What are we looking out for?
There are hundreds of pests and diseases that are a potential threat to UK trees.
The Government has created the UK Plant Health Risk Register which records and rates risks to UK trees (and other plants) from pests and diseases.
Working with the UK Plant Health Risk Group (the group that maintains the UK Plant Health Risk Register), Observatree has identified those pests and diseases which are of the highest concern using the following criteria:
- are most likely to arrive in the UK
- have already arrived and we are concerned about their spread
- have the potential to cause the most serious and widespread impact on commercial forestry, amenity woodland and ecological systems
Below are the pests and diseases we are most keen to hear about. If you think you have spotted any of their signs, please report them using Tree Alert.
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Pests and diseases
Acute oak decline
Affects mature oak trees across the UK. Thought to be caused by a bacterium causing oozing of dark fluid from cracks in the bark.
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Pests and diseases
Asian Longhorn Beetle
Native to Eastern China, Japan and Korea, this beetle can infest a wide variety of trees with beetles emerging from spring onwards.
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Pests and diseases
Beech Leaf Disease
Beech leaf disease is a newly described disease causing discolouration of beech leaves.
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Pests and diseases
Bronze Birch Borer
Native to North America, this wood boring bupestrid beetle is a serious pest to birch trees.
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Pests and diseases
Chalara Dieback of Ash
A chronic fungal disease believed to have originated in Asia, now widespread across Europe.
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Pests and diseases
Citrus Longhorn Beetle
A non-native pest which is extremely damaging to a wide range of broadleaved trees and shrubs.
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Pests and diseases
Dothistroma Needle Blight
Widespread across the UK, this fungal disease causes needles to develop yellow and tan spots and could have a serious impact on our Scots pines.
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Pests and diseases
Elm Zigzag Sawfly
Elm zigzag sawfly larvae can defoliate whole elm trees leaving them vulnerable to further attack.
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Pests and diseases
Emerald Ash Borer
Native to Asia and Eastern Russia, the emerald ash borer is a threat to our already vulnerable ash trees.
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Pests and diseases
Great Spruce Bark Beetle
Accidentally introduced to the UK in 1982, the great spruce bark beetle damages spruce trees by tunneling into their bark.
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Pests and diseases
Horse Chestnut Leaf Miner
First observed in Macedonia and now widespread across Europe, the larvae of the horse chestnut leaf miner bores within the leaves.
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Pests and diseases
Mountain Ash Ringspot
First recorded in 1960, mountain ash ringspot is a virus that infects rowan trees and can lead to gradual dieback of the tree.
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Pests and diseases
Oak Lace Bug
The oak lace bug is a sap feeding insect, feeding on the underside of oak leaves causing them to lose their green colour. This can reduce growth and weaken the tree.
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Pests and diseases
Oak Processionary Moth
The oak processionary moth defoliate oak trees and can cause rashes and breathing difficulties in humans.
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Pests and diseases
Oriental Chestnut Gall Wasp
The oriental chestnut gall wasp larvae cause galls to develop on the buds, leaves and leaf stalks of sweet chestnut trees making them vulnerable to other pests and diseases.
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Pests and diseases
Phytophthora austrocedri
First found in the UK in 2011, Phytophthora austrocedri is a fungus-like plant pathogen that can infect and kill juniper.
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Pests and diseases
Phytophthora lateralis
Discovered in the UK in 2010, Phytophthora lateralis is a fungus-like plant pathogen that attacks the roots of Lawson cypress trees.
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Pests and diseases
Pine Processionary Moth
Pine processionary moth caterpillars can rapidly strip pine trees of their needles. There are fears it’s heading to the UK.
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Pests and diseases
Plane Lace Bug
The plane lace bug feeds only on plane trees, laying its eggs on the underside of its leaves.
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Pests and diseases
Plane Wilt
Plane wilt is a fungal disease that affects plane trees. Usually fatal, plane wilt can kill trees within two to five years.
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Pests and diseases
Red-necked Longhorn Beetle
The red-necked longhorn beetle larvae tunnel and feed under the bark of trees in the Prunus genus, such as cherries and plums.
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Pests and diseases
Sirococcus tsugae
Found in several UK locations on cedar, Sirococcus tsugae causes characteristic pink dead needles and can eventually kill shoots and branches.
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Pests and diseases
Sweet Chestnut Blight
Sweet chestnut blight is a fungus that grows beneath the bark of sweet chestnut trees causing cankers that can girdle the tree.