This project aims to quantify the impact of horse chestnut leaf miner (Cameraria ohridella) on the growth and health of horse chestnut trees (trees in the Aesculus genus), and to determine whether impact is increased or decreased through interactions with bleeding canker, a disease caused by the bacterial pathogen Pseudomonas syringae pv. aesculi.

Research objectives

Specific research objectives are to:

• carry out annual assessments of leaf miner infestation, tree growth and condition, and disease incidence for a selected sample of 200+ horse-chestnut trees;
• analyse trends to determine whether high rates of leaf miner damage are associated with decreases in tree growth and increases in bleeding canker;
• compare the responses of white horse-chestnut (Aesculus hippocastanum) and red horse-chestnut (Aesculus x carnea) to infestation and disease; and
• identify factors that influence the abundance of horse-chestnut leaf miner and which may assist in its management

Results so far

Data collected over the 10 years from 2002 to 2012 show that although Cameraria ohridella can damage up to 75% of the total leaf area of white horse chestnut (Aesculus hippocastanum), it has no influence on stem radial growth or general tree condition. Red horse chestnuts (Aesculus × carnea) are rarely attacked by the moth, and then only when growing close to heavily infested white horse chestnuts.

In contrast, bleeding canker disease caused the death or removal of 11% of white horse chestnuts and 27% of red horse chestnuts. Trees that were infected by the disease, but were still alive, showed a decrease in growth and a decline in crown condition.

There was no evidence that the presence of Cameraria ohridella or the damage it caused either facilitated the spread of bleeding canker disease or accentuated the impact of the disease. In fact the opposite was observed: trees with the highest rates of leaf miner infestation tended to have the lowest incidence of bleeding canker disease.

Status

This project started in 2002 and data collection has continued. An update will be published when the next 10 years’ data have been fully collected and analysed.

Related resources

• Main horse-chestnut leaf miner resources page

Related publications

D’Costa L, Koricheva K, Straw N & Simmonds M (2013) Oviposition patterns and larval damage by the invasive horse-chestnut leaf miner Cameraria ohridella on different species of Aesculus. Ecological Entomology 38, 456–462.

Pocock M., Evans D, Straw N. & Polaszek A (2011) The horse chestnut leaf miner and its parasitoids. British Wildlife 22, 305-313.

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

See also the Conker Tree Science Project.

Funders and partners

This work is funded by the Forestry Commission under the Programme of Advice and Scientific Support for Tree Health.

Forestry Commission policy
This research underpins the evidence base for the delivery of healthy and resilient forests and wider ecosystems which is part of the Tree Health and Plant Biosecurity Action Plan.