There are several diseases that affect the horse chestnut, of which the most serious is known from its symptoms as “bleeding canker”. Bleeding canker can have a number of causes, but the recent upsurge in prevalence of the disease appears to be associated with a bacterium (Pseudomonas syringae) although this has yet to be fully confirmed by the scientists working on it. The increase in disease has been noted in France, Belgium, Germany and the Netherlands as well as Britain. Research into it is being led by scientists in the Netherlands. Though not necessarily fatal to infected trees, this is a widespread and serious disease. In common with other European countries, we are studying it to learn more about its origins, its impacts, and whether there are methods by which owners of trees could prevent or control infection.
We are also monitoring an insect pest, the horse chestnut leaf miner, which is present in southern Britain. This moth has spread across Europe since the late 1970s and appeared in Britain in 2002. Its larvae feed inside leaves with heavy infestations causing shrivelling and falling of leaves. We have no reports from Britain, or elsewhere, that it causes fatal damage on its own. As with bleeding canker, our scientists are in close touch with colleagues across Europe who are investigating this pest.
Advice to tree and woodland owners and managers on these and other pests and diseases is available on the Forestry Commission's Forest Research website http://www.forestresearch.gov.uk.