Tree Pests and Diseases

The damage to trees, woods and forests from insect pests and diseases (fungal, bacterial, viral) is significant. All trees species have a number of associated pests and diseases, with the potential to be more or less serious in nature. However, our changing climate combined with the continuing rise in movements of goods and people between countries has increased the risk of spreading non-native pests and diseases. These pathogens can be transported in plants, plant products, packaging, wood, vehicles and luggage.

Many introduced pathogens do little harm in their native environments, where predators, environmental factors and co-evolution with their host plants keep them in check. Outside their native range, they can cause significant damage to trees and plants where limiting factors (at least initially) are not present. A single species of pathogen can damage or kill dozens of different plant species, including trees. In addition to economic losses for the forestry, timber and plant-based sectors, they can threaten woodland biodiversity, ecosystems and native species.

A number of tools and resources are now available in the UK to help manage and minimise the impact of tree pests and diseases. These include the Tree Alert reporting system and a range of guides to the most important/common tree pests and diseases, which are important for early detection and diagnosis. 

Tree Alert – Tree Pest and Disease Reporting

Forest Research has developed the Tree Alert website to gather information about the health of the nation’s trees, woodlands and forests. This information will support important tree health monitoring and surveillance work, contribute to ongoing scientific research in this field and, ultimately, support efforts to protect the nation’s trees. To make a report access Tree Alert here:

Tree Alert Page Topper


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Observatree Field Identification Guides

These guides have been produced by Observatree, a citizen science project focused on monitoring tree health. More information: Observatree website. A poster of priority tree pests and diseases is here.

Hard copies of individual identification guides can be purchased from Summerfield Books, here. These are an invaluable resource for professional foresters and arboriculturists. 

Individual field identification guides can be downloaded here (click on the cover images to open in a new window to download directly from the Observatree website): 

European mountain ash ringspot associated virus

Mountain ash ringspot

Horse chestnut leaf miner

Horse chestnut leaf miner

Bronze birch borer

Bronze birch borer

Great spruce bark beetle

Great spruce bark beetle

Red-necked longhorn beetle

Red-necked longhorn beetle

Asian and citrus longhorn beetles

Asian and citrus longhorn beetles

Phytophthora lateralis

Phytophthora lateralis

Phytophthora austrocedri

Phytophthora austrocedri

Chestnut blight

Chestnut blight

Sirococcus tsugae

Sirococcus tsugae

Emerald ash borer

Emerald ash borer

Oak lace bug

Oak lace bug

Plane lace bug

Plane lace bug

Plane wilt

Plane wilt

Pine processionary moth

Pine processionary moth

Oak processionary moth

Oak processionary moth

Acute oak decline

Acute oak decline

Chalara ash dieback

Chalara ash dieback

Dothistroma needle blight

Dothistroma needle blight

Oriental chestnut gall wasp

Oriental chestnut gall wasp

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