Freia Bladon

Email: freia.bladon@forestry.gsi.gov.uk

Tel: +44 (0)1420 22255
Tel direct: +44 (0)1420 526263

Contact address:
Tree Health Division
Forest Research
Alice Holt Lodge
Farnham
Surrey GU10 4LK
UK

Academic Career:

2006 - present
PhD: The impact of defoliating insects in a changing forest environment
Supervisors: Nigel Straw (Forest Research) and Keith Day (UU)
Studentship: Department of Employment & Learning CAST

2005 – 2006
MSc: Forest Protection and Conservation, Imperial College of Science Technology and Medicine, Silwood Park

2004 – 2005
Editorial Assistant: Current Science Group, London

2001 – 2004
BSc: Biology, Imperial College of Science Technology and Medicine, London

Outline of Current Research:

The impact of defoliating insects in a changing forest environment

Current policy objectives for UK forestry include the development of alternative silvicultural systems, maintenance of biodiversity in managed forests and protection of trees against pests and diseases. Central to this strategy is the conversion of a high proportion of commercial plantations currently managed on an intensive clear-fell and restock basis to low input, continuous cover forestry (CCF) systems. The transformation of even-aged plantations to CCF, and their subsequent maintenance, relies on the retention of a matrix of mature trees (over 50 years old) to act as a seed source for natural regeneration. However, there may be a substantial problem with this approach – field observations and tree physiology theory suggest that large mature seed trees retained in CCF systems may be more susceptible to defoliating insects and less tolerant of damage.

Sitka spruce (Picea sitchensis) is the most widely planted and commercially important tree species in the UK. A serious defoliating pest of Sitka spruce in north-west Europe is the green spruce aphid (Elatobium abietinum), and in these regions, E. abietinum frequently causes substantial needle loss to commercial plantations, leading to a significant decrease in Sitka spruce productivity. It is also one of the major forest pests thought likely to become more of a problem in the future as a result of climate change. Field observations have suggested that large mature Sitka spruce is particularly heavily attacked by E. abietinum, which raises concerns over the strategy of retaining larger trees within CCF systems, if insect attack is increased.

There are a number of reasons why, in theory, insect performance and tolerance to damage might change as trees grow older and increase in size; there are likely to be differences in the structure of the canopy, the ratio of photosynthetic to structural tissues, and the ability to store nutrients. Other factors such as foliage nitrogen content, natural enemy composition, and microclimate (temperature, light levels etc) are also likely to influence insect herbivore performance and impact in different aged forest trees.

Research Objectives:

This research project focuses on the impact and abundance of E. abietinum in traditional and CCF forest stands, and seeks to answer the question of whether large mature trees within these systems really are more susceptible to infestation and damage. The main aims of the project are:

• To compare aphid performance and populations on trees of different ages, in even-aged and mixed-aged forest stands.
  

• To identify the most important factors (e.g. tree susceptibility, microclimate, natural enemies) responsible for variation in aphid infestation and damage within the study system.