Suspected findings of Enaphalodes rufulus (red oak borer) on wood imports: addition to the EPPO Alert List
Plant Health Inspectors in the United Kingdom intercepted consignments of sawn oak wood (Quercus spp.) which showed symptoms of live wood borer activity with small amounts of fresh frass observed beneath bore holes in the wood. Although it was not possible to recover and identify specimens, there were strong indications that the activity observed was caused by larvae of Enaphalodes rufulus (Coleoptera: Cerambycidae, red oak borer). Because E. rufulus is a serious pest of oaks and is probably able to establish in the UK, the affected consignments were intercepted and refused entry. Although the EPPO Secretariat has not been informed of any other interception of this pest in Europe, E. rufulus is an economically important wood-boring species in North America (its area of origin) and the recent UK interception suggests that it might have a pathway to enter Europe (e.g. sawn wood from North America), thus it was decided to add it the EPPO Alert List.
Enaphalodes rufulus (Coleoptera: Cerambycidae) – red oak borer
Why: In 2008, the UK NPPO intercepted consignments of sawn oak wood showing signs of infestation by wood borers. Observations strongly suggested that the wood was infested by Enaphalodes rufulus. Although the identity of the pest could not be ascertained, this finding suggested that E. rufulus, which is an economically important wood-boring insect of red oaks in North America, could enter the EPPO region via imports of oak wood.
Where: E. rufulus is native to North America, it occurs in the southeastern part of Canada and the eastern part of the USA.
EPPO region: absent.
North America: Canada (Ontario, Quebec), USA (Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Vermont, Virginia, Wisconsin).
On which plants: most oak species (Quercus spp.) in eastern North America can be attacked by E. rufulus. Its preferred hosts belong to the red oak group (Erythrobalanus): Quercus rubra (northern red oak), Q. velutina (black oak), Q. coccinea (scarlet oak). Other oak species are less commonly attacked: Q. alba (white oak), Q. stellata (post oak), Q. palustris (pin oak), Q. macrocarpa (bur oak), Q. lyrata (overcup oak), Q. laurifolia (laurel oak). There is no data on the susceptibility of European oak species (e.g. Q. petraea, Q. pubescens, Q. robur).
Damage: damage is caused by larvae which bore tunnels inside the wood of their host trees. Galleries created may then become infected with decay fungi. Damage of E. rufulus to oak wood can be economically important. In the 1980s, in the USA, it was estimated that 38% of oak wood used for lumber, cooperage and veneer was affected by E. rufulus, and could lead to 40% reduction of the tree value at the time of sawing. Normally tree mortality is not associated with E. rufulus infestations but in the early 2000s, severe mortality of red oaks (Q. rubra, Q. falcata and Q. velutina) was observed in the Ozark National Forest (Arkansas) and then in the nearby states of Oklahoma and Missouri. This severe oak mortality and decline which affected tens of thousands of oaks, primarily Q. rubra, was associated with an unprecedented outbreak of E. rufulus. Although there might be other factors involved (e.g. drought), E. rufulus was considered to be an important component of this severe oak tree decline.
E. rufulus has a 2-year synchronous life cycle. Adults are nocturnal and can be found from mid-June to mid-August. Mating takes place on the host tree and the females lay an average of 110 eggs, mainly in bark crevices, under lichen patches and climbing vines. Young larvae bore directly through the bark and spend their first year in the phloem making small tunnels. The 2-year-old larvae make larger tunnels and bore into the xylem where pupation takes place. The adult emerges near the original oviposition site by gnawing an oval hole through the bark.
Pictures can be viewed on the Internet: http://www.invasive.org/browse/subthumb.cfm?sub=374&start=1
Dissemination: adults can fly but data is lacking on their potential for natural spread. Over long distances, trade of wood and wood products can disseminate E. rufulus (imports of Quercus plants for planting from non-European countries are usually prohibited).
Pathway: Quercus wood and wood products from Canada and USA.
Possible risks: because larvae are hidden in the wood, they may be difficult to detect during inspection. The UK interception, although not confirmed, suggests that pathways of introduction into Europe exist (e.g. sawn wood). Considering its geographical distribution in North America, it is likely that E. rufulus can establish under the climatic conditions of Europe. In forests, control measures are limited (removal of highly infested trees, general measures to encourage tree vigour); in parks and gardens, insecticide treatments can be applied for high value trees. One of the main uncertainties is the availability of host plants in the EPPO region. Red oaks are grown for ornamental purposes and apparently Q. rubra is increasingly planted in forests (because of the quality of its wood) but data is lacking on its current distribution in European forests and economic importance. In addition, data is lacking on the susceptibility of European oak species to E. rufulus. Nevertheless, it cannot be excluded that oak wood boring pests such as E. rufulus may present a risk to European forests, timber industry, nurseries and amenity trees planted in parks and gardens.
EPPO RS 2008/178
Panel review date - Entry date 2008-09
Sources
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