Residents are being urged by Huntingdonshire District Council’s tree specialist not to cut down their horse chestnut trees if they appear to be dying or in poor condition this summer. Although the tree may appear to be dying, it is more likely to be in the midst of a severe, but not fatal disease.

Horse chestnuts are being attacked by a pest that can cause the trees to lose many of their leaves in late summer. Far from being dead, the trees are probably still healthy.

The premature leaf loss is a result of three main disorders spreading and affecting Horse Chestnut trees throughout England and Wales.

One is the Horse chestnut leaf-mining moth - Cameraria ohridella. New to Britain, this pest is now widespread in much of England and is spreading into Wales. Small adult moths lay eggs on the foliage. After hatching, the tiny caterpillars enter the leaves and eat the internal tissues. There are three generations during each summer, and so by August the foliage may be extensively damaged, leading to early leaf fall.  There is no evidence from Europe that trees have died or shown a progressive decline in health as a direct consequence of an attack.  This disease only affects the leaves of the trees.

The second is the Horse Chestnut Bleeding Canker - Pseudomonas syringae. This is a serious bacterial disease that causes bark death, canopy thinning, dieback, and often, complete death of the tree in certain species of horse chestnut. The disease starts with the development of patches on the trunk, which range from rusty-red to yellow-brown and black.

And finally the Guignardia Leaf Blotch - Guignardia aesculi. The disease is recognisable by the reddish or dull brown, irregular blotches that are often concentrated at the tips and margins of infected leaves.
This disease only affects the leaves of the trees, subsequently reducing their photosynthetic ability during the growing season. 

Brian Ogden, Arboricultural Officer at the district council said; “During the summer months a number of concerned residents have contacted Huntingdonshire District Council wondering why leaves on Horse Chestnut trees are withering and are looking under the weather. The worry is that people will think the trees are dying and have them felled, when there might be no need. Infected trees may survive for many years as disease progression can be very slow or even cease. There is certainly no need for panic tree felling. If anyone is concerned please seek further advice. “ 

Residents can help reduce the spread of the disease by disposing of leaves during the autumn and winter and then composting them thoroughly.

The council would recommend that specific advice is obtained from a suitably qualified and experienced arboriculturalist, a list can be found at the website of the Arboricultural Association which can be accessed using the link on the right.