Summary

This programme carries out research on a number of insect pests that cause defoliation or other types of non-lethal injury to forest trees. The objective is to determine the impact of these insects on tree growth and timber production, and to estimate the economic costs of damage.

The most detailed research has focussed on the impact of green spruce aphid (Elatobium abietinum) on Sitka spruce. Long-term experiments on the effect of defoliation by this aphid on young Sitka spruce were undertaken in Hafren Forest, Wales, during 1993-2000, and comparative work on mid-rotation Sitka spruce is currently being undertaken in Radnor Forest (2000-2006). Research on the green spruce aphid is linked to the potential impacts of climate change programme, as global warming is likely to have a major influence on the prevalence of this pest.

Other current research projects include studies on the impact of horse chestnut leafminer (Cameraria ohridella), the biology and ecology of leaf weevils (Phyllobius species), and the relationship between hornet clearwing moth (Sesia apiformis) and dieback in mature poplars. Previous studies have quantified the impact of pine looper moth (Bupalus piniaria) on Scots pine, and damage caused by insects and disease to poplars and willows grown as short-rotation coppice.

Research objectives

The main objective of the programme is to quantify the effects of phytophagous insects on the growth of forest trees, and to use this information to estimate the economic costs of non-lethal damage. The main parameters used to describe growth loss are reductions in height, diameter and volume increment. However, an important part of the research is to understand the mechanisms that determine the response of trees to insect attack. This involves detailed assessment of insect populations, patterns of shoot growth, and canopy biomass, in order to establish relationships between insect densities, rates of damage and changes in tree performance.

Specific objectives:

• Determine the impact of green spruce aphid on Sitka spruce by quantifying relationships between aphid population densities, defoliation and tree height and volume increment.
• Obtain field data on populations of the green spruce aphid in relation to key climate variables (e.g. temperature, rainfall, humidity, wind speed) to determine the likely response of the aphid to climate change.
• Monitor the spread of horse chestnut leafminer in the UK and determine its impact on horse chestnut trees in urban and rural situations.
• Develop an understanding of the ecology and impact of leaf weevils in the genus Phyllobius, in particular the circumstances under which they cause significant defoliation of young broad-leaved trees.
• Investigate the long-term interactions between hornet clearwing moth and dieback and recovery in poplars.

Funders and partners

This research is funded by the Forestry Commission Alternative management approaches programme.

Research on green spruce aphid has been part funded by European Union research and development programmes AIR-3-CT94-1883 ‘The spruce aphid in Western Europe’ and FAIR-3-CT96-1792 ‘Improving protection and resistance of trees to the spruce aphid’.

Status

The programme started in April 1989 and is ongoing. Current research on green spruce aphid in Radnor Forest commenced in 1999

Impact of insects on tree growth – References

Straw, N.A., Fielding, N.J., Green, G. and Price, J. (2006). Seasonal changes in the distribution of green spruce aphid, Elatobium abietinum (Walker) (Homoptera: Aphididae) in the canopy of Sitka spruce. Agricultural and Forest Entomology 8: 139-154.

Straw, N.A. and Tubby, I. (2006). Tree mortality associated with the aphid Pterocomma populeum Kalt. in a young poplar plantation. Quarterly Journal of Forestry 100: 43–52.

Straw, N.A. and Tilbury, C. (2006). Host plants of the horse-chestnut leaf-miner (Cameraria ohridella), and the rapid spread of the moth in the UK 2002-2005. Arboricultural Journal 29: 83–99.

Straw, N.A., Fielding, N.J., Green, G. and Price, J. (2005). Defoliation and growth loss in young Sitka spruce following repeated attack by the green spruce aphid, Elatobium abietinum (Walker). Forest Ecology and Management 213: 349–368.

Williams, D.T., Straw, N. A. and Day, K.R. (2005). Performance of the green spruce aphid, Elatobium abietinum (Walker), on previously defoliated Sitka spruce. Agricultural and Forest Entomology 7: 95-105

Straw, N.A. and Bellett-Travers, M. (2004). Impact and management of the horse chestnut leaf-miner, (Cameraria ohridella). Arboricultural Journal 28: 67–83.

Williams, D.T., Straw, N.A. and Day, K.R. (2003). Defoliation of Sitka spruce by the European spruce sawfly, Gilpinia hercyniae (Hartig): a retrospective analysis using the needle trace method. Agricultural and Forest Entomology 5: 235–245.

Armour, H., Straw, N. and Day, K. (2003). Interactions between growth, herbivory and long-term foliar dynamics of Scots pine. Trees – Structure and Function 17: 70–80.

