Cadw coetiroedd yn iach yng Nghymru ac Iwerddon

Ymddiheuriadau, ond nid oes cyfieithiad Cymraeg y tudalen hon ar gael. Darllenwch cyfiethiad awtomatig gan Google


On this page you will find brief profiles of some of the most important pests and pathogens affecting the forests and woodlands of Ireland and Wales. Latest methods for tackling these can be found within the RESEARCH section.


1. Horse Chestnut Leaf Miner

Scientific name: Cameraria ohridella (Deschka & Dimic, 1986)
Taxonomic position: Insecta: Lepidoptera: Gracillariidae
Common name: Horse Chestnut Leaf Miner
More details on the Horse Chestnut Leaf Miner (PDF)

Hosts: Horse Chestnut Aesculus Hippocastanum and other Aesculus species, but hybrid red flowering Horse Chestnut Aesculus x carnea is highly resistant. Also Sycamore Acer pseudoplatanus and Norway Maple A. platanoides.

Threats: Aesthetic and nuisance issues in streets, parks and gardens, but little effect on tree health and growth so far. Commercial crops of Acer species could be affected by the pest. Combination of moth damage with drought or bleeding canker could be more dangerous.

Distribution and spread: Rapid spread in Britain from first record in London in 2002 to sites across most of England and Wales. No records yet from Scotland or Ireland. Dispersal is by wind assisted flight, also accidental vehicle transport of adults or infested leaves.

Green Spruce Aphid

2. Green Spruce Aphid

Scientific name: Elatobium abietinum (Walker, 1849)
Taxonomic position: Hemiptera Aphididae
Common name: Green Spruce Aphid
More details on the Green Spruce Aphid (pdf)

Hosts: The green spruce aphid, Elatobium abietinum (Walker) defoliates Sitka Spruce in the UK. It spends all year on Picea spp., especially Sitka spruce (Picea sitchensis) and also on Norway spruce (P. abies) and Blue spruce (P. pumgens), but less commonly on Firs (Abies spp.).

Threats: The green spruce aphid is a widespread pest of Sitka and other spruces in North-West Europe. In the UK it overwinters in the adult stages, and during mild winters it will continue to feed and reproduce. The greatest damage to spruce occurs after a mild winter when it can kill off the needles by sucking the trees sap. It can cause severe damage to mature trees and saplings. Under the right weather conditions it is capable of an explosive increase, but fluctuates according to the weather conditions. In Christmas tree plantations any discolouration and loss of foliage is unacceptable and would render the trees unsaleable thus it is an economic pest.

Distribution and spread: Throughout UK wherever host species plantations of spruce are present. The geographical origin is unknown but it is native to Western Europe, and well established in western North America throughout the range of Sitka spruce from Alaska to California.

Pine weevil

3. Large Pine Weevil

Scientific name: Hylobius abietis (L) (Linnaeus, 1758)
Taxonomic position: Coleoptera, Curculionidae
Common name: Large Pine weevil
More details on the Large Pine Weevil (pdf)

Hosts: Wide range of conifer species such as: Sitka spruce (Picea sitchensis); Douglas fir (Pseudotsuga menziesii) and Scots pine (Pinus sylvestris) are more suitable than Norway spruce (Picea abies). Breed principally in stumps and roots of felled trees and adult Large Pine weevils feed on the living bark of most woody shrubs or trees.

Threats: Felling a coniferous crop produces a large increase in breeding material for the larvae, whilst plant material suitable for adult feeding is reduced. Young trees used for restocking are liable to be heavily attacked by adult pine weevils feeding on the stem from the root collar upwards. Heavy damage can completely girdle stems and cause plant death.

Distribution and spread: Widely distributed throughout UK especially Wales, Scotland and Ireland, and is the most serious pest of conifer reforestation in the UK and Ireland. It has been possible to verify that the time of year as well as the time of felling of a commercial stand of Sitka spruce (Picea sitchensis) both influences the spatial distribution and development of the Large Pine weevil. In early summer the adult pine weevil are capable of long distance migration to colonise new areas. It has been recorded in Sweden that they can travel up to 80km in extreme circumstances, but 10km is more common and will only fly when wind speeds are less than 4 m/s and temperatures above 18°C.

Great spruce bark beetle

4. Great Spruce Bark Beetle

Scientific name: Dendroctonus micans (Kugelann, 1794)
Taxonomic position: Coleoptera: Scolytidae
Common name: Great spruce bark beetle
More details on the Great Spruce Bark Beetle (pdf)

Hosts: Norway spruce (Picea abies); Scots pine (Pinus sylvestris); Larch (Larix decidua) and Fir (Picea spp.). It attacks the root and stem of plants and breeds in the bark; already damaged areas preferred. They tunnel to form galleries within the bark of living trees where their larvae feed and develop, ultimately killing the tree.

Threats: A well-established pest that was accidentally introduced from continental Europe concealed in imported timber pallets. As spruce is our most important commercial tree species managing this pest is a high priority.

