Threats

This page highlights the highest priority pests, including pathogens, to plants in Scottish natural environments, and signposts resources from reliable sources for identifying, controlling, and reporting them.

 

About This Page

All plants are affected by disease-causing organisms. Damage from diseases is often limited and is a natural part of habitat and host plant ecology. However, increasing global movement of plants and plant products has been accompanied by the effects of introduced pests and pathogens that are not native to Scottish habitats. These organisms find Scottish plant hosts without evolved defences, and can therefore cause major epidemics and ecological damage. Likewise, land use or climate change can increase plant susceptibility and allow native pests to become more damaging. A series of pests that can be considered threats to the Scottish natural environment are listed here.

 

The list comprises 1) selected long-present or native species that can cause significant damage in plant communities; 2) pests in the UK Pest Risk Register (PRR), already present in the UK, that affect the major genera of woody plants in Scotland; 3) PRA-listed species not yet present but that have been identified as at high risk of arrival and a high impact. In order to identify threat organisms in these habitats, searches can be based on threats to watch out for in a particular habitat, the threats likely to affect a given host, or by the threat itself. Please click through to the information sources for detailed descriptions.

 

Plant communities occurring in Scotland have been determined using the JNCC National Vegetation Classification (NVC) and the significant native tree and shrub hosts (including long term naturalised trees e.g. Sycamore and Horse chestnut) in these habitats are listed. The habitats have been grouped functionally according to the BAP Broad Habitat types in which those NVC plant communities are most frequently encountered. Note that some hosts and habitats are listed that at present have no known major threats! These are important species and habitats, and information will be added as it becomes known.

Getting Started

  1. Determine the general cause and the extent of the disease symptoms. Look for insect damage such as leaf galls or insect exit holes in the bark, or for signs of fungi or other organisms such as leaf spots or brackets on trunks of living trees. Note that some damage can be caused by abiotic factors (such as frost).

  2. Use Recommended Sources to try to identify the causal organism and to determine if it is a common and or/native species, and whether it is disease-causing or just a saprophyte (living off a dead plant that something else has killed)*.

  3. Search this page by 'Host' for diseases on the Pest Risk Register to find links to detailed information on some of the most important threats and to determine whether you need to notify authorities.

  4. Check the Prevention – Biosecurity pages to see how to keep the disease from spreading, and the Control pages for generalised advice for non-notifiable diseases. If you are fairly sure of the pests's identity, check specific resources for targeted recommendations. In the case of notifiable diseases, notify authorities and follow their instructions.

  5. Recall that these pages highlight the biggest threats to plants in the Scottish natural environment, but there are many more diseases than listed here! If you do not find a description in these pages that matches the pest you see, you can follow general Prevention – Biosecurity and Control guidance. You can also try to find the exact cause through Self Diagnosis in Recommended Sources.

Reporting Notifiable Pests

Most pests encountered will not be notifiable, but if after checking diagnostic and specific resources you think you may have encountered a notifiable pest it is important that you report it quickly. In forest trees in Scotland notify Scottish Forestry via TreeAlert or by email, or if in any other plants notify the Horticulture and Marketing Unit at SASA. Outwith Scotland consult the Plant Health Information Portal for other UK reporting contacts.

Disease Agent Habitat Type Host Information Control

Acute Oak Decline

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Quercus (Oak)

NOTIFIABLE SYNDROME

Forest Research fact sheet

Forest Research fact page

Forest Research poster

James Hutton Institute ecological impacts

Observatree fact page

RHS fact page

Woodland Trust fact page

 

Alder Rust (Melampsoridium hiratsukanum)

  • Broadleaved, mixed and yew woodland
  • Alnus (Alder)
  • Betula (Birch)

NOBANIS – Invasive Alien Species Fact Sheet

Ash Dieback (Hymenoscyphus fraxineus)

  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Fraxinus (Ash)

NOTIFIABLE ORGANISM if found in previously unconfirmed area

Observatree fact page

Observatree Toolkit

Forestry Commission fact page

Forest Research poster

Forest Research fact sheet

James Hutton Institute ecological impacts

RHS fact page

The Tree Council Ash Dieback Toolkit

 

Asian Longhorn Beetle (Anoplophora glabripennis)

  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Rivers and streams
  • Standing open water and canals
  • Supralittoral rock
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Betula (Birch)
  • Populus (Poplar, Aspen)
  • Salix (Willow)

NOTIFIABLE ORGANISM

Forest Research fact page

Opal fact page

Observatree fact page

RHS fact page

Woodland Trust fact page

 

