Present in United Kingdom
Notifiable – No
Scientific name – Hylobius abietis (H. abietis)
The large pine weevil (above), also known as the large brown pine weevil, is a destructive pest of young conifer trees. It is especially destructive of pine (trees in the Pinus genus) and spruce (Picea genus) seedlings planted on commercial forest sites where earlier crops of conifer trees have been harvested during the previous five years. However, it can similarly attack other replanted species of trees, including broadleaved species.
Large pine weevil is found in all parts of the United Kingdom, across most of northern Europe and Asia as far south as Armenia, Turkey and Kazakhstan, and as far east as China and Japan. It has been recorded in New Zealand, but is no longer believed to be present there.
Although the large pine weevil can attack many species of conifer and broadleaved tree, the species most at risk in the UK are commercial conifer species grown for the softwood timber trade. See 'The threat' below for an explanation of why this is the case.
The two main conifer species grown in commercial forestry in the UK and at risk are our native Scots pine (Pinus sylvestris) and the introduced Sitka spruce (Picea sitchensis). Also grown and at risk are Douglas fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla) and Norway spruce (Picea abies). Although Corsican pine (Pinus nigrus) and lodgepole pine (Pinus contorta) are also grown in the UK, they now tend to be replaced after harvesting by other species more resistant to pests and diseases.
Large pine weevil could cause significant damage to our commercial conifer forests and associated industries if it were left unmanaged.
Although adult weevils can attack a range of conifer and broad-leaved species, the pest only lays its eggs on or near to the bark of the stumps and roots of recently felled or dead conifer trees. The life cycle may last between one and three years in the UK, depending on the local temperature. It passes through the egg, larval and pupal stages in the root stumps before the adult weevils emerge. They then move away to feed on the bark of nearby living trees and other woody plants.
Adult weevils have a preference for feeding on young trees, including seedlings only a few centimetres tall, when the plants are most vulnerable. Their feeding damage can kill young trees if it girdles their stems: a single weevil can damage or kill several young trees, so a large population of weevils could kill thousands of planted seedlings.
Thousands of conifer root stumps and young, replanted seedlings can be present together on a recently harvested site, so that if protective measures are not taken, the young trees can