) was first detected in Winnipeg, Manitoba in 2017 and has the potential to become a serious threat to the city's extensive ash (Fraxinus spp.) canopy. The objectives of this thesis were to predict A. planipennis emergence and peak activity patterns in Winnipeg; and to determine the potential susceptibility of neighbourhoods to infestation. To predict adult emergence and peak activity of A. planipennis, we used local weather station data to calculate the number of degree-days accumulated in each year for the 1970–2019 period using three different degree-day accumulation models. The estimated mean emergence dates for the 50-year period were June 14 ± 8.5 days (double sine model), June 14 ± 8.5 days (single sine model), and June 19 ± 9.1 days (standard model). The peak activity dates were July 16 ± 8.8 days (double sine model), July 17 ± 8.7 days (single sine model), and July 21 ± 9.4 days (standard model). To determine the potential susceptibility of neighbourhoods, ash density (trees/ha) maps, Moran plots, and correlograms were developed to model how A. planipennis might spread throughout Winnipeg and the potential corridors that may facilitate beetle movement. This study found that private green ash trees along riverbanks may be of most concern to city managers as these trees have significant potential to influence how EAB disperses throughout Winnipeg. The management of private green ash (Fraxinus pensylvanica Marsh.) trees along riverbanks will be a major variable in how successful A. planipennis dispersal is throughout the city. The results from this study will provide managers with information regarding the predicted temporal and spatial behavior of A. planipennis in Winnipeg allowing for improved timing of control measures and monitoring.
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emerald ash borer, degree-days, management, conservation, invasive, spatial
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