Black Timber Bark Beetle (Xylosandrus germanus)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Rivers and streams
  • Standing open water and canals
  • Supralittoral rock
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Alnus (Alder)
  • Betula (Birch)
  • Carpinus (Hornbeam)
  • Castanea (Sweet Chestnut)
  • Fraxinus (Ash)
  • Pine (Pinus)
  • Populus (Poplar, Aspen)
  • Prunus (Blackthorn, Damson)
  • Quercus (Oak)
  • Salix (Willow)
  • Ulmus (Elm)

CABI data sheet

Natural Resources Canada fact page

Bronze Birch Borer (Agrilus anxius)

  • Bogs
  • Boundary and linear features
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Dwarf shrub heath
  • Inland rock
  • Betula (Birch)

NOTIFIABLE ORGANISM

DAERA fact page

Observatree fact page

Canker of Conifers (Gremmeniella abietina)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

CABI data sheet

CIFA fact sheet

Chestnut Blight (Cryphonectria parasitica)

  • Broadleaved, mixed and yew woodland
  • Castanea (Sweet Chestnut)

NOTIFIABLE ORGANISM

CABI data sheet

Forest Research fact page

Woodland Trust fact page

Observatree fact page

Citrus Longhorn Beetle (Anoplophora chinensis)

  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Rivers and streams
  • Standing open water and canals
  • Supralittoral rock
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Aesculus (Horse Chestnut)
  • Alnus (Alder)
  • Betula (Birch)
  • Carpinus (Hornbeam)
  • Corylus (Hazel)
  • Crataegus (Hawthorn)
  • Fagus (Beech)
  • Malus (Apple)
  • Populus (Poplar, Aspen)
  • Prunus (Blackthorn, Damson)
  • Rose (Rosa)
  • Salix (Willow)
  • Ulmus (Elm)

NOTIFIABLE ORGANISM

DEFRA fact sheet

NRW fact page

NNSS fact page

Observatree fact page

OPAL fact page

RHS fact page

Scottish Government fact page

Conifer Root and Butt Rot (Heterobasidium annosum)

  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Pine (Pinus)

Forest Research fact page

First Nature fact page

Dothistroma Needle Blight (Dothistroma septosporum)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

Forest Research field guide

Forestry Commission fact sheet

Forest Research poster

Forest Research fact page

Observatree fact page

Woodland Trust fact page

Dutch Elm Disease (Ophiostoma novo-ulmi)

  • Broadleaved, mixed and yew woodland
  • Ulmus (Elm)

Forest Research fact page

Forest Research fact sheet

Forest Research pathology note

Forestry Commission Research Information Note 252

RHS fact page

Elm Zig Zag Sawfly (Aproceros leucopoda)

  • Broadleaved, mixed and yew woodland
  • Ulmus (Elm)

Forest Research fact page

Emerald Ash Borer (Agrilus planipennis)

  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Fraxinus (Ash)

NOTIFIABLE ORGANISM

Forest Research fact page

Observatree fact page

Woodland Trust fact page

DAERA fact page

EAB Information network

Fire Blight (Erwinia amylovora)

  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Coniferous woodland
  • Inland rock
  • Montane habitats
  • Crataegus (Hawthorn)
  • Malus (Apple)
  • Prunus (Blackthorn, Damson)
  • Rose (Rosa)
  • Rubus (Blackberry)
  • Sorbus (Rowan)

NOTIFIABLE ORGANISM

RHS fact page

CABI data sheet

 

Golden Root Mealy Bug (Chryseococcus arecae)

  • Acid grassland
  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Improved grassland
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Neutral grassland
  • Supralittoral rock
  • Supralittoral sediment
  • Primula (Primrose)
  • Erica (Heath)

RHS fact page

Great Spruce Bark Beetle (Dendroctonus micans)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

CABI data sheet

Forestry Commission fact sheet

Forest Research pest management fact page

NRW fact page

Observatree fact sheet

Observatree fact page

 

Gypsy Moth (Lymantria dispar)

  • Acid grassland
  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Rivers and streams
  • Standing open water and canals
  • Supralittoral rock
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Betula (Birch)
  • Malus (Apple)
  • Prunus (Blackthorn, Damson)
  • Quercus (Oak)
  • Salix (Willow)
  • Ulmus (Elm)

