Invasive Alien Species in Northern Ireland

Dendroctonus micans, Great spruce bark beetle

Dendroctonus micans  (Kugelann)
The great spruce bark beetle is not native to the British Isles and unfortunately, like many potential pests, it can become problematical if introduced outside its natural range. In Europe it feeds mainly on Norway spruce Picea abies but only rarely causes significant damage. Elsewhere in the world it is listed as a potentially serious pest. Unlike the majority (of less harmful) bark beetles it can feed on the cambium of living trees and seriously impair the transport mechanisms within the bark causing slowed growth and, ultimately, death of the tree. Sitka and Norway spruces are both used extensively in commercial forestry in Ireland and are therefore at risk from the accidental introduction of this species.
The adults measure 6-9mm long making this the largest European bark beetle. The body is nevertheless small, black or dark brown and with close-set yellowish hairs. The bark beetles are distinct in having short, downward-pointing heads partly covered by the thorax and therefore concealed, and in having both head and legs retracted out of sight when alarmed or at rest.
They infest the inside of the bark of suitable trees, in the present case spruces of the genus Picea. It is beyond the scope of this article to provide detailing distinguishing features but the photo above, and description given by the USDA Forest Service web site
( should be helpful.
Country of origin
The great spruce bark beetle is a native of the north Palaearctic from northern Europe across Siberia to Japan.
Current distribution
It was first recorded in Britain in 1982 from Ludlow, Shropshire, but has since spread and became common enough to cause economic damage to forestry in Wales and parts of north-west England. Protected Zones were established comprising non-infested parts of Britain and the island of Ireland under EC Council Directive 92/76/EEC. A Control Area was also established around the infected areas west of a north-south line running from Bristol to Morecambe. In the Control Areas a programme of biological control using the predatory beetle Rhizophagus grandis Gyll. was initiated. This seems to have been successful in limiting the success of Dendroctonus and the Control Areas status has been removed recently. The establishment of this species in Britain could have originated in forest products from anywhere in northern Europe or the Eurasian land mass.
Location in Ireland
Not recorded in Ireland other than as an occasional accidental import with forest products.
Life cycle
Mating takes place under bark after the adults hatch from their pupae. The females then emerge from the brood chambers and fly or walk to new sites sometimes on different trees. Here they burrow under the bark to the cambium layer and create extensive egg galleries. The wood frass from the tunnels, mixed with spruce resin, is expelled from the entrance holes and creates ‘resin tubes’ which can be seen and indicate an infestation. In this species the resin tubes are usually a purple-brown colour.
In the cambium the female hollows out an egg chamber in which she lays 100 to 150 eggs. These are covered with frass and sawdust. When the young hatch, these eat further into the tree creating a brood area which enlarges as more larvae hatch. After 6 to 12 months the larvae pupate in the frass and emerge within a few months.
Wildlife and habitat impacts
None known at present; however, the activities of this beetle could potentially provide habitat for a variety of pathogenic fungi and the insects which feed on these.
Human impacts
Reduction in the financial return on investment within commercial forestry.
Key vectors
The main method of spread is with forest products, particularly round timber. It can occur on produce from virtually anywhere in the northern hemisphere where suitable spruce species grow, that is, from British Columbia to New York and from Belgium to Japan.
Once established in an area, attacks on trees spread slowly outwards. The adult beetles fly only at temperatures of 21-23°C. Otherwise spread is by walking which is considerably slower.
What you can do as an individual
Members of the public have a role to play here by reporting suspected occurrences on imported wood or wood products to the Department of Agriculture’s Service Delivery Group, or to AFBI (Agri-food Biosciences Institute, formerly Science Service of DARD, at Newforge Lane), or to CEDaR, Botany Department, Sciences Division, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down BT18 0EU. Tel: 028 9039 5256, email[at]
Advice to specific groups relevant to this species
Apart from the reporting of any suspected occurrences to regulatory authorities, no further action is recommended.
Management measures
Since 1993 the British Isles has been given Protected Zone status, outside the actual infected areas in Wales and NW England, within the European Plant Health Directive.
Further information
For anyone interested in the beetle itself and wishing to know more of its biology and spread:
USDA Forest Service site –
Details of the Plant Health Order as it applies to the UK –
Text written by:
Dr Roy Anderson