Technical Update

Tree care in unsettled weather

With first drought, then extreme wet and stormy conditions threatening both newly planted and established trees, the Tree Council has come up with tips to help trees survive in unpredictable weather as part of its continuing Tree Care Campaign.

Please see our Tree Care Campaign page for more information and other tips about tree care.

Alert for serious disease of ash trees

The tree world is on the alert for any signs of a destructive fungal disease, Chalara dieback of ash, which hit the UK for the first time this year.

In particular, those involved in the plant nursery and tree-care sectors are being urged to check on the health of recently planted ash trees, and notify any symptoms that could be the result of the disease.

The appeal follows the second discovery in England of ash dieback disease caused by the fungus Chalara fraxinea (C. fraxinea), which has the potential to kill millions of ash trees if it spreads into the natural environment. It has already caused widespread losses in continental Europe, including an estimated 60 to 90 per cent of Denmark’s ash trees.

This second discovery – in June – was in young ash trees recently planted at a Leicestershire car park. This followed an interception in February by the Food & Environment Research Agency (Fera) of diseased ash plants in a shipment from a supplier in the Netherlands to a nursery in Buckinghamshire.

“This is a very worrying development. C. fraxinea is an aggressive pathogen which has the potential to inflict considerable damage on Britain’s ash trees,” said Dr John Morgan, Head of the Forestry Commission’s Plant Health Service. “Ash is a much-loved native species which is important for its timber, woodfuel, wildlife, biodiversity and landscape benefits, and it is one of our most numerous tree species.

“We have agreed with Fera to adopt a precautionary approach and to inspect ash plants in nurseries and destroy any material with this disease in order to prevent it from spreading into the natural environment. Because we now know that C. fraxinea is present in the nursery trade we expect there will be more interceptions in the near future.

“We are urging anyone who has received ash trees in the past five years to check their trees’ health and to report any suspicious symptoms to us without delay.”

The disease mostly affects common ash (Fraxinus excelsior), including its ‘Pendula’ ornamental variety, but Fraxinus angustifolia can also be infected. Deaths in continental Europe have been particularly common in saplings.

Symptoms can be visible on leaves, shoots and branches of affected trees. In severe cases, the entire crown shows leaf loss and dieback and there may also be the formation of epicormic shoots (small whiskery shoots that appear in clumps from buds) on branches and the trunk.

Further information, including more about what symptoms to look out for and how to report suspected cases go to the Forestry Commission’s website. (www.forestry.gov.uk/ashdieback)

Look out for emerging Asian long-horn beetles

Tree Wardens are urged to help prevent future outbreaks of the Asian longhorn beetle by looking out for any that are now emerging from trees and shrubs.

This follows the UK’s first outbreak of breeding beetles earlier this year in the Paddock Wood area of Kent where 67 infested trees have so far been found. As tree felling to eradicate this outbreak is nearing completion, The Food & Environment Research Agency (Fera) and the Forestry Commission are asking the public across the UK to look out for the distinctive beetles during the emergence season.

The insects’ larvae cause serious damage to trees, and can kill them, by boring tunnels in the trunks and branches as they eat their way through the wood, before emerging as mature beetles.

The main known host trees are maple, sycamore, horse chestnut, Mimosa silk tree, alder, birch, hornbeam, Katsura tree, hazel, beech, ash, golden rain tree, plane, poplar, cherry, plum, false acacia/black locust, willow, sallow, pagoda tree, mountain ash (rowan), whitebeam, American pin oak, North American red oak and elm.

The most obvious symptoms are the circular adult exit holes, which are about 10 mm (0.4 inches) in diameter. Other signs which might be present, but are much less obvious, include piles of sawdust-like droppings at the base of infested trees, scraped bark, sap bleeding from the sites where eggs have been laid, and bark-feeding damage on smaller branches and shoots.

Anyone who suspects they have seen an Asian longhorn beetle, or evidence of its presence, should telephone the Fera Plant Health Helpline on 0300 1000325, email This e-mail address is being protected from spambots. You need JavaScript enabled to view it or use the new reporting app on Fera’s website at http://albwatch.fera.defra.gov.uk. Digital photographs may be sent with email reports to aid identification.

If possible, the beetle should be caught and placed in a secure container such as a sealed glass jar so that an inspector can collect it. The beetles are harmless to humans, although they should be handled with caution because they can nip the skin.

Further information is available from www.fera.defra.gov.uk/asianlonghornbeetle and www.forestry.gov.uk/asianlonghornbeetle.