Forest Research fact page

Honey fungus (Armillaria spp)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Fen, marsh and swamp
  • Inland rock
  • Littoral sediment
  • Montane habitats
  • Rivers and streams
  • Standing open water and canals
  • Supralittoral rock
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Aesculus (Horse Chestnut)
  • Betula (Birch)
  • Fagus (Beech)
  • Ilex (Holly)
  • Malus (Apple)
  • Pine (Pinus)
  • Prunus (Blackthorn, Damson)
  • Quercus (Oak)
  • Rose (Rosa)
  • Salix (Willow)
  • Sorbus (Rowan)

Forestry Commission fact sheet

RHS fact page

First Nature fact page

 

Horse Chestnut Bleeding Canker (Pseudomonas syringae pv. aesculi)

  • Broadleaved, mixed and yew woodland
  • Aesculus (Horse Chestnut)

Forest Research fact page

Forestry Commission fact sheet

RHS fact page

Woodland Trust fact page

Horse Chestnut Leaf Miner (Cameraria ohridella)

  • Broadleaved, mixed and yew woodland
  • Aesculus (Horse Chestnut)

Forestry Commission fact page

Observatree fact page

RHS fact page

Woodland Trust fact page

Large Brown Pine Weevil (Hylobius abietis)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

Forest Research fact page

Forestry Commission fact page

CABI data sheet

Larger Eight-toothed European Spruce Bark Beetle (Ips typographus)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

NOTIFIABLE ORGANISM

Forestry Commission fact sheet

DAERA fact page

CABI data sheet

Lophodermium Needle Cast (Lophodermium seditiosum)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

Cornell University fact page

Diseases and Disorders of Forest Trees (by S.C. Gregory and D.B. Redfern, 1998, Forestry Commission Field Book 16 )

Forest Pests fact page

University of Massachusetts Amherst fact page

Nematodes

  • Boundary and linear features
  • Broadleaved, mixed and yew woodland
  • Malus (Apple)
  • Pine (Pinus)

Pine wood nematode is a NOTIFIABLE ORGANISM

Plantwise Knowledge Bank fact page (Dagger nematode)

University of Florida fact page (Dagger nematode)

Forestry Commission fact page (Pine wood nematode)

Oak Pinhole Borer (Platypus cylindrus)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Castanea (Sweet Chestnut)
  • Fagus (Beech)
  • Fraxinus (Ash)
  • Quercus (Oak)
  • Ulmus (Elm)

Forest Research fact page

Forest Research fact sheet

Oak Processionary Moth (Thaumetopoea processionea)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Quercus (Oak)

NOTIFIABLE ORGANISM

CABI data sheet

Forest Research advice note

Forest Research fact page

Forest Research poster

Observatree fact page

Woodland Trust fact page

Oak Wilt (Ceratocystis fagacearum)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Quercus (Oak)

NOTIFIABLE ORGANISM

DAERA fact page

Forestry Commission fact page

NRCS fact sheet

Oriental Chestnut Gall Wasp (Dryocosmus kuriphilus)

  • Broadleaved, mixed and yew woodland
  • Castanea (Sweet Chestnut)

NOTIFIABLE ORGANISM

Observatree fact page

Observatree toolkit

Forestry Commission poster

Royal Forestry Society article

Phytophthora alni

  • Broadleaved, mixed and yew woodland
  • Alnus (Alder)

Forest Research fact page

Forestry Commission fact sheet

Phytophthora austrocedri

  • Bogs
  • Boundary and linear features
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Dwarf shrub heath
  • Montane habitats
  • Supralittoral rock
  • Juniperus (Juniper)

NOTIFIABLE ORGANISM

Forest Research fact page

Forest Research fact sheet

Forestry Commission fact page

Observatree fact page

 

Phytophthora pseudosyringae

  • Acid grassland
  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Inland rock
  • Montane habitats
  • Supralittoral sediment
  • Quercus (Oak)
  • Vaccinium (Bilberry, Cowberry)
  • Tilia (Lime)
  • Malus (Apple)
  • Carpinus (Hornbeam)
  • Alnus (Alder)
  • Castanea (Sweet Chestnut)
  • Fagus (Beech)
  • Acer (Maple, Sycamore)

Forestry Research fact page

Phytophthora ramorum/kernoviae

  • Acid grassland
  • Bogs
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Calcareous grassland
  • Coniferous woodland
  • Dwarf shrub heath
  • Inland rock
  • Montane habitats
  • Supralittoral sediment
  • Acer (Maple, Sycamore)
  • Aesculus (Horse Chestnut)
  • Arctostaphylos (Bearberry)
  • Castanea (Sweet Chestnut)
  • Fagus (Beech)
  • Quercus (Oak)
  • Vaccinium (Bilberry, Cowberry)

NOTIFIABLE ORGANISM

DEFRA fact sheet (Vaccinium symptoms)