Distribution and spread: First detected in Shropshire in 1982, it has since spread and became common enough to cause economic damage to forestry in Wales and parts of north-west England and Galloway, Scotland. It has not been recorded in Ireland other than as an occasional accidental import with forest products.

Asian longhorn beetle

5. Asian Longhorn Beetle

Scientific name: Anoplophora glabripennis (Motschulsky, 1853)
Taxonomic position: Coleoptera, Cerambycidae
Common name: Asian longhorn beetle; Starry sky beetle
More details on the Asian Longhorn Beetle (pdf)

Hosts: A wide range of broad-leaved trees and shrubs, including fruit, forest, ornamental and amenity trees, e.g. apple, citrus, elm, horse chestnut, maple, pear, poplar and willow.

Threats: An exotic wood-borer beetle pest that attacks healthy hardwood trees which has recently become established in areas of the USA. It is a native of SE Asia (China, Korea and Japan) where it is a major problem on broadleaved trees. It has been intercepted at many locations in North America dealing with imported material, and also at several locations in the UK.

Distribution and spread: A major pest in China; Korea and Japan and recent outbreaks have been found in areas of North America, as well as several European countries.

Western Conifer Seed Bug

6. Western Conifer Seed Bug

Scientific name: Leptoglossus occidentalis (Heidemann, 1910)
Taxonomic position: Hemiptera, Coreidae
Common name: Western Conifer Seed Bug or Leaf-footed Bug
More details on the Western Conifer Seed Bug (pdf)

Hosts: Conifers and pines in hedgerows, woodland edges, parks and gardens.

Threats: The western conifer seed bug (WCSB) is regarded as an invasive forestry pest because of the damage it causes during consumption of Douglas-fir (Pseudotsuga sp.) conifer seeds and developing cones of various other species of the pine family (Pinaceae).They also feed on developing seeds and fruits of a wide variety of plants, including dogwood and sumac. Nymph feeding causes significant seed loss in commercially important crops with seed destruction rates of 80% been recorded in some nurseries. Thus, its direct economic impact is a reduction in the quality and viability of conifer seed crops.

Distribution and spread: Previously limited to western North America but in the past 50 years it has increased its range in North America. In 1999 it was introduced into western European countries, by being accidentally transported in timber, and its spread could also possibly have been aided by Christmas tree shipments, where it has spread rapidly and during 2008-2010 influxes of immigrants were reported from the coast of southern England, which have subsequently spread to form a wide distribution throughout the UK but not Ireland.

Emerald Ash Borer

7. Emerald Ash Borer

Scientific name: Agrilus planipennis (Fairmaire, 1888)
Taxonomic position: Coleoptera, Buprestidae
Common name: Emerald Ash Borer
More on the Emerald Ash Borer (pdf)

Hosts: The Emerald Ash Borer (EAB) has been found only in North American species of Fraxinus and there are no data available on the common European species F. excelsior and F. angustifolia, although they are included as ornamental species at risk in North America. In China, the beetle colonises the Asian ash species F. mandshurica (Manchurian ash) and F. chinensis (Chinese ash). Sorbus aucuparia (mountain ash) is not attacked.

Threats: Ash is an important broadleaf tree in the UK, the second most commonly planted genus, and makes up nearly 15% of all broad-leaved woodlands. Its wood is strong with many uses including the manufacture of ladders, flooring, handles, sports goods and furniture. Although there is no evidence to date that the emerald ash borer is present in the UK, the increase in global movement of imported wood, wood packaging and dunnage poses a significant risk of its accidental introduction. In the UK, ash trees can suffer from a variety of root and butt rots that can cause late flushing, thinning foliage and decline leading to eventual death, symptoms similar to those caused by the emerald ash borer. F. excelsior can also suffer from a condition called Ash dieback involving the death of scattered twigs, branches or limbs, especially in the eastern drier parts of the country. Although not fully understood, this may be partially due to root disturbance.

Distribution and spread: An exotic beetle pest that causes significant damage to ash trees (Fraxinus spp.) has recently been introduced into North America. A native of Asia, it is thought that the beetle has been introduced into the country in imported wooden packing material. Ash trees have been widely planted in urban situations in North America and are also economically important as a commercial timber crop. The death of many ash trees, within 2 to 3 years of first showing signs of ill health, is a cause for great concern.


8. Black vine weevil - Otiorhynchus sulcatus (Fabricius, 1775)
9. Cockchafers - Melolontha melolontha (Linnaeus, 1758)
10. Garden chafer - Phyllopertha horticola (Linnaeus, 1758)
11. Oak jewel beetle - Agrilus (Anambus) biguttatus (Fabricius, 1777)
12. Oak Processionary moth – OPM - Thaumetopoea processionea (Linnaeus, 1758)
13. Pine Processionary moth - Thaumetopoea pityocampa (Denis & Schiffermuller, 1775)
Arfogi coed a choedwigoedd Cymru ac Iwerddon i ymladd plâu hen a newydd ag arfau naturiol

Dylunio'r wefan: mach2media a Technoleg Taliesin Cyf.