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Forest Diary - April

Be Tree Alert!

by Esta Mion, Communications Manager at Forestry Commission

 Spring has finally sprung in the New Forest, a little later than we had perhaps hoped, but there have even been glimpses of summer just around t he corner.

However, the fresh green leaves and shoots which bring such hope can sometimes harbour the first signs of distress in our trees. Britain’s trees are under continued threat from pests and diseases. Over the past few years in the New Forest, our foresters and planners have been dealing with emerging issues such as Dothistroma Needle Blight (DNB): Dothistroma septosporum (Dothistroma Needle Blight) which is a non-native pathogen.

It’s found in many forests, including the New Forest, affecting key pine species, including Corsican pine, lodgepole pine and more recently Scots pine. The presence of the disease in some Caledonian pine forests in Scotland could pose a significant risk to this iconic resource, which has an important landscape, biodiversity and heritage value.

As the disease is now widely established in Great Britain, an extensive programme of government-funded research is underway to help protect pine species and reduce impacts of the disease.


Ash trees have also become a great cause for concern for many woodland managers in recent years with the challenges of dealing with a disease called Chalara dieback of ash (Chalara fraxinea). This disease causes leaf loss, crown dieback and bark lesions in affected trees. Once a tree is infected the disease is usually fatal, either directly, or indirectly by weakening the tree to the point where it succumbs more readily to attacks by other pests or pathogens, especially Armillaria fungi, or honey fungus.

Since Ash Dieback arrived in 2012, our teams locally have been on the ground surveying the South Forest District’s ash trees for further signs of the disease. Fortunately, here in the New Forest, ash trees make up a very small proportion of trees found here, 0.2%.  Spring is not the easiest time to recognise symptoms of Chalara dieback, and it might be some time before it is obvious on the leaves.

You can help by looking out for the symptoms on local ash trees and reporting suspected cases to us with the ‘Tree Alert’ reporting tool on our website. We especially want reports of cases in areas where it has not already been found, and people can find out whether the disease is already in their local area from the maps on our website at


People can also keep an eye on specific ash trees in their areas, and if any appear to remain healthy while others nearby get the disease, let The Living Ash Project know. The project is monitoring apparently tolerant trees across the UK so that they can be used for breeding tolerant ash trees for the future.

There’s lots of information on our website, which explains how to look for and recognise signs of the disease on new growth and older branches. Ash trees come into leaf later than most other trees, and the timing can vary according to where they are and the particular species of ash. So if an ash tree does not have any leaves on it right now, it does not necessarily mean that it is diseased or dying. However, all healthy ash should be in full leaf by mid-June. 

Some shoots on ash trees won’t produce leaves at all, while others will behave normally before showing signs of ill-health or dieback. These signs might mean that the trees are damaged in some way, but shoot death and dieback in ash trees can have a number of causes. 

August and September are the best months to look for symptoms in the leaves, because by autumn infected leaves can be confused with leaves that are naturally changing colour.

Our extensive UK surveillance programme involves government, industry, conservation groups and the public. It includes aerial photography; the ‘Observatree’ network of volunteer tree health surveyors trained by Forest Research and the Woodland Trust; and inspections at nurseries and retail sites to detect any issues at an early stage.

When you’re out and about, visiting woodlands, parks and gardens, you can help limit the spread of plant diseases between places by washing mud and leaves off your bikes, buggies and boots between visits.

Further information about ash dieback including a map of confirmed locations, and access to Tree Alert are available at

For more information about the Forestry Commission in the New Forest, visit


Last updated: 21st April 2018


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England's Woods and Forests are cared for by Forest Enterprise England, an agency of the Forestry Commission.