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Arboricultural consulting Tree health problems

Early detection of diseases and infestations affecting trees is key to decreasing the threat to large swathes of tree stocks. Thomson Ecology’s arboriculture team provides a full diagnosis of tree health problems, and offers advice and solutions for how pest and disease issues can be dealt with. Some current issues are highlighted below:

Ash dieback

Since large numbers of ash trees were reported to be dying from this newly identified pathogen in Poland in 1992, cases have now been widely discovered across Europe, including the UK (confirmed early 2012). The disease, which is caused by the fungus Chalara fraxinea, causes leaf loss and dieback of the crown which often ultimately leads to death of the tree. Now regarded as a quarantine pathogen, landowners are encouraged to report possible cases to the Forestry Commission or FERA in order to slow the spread of the disease. However, the loss of many ash trees in continental Europe suggests that this problem could have a major impact on the landscape in the coming years.

Dothistroma needle blight

This fungal pathogen is currently causing major problems in pine plantations, particularly those of Corsican pine (Pinus nigra var. laricio). It affects the needles, limiting the photosynthetic capacity of the trees and resulting in die-back of the crown and potential tree death. Plantations in Scotland and Thetford Forest are among the areas to be affected so far.

Emerald ash borer

A major pest in the USA, this invasive moth species from Asia causes fatal damage to members of the Fraxinus (ash) genus by boring into shoots and stems, often ‘ring barking’ trees. It is hoped that the stringent vetting of wood and plants imported into the UK will prevent it from becoming established.

Horse chestnut leaf miner

Previously thought of as only a superficial pest of the horse chestnut (Aesculus hippocastanum), it has now been shown that this moth can seriously inhibit growth. Its larvae cause extensive mining damage to foliage, which reduces the photosynthetic capacity of the trees. The cumulative effect of this and other diseases, such as the bacterial blight (Pseudomonas syringae pv. aesculi), makes for a bleak outlook for the horse chestnut.

Oak processionary moth

Currently confined to the Richmond area of West London, the Oak Processionary Moth could become a major problem if it manages to spread. As well as being a defoliator of several oak species, including our two native oaks, the tiny irritant hairs that the moth ejects when threatened can cause serious health problems.

Sudden oak death

This fungus-like pathogen of woody plant species has killed thousands of oak trees in the USA but has so far not been found to affect either of the two native oak species in the UK. However, it is currently established in the west of England and in Wales, where it is affecting Japanese larch (Larix kaempferi) plantations and Rhododendron ponticum. A sanitation felling and transportation control program is being employed by the government in an effort to halt the spread.