DEFRA fact sheet (Vaccinium)

DEFRA fact sheet (P. kernoviae)

DEFRA fact sheet (P. ramorum)

DEFRA fact sheet (parks)

Forest Research fact page (P. ramorum)

Forestry Commission fact page (P. kernoviae)

RHS fact page

 

 

Phytophthora rubi

  • Bogs
  • Boundary and linear features
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Rubus (Blackberry)

Pacific North West Pest Management Handbook fact page

Phytophthora siskiyouensis

  • Broadleaved, mixed and yew woodland
  • Alnus (Alder)

NOTIFIABLE ORGANISM

New Disease Report

Phytoplasmas

  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Improved grassland
  • Inland rock
  • Neutral grassland
  • Supralittoral sediment
  • Malus (Apple)
  • Populus (Poplar, Aspen)
  • Primula (Primrose)
  • Prunus (Blackthorn, Damson)
  • Rose (Rosa)
  • Tilia (Lime)
  • Ulmus (Elm)

Elm Yellows Phytoplasma is a NOTIFIABLE ORGANISM

Plantwise Knowledge Bank Fact Sheet Search (by phytoplasma name)

CABI Invasive Species Compendium Search (by phytoplasma name)

DEFRA fact page (Yellow Disease Phytoplasmas Phytoplasma asteris)

DEFRA fact sheet (Pear Decline Phytoplasma - Phytoplasma pyri)

Forestry Commission fact sheet (Elm Yellows Phytoplasma  - Phytoplasma ulmi)

Forestry Commission fact page (Elm Yellows Phytoplasma  - Phytoplasma ulmi)

Pine Lappet Moth (Dendrolimus pini)

  • Bogs
  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Montane habitats
  • Pine (Pinus)

NOTIFIABLE ORGANISM

Forest Research fact sheet

Forestry Commission fact page

Pine Pitch Canker (Fusarium circinatum)

  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Pine (Pinus)

NOTIFIABLE ORGANISM

Forestry Commission fact page

Forestry Commission fact sheet

Pine Processionary Moth (Thaumetopoea pityocampa)

  • Broadleaved, mixed and yew woodland
  • Coniferous woodland
  • Pine (Pinus)

NOTIFIABLE ORGANISM

Forestry Commission fact page

Forestry Commission fact sheet

Forestry Commission poster

IMPACT fact sheet

Observatree fact page

OPAL fact page

Poplar Canker (Entoleuca mammata)

  • Broadleaved, mixed and yew woodland
  • Populus (Poplar, Aspen)

USDA fact sheet

Natural Resources Canada fact page

Viruses

  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Calcareous grassland
  • Coniferous woodland
  • Improved grassland
  • Inland rock
  • Neutral grassland
  • Supralittoral sediment
  • Primula (Primrose)
  • Prunus (Blackthorn, Damson)
  • Rose (Rosa)
  • Sorbus (Rowan)

Rose Rosette Virus and Tomato Black Ring Viruses are NOTIFIABLE ORGANISMS

Plantwise Knowledge Bank Fact Sheet Search (by virus name)

CABI Invasive Species Compendium Search (by virus name)

DEFRA fact sheet (Rose Rosette Virus - Rosa)

CABI fact page (Tomato Black Ring Virus - Prunus)

CERIS Purdue University fact sheet (Tomato Black Ring Virus - Prunus)

Observatree fact page (European Mountain Ash Ringspot Associate Virus)

Observatree guide (European Mountain Ash Ringspot Associate Virus)

FERA fact sheet (European Mountain Ash Ringspot Associate Virus)

RHS fact page (Impatiens necrotic spot virus - Primula)

DEFRA fact sheet (Plum Pox Virus - Prunus)

CABI fact page (Prunus Necrotic Ringspot Virus - Prunus, Rosa)

PNW Handbook fact page (Prunus Necrotic Ringspot Virus - Prunus, Rosa)

CABI fact page (Raspberry Ringspot Virus - Prunus)

CABI fact page (Tomato Ringspot Virus - Prunus)

PNW Handbook fact page (Arabis Mosaic virus - Rosa)

CABI fact page (Strawberry Latent Ringspot Virus - Rosa)

Xylella (Xylella fastidiosa)

  • Acid grassland
  • Boundary and linear features
  • Bracken
  • Broadleaved, mixed and yew woodland
  • Built up areas and gardens
  • Quercus (Oak)
  • Ulmus (Elm)

NOTIFIABLE ORGANISM

Forestry Commission fact page

Forestry Commission pest alert

DEFRA fact page