A PhD studentship is available to work as part of an international research group investigating the risks of establishment by the invasive Emerald Ash Borer beetle into the UK, northern Europe, and western Canada. By exploring the beetle’s relationship with temperature and host resistance, the project will determine how the cooler climates of these regions will influence the life cycle and rate of spread of EAB, model its potential impact upon different ash tree species, and ensure management strategies are the most appropriate for the climatic context.
Emerald Ash Borer, Agrilus planipennis (EAB) is a buprestid beetle native to China, Korea and Japan where it is a secondary pest of stressed and moribund ash trees (Fraxinus mandshurica and F. chinensis) and has no economic impact. Since its accidental introduction into North America however, it has had a devastating impact on all native ash species, including green, white and black ash (F. pennsylvanica, F. americana and F. nigra), which are highly susceptible to attack. Trees are killed within 3-5 years, and where the beetle is well established up to 99% of ash trees have been lost. Infestations have been reported from large areas of southern Ontario and Quebec in Canada, and in 30 US states, and the beetle is still spreading. Hundreds of millions of ash trees have been killed in the USA and Canada to date.
EAB has also been accidentally introduced to Russia, where it has spread outwards from Moscow on American green ash planted along roadsides. The threat to ash in Europe is now severe as EAB spreads south-west in Russia into areas where European ash, Fraxinus excelsior is a natural component of the landscape. From here the pest is expected to be able to spread unhindered toward central and western Europe. There is still considerable uncertainty however, over how susceptible F. excelsior is to attack. Field trials in the USA suggest that it is highly susceptible to EAB, but observations in Moscow indicate that not all F. excelsior are attacked and this species may possess a degree of resistance.
Another major uncertainty over the likely impact of EAB in Europe is how far and how rapidly the beetle will spread, particularly in the cooler maritime climate of the north and west. The current distribution of EAB in the USA, Canada and Moscow, encompasses areas with a continental climate and relatively high summer temperatures. It is not known whether EAB will perform equally well under a cooler and wetter climate such as that in the UK, and whether this might limit its rate of spread, abundance, and impact on ash trees.
Life-cycle duration and dispersal opportunities in insects are largely governed by temperature. For example, Asian longhorn beetle (Anoplophora glabripennis) has also been introduced into both North America and Europe, is similarly adapted to benefit from high summertime temperatures. Analysis of a recent outbreak in the UK showed that the beetle required 3 years to complete its life-cycle, compared to only 1 year in continental regions with higher summertime temperatures. Limited opportunities for dispersal also meant that the population remained small and contained, in a way not seen in warmer climates. The cooler summer temperatures experienced in the UK and in western Canada may similarly influence the life cycle and flight dispersal opportunities for EAB once it establishes there. The limited data available on the thermal requirements for EAB suggests an optimum development temperature of 25-30°C. In comparison, mean summer temperatures in forest habitats in the UK and western Canada are often around 15-20°C. Thus in combination with a potentially more resistant host tree in F. excelsior in Europe, it is possible that EAB populations may increase and spread more slowly than has been observed to date. This may provide opportunities to manage it in a way not achievable in its current outbreak area.
This project will determine the relationship between temperature and development rate for all life stages of EAB, so that we can predict how the beetle will perform in the cooler climate of the UK and western Canada. We will establish these relationships through a series of experimentsin which the different stages of the beetles are reared across a range of temperatures (7-30°C), and on different Ash tree species suspected to vary in their resistance to EAB. The data obtained will then be used to construct phenological and population models to assess the likelihood of establishment in the UK, northern Europe, and western Canada, as well as its potential rate of increase and spread, and likely impact on forest health. These models in turn will provide a basis for assessing the future economic impacts of EAB and an indication of the resources likely to be required in the future to deal with an introduction and subsequent outbreak. Understanding the potential rate of increase and spread into these new areas would enable hypotheses to be tested comparing different management strategies.
Experimental research will be conducted by the PhD student at the Natural Resources Canada Canadian Forest Service’s Great Lakes Forestry Centre (GLFC) in Sault Ste. Marie, Ontario, Canada; other studentship requirements will be fulfilled at the Faculty of Forestry, University of Toronto. There will also be the opportunity to visit ongoing Forest Research programs in the UK. Supervision will be provided by Dr Chris MacQuarrie (GLFC), Dr Daegan Inward (Forest Research, UK), and Professor Sandy M. Smith (University of Toronto).
Applications will be accepted up until December 2017, but Interested students are strongly encouraged to contact project leaders as soon as possible to discuss an earlier start date. Contacts include: Prof. Sandy M Smith, Faculty of Forestry, University of Toronto (firstname.lastname@example.org), Dr. Chris MacQuarrie, Canadian Forest Service, Sault Ste Marie (email@example.com) or Dr. Daegan Inward, UK Forest Commission (Daegan.Inward@forestry.gsi.gov.uk).
Information on the formal application process and guaranteed stipend support for PhD programs at the Faculty of Forestry can be found at: http://forestry.utoronto.ca/phd-degree-requirements/and http://forestry.utoronto.ca/phd-and-mscf-funding/. Additional information for the University of Toronto graduate school is available at: https://www.sgs.utoronto.ca/prospectivestudents/Pages/Frequently-Asked-Questions.aspx.