Straw, N.A., Armour, H. and Day, K. (2002). The financial costs of defoliation of Scots pine (Pinus sylvestris L.) by pine looper moth (Bupalus piniaria L.). Forestry 75: 525-–536.

Straw, N.A., Fielding, N.J., Green, G. and Price, J. (2002). The impact of green spruce aphid, Elatobium abietinum (Walker), on the growth of young Sitka spruce in Hafren Forest, Wales: delayed effects on needle size limit wood production. Forest Ecology and Management 157: 267–283.

Straw, N.A. (2002). The impact of green spruce aphid (Elatobium abietinum (Walker)) on young and mature spruce plantations. In: Protection of the World’s Forests from Insect Pests: Advances in Research, edited by Alfaro, R., Day, K., Salom, S., Nair, K.S.S., Evans, H., Liebhold, A., Lieutier, F., Wagner, M., Futai, K. and Suzuki, K., pp 29–36. IUFRO World Series, Vol. 11. IUFRO Secretariat, Vienna.

Straw, N.A. and Green, G. (2001). Interactions between green spruce aphid, Elatobium abietinum (Walker), and Norway and Sitka spruce under high and low nutrient conditions. Agricultural and Forest Entomology 3: 263–274.

Arundell, J.C. and Straw, N.A. (2001). Hornet clearwing moth (Sesia apiformis [Clerck]) and dieback of poplars in eastern England. Arboricultural Journal 25(3): 235–253.

Evans, H.F., Straw, N.A. and Watt, A.D. (2001). Climate change: implications for forest insect pests. In: Climate Change: Impacts on UK Forests, edited by Broadmeadow, M., pp.99–118. Forestry Commission Bulletin 125. Forestry Commission, Edinburgh.

Straw, N.A., Fielding, N.J., Green, G. and Price, J. (2000). The impact of green spruce aphid, Elatobium abietinum (Walker), and root aphids on the growth of young Sitka spruce in Hafren Forest, Wales: effect on height, diameter and volume. Forest Ecology and Management 134: 97–109.

Straw, N.A. and Lonsdale, D. (2000). Pest and disease monitoring. In: Short Rotation Coppice and Wood Fuel Symposium: from Research to Renewable Energy, edited by Armstrong, A. and Claridge, J., pp.23–29. Forestry Commission, Edinburgh.

Nicol, D., Armstrong, K.F., Wratten, S.D., Walsh, P.J., Straw, N.A., Cameron, C.M., Lahmann, C. and Frampton, C.M. (1998). Genetic diversity of an introduced pest, the green spruce aphid Elatobium abietinum (Hemiptera: Aphididae) in New Zealand and the United Kingdom. Bulletin of Entomological Research 88: 537-543.

Straw, N.A., Fielding, N.J., Green, G. and Coggan, A. (1998). The impact of green spruce aphid, Elatobium abietinum (Walker), on the growth of young Sitka spruce in Hafren Forest, Wales: pattern of defoliation and effect on shoot growth. Forest Ecology and Management 104: 209–225.

Straw, N.A., Halldórsson, G. and Benedikz, T. (1998). Damage sustained by individual trees: empirical studies on the impact of the green spruce aphid. In: The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management, edited by Day, K.R., Halldórsson, G., Harding, S. and Straw, N.A., pp. 15–31. Forestry Commission Technical Paper 24. Forestry Commission, Edinburgh.

Day, K.R., Straw, N.A. and Harding, S. (1998). Prospects for sustainable management of forests to minimise the green spruce aphid problem in Europe. In: The Green Spruce Aphid in Western Europe: Ecology, Status, Impacts and Prospects for Management, edited by Day, K.R., Halldórsson, G., Harding, S. and Straw, N.A., pp. 97–105. Forestry Commission Technical Paper 24. Forestry Commission, Edinburgh.

Straw, N.A. (1996). The impact of pine looper moth, Bupalus piniaria L. (Lepidoptera; Geometridae) on the growth of Scots pine in Tentsmuir Forest, Scotland. Forest Ecology and Management 87: 209–232.

Straw, N.A., Fielding, N.J. and Waters, A. (1996). Phytotoxicity of insecticides used to control aphids on Sitka spruce (Picea sitchensis (Bong.) Carr.). Crop Protection 15: 451–459.

Straw, N.A. (1995). Climate change and the impact of the green spruce aphid, Elatobium abietinum (Walker), in the UK. Scottish Forestry 49: 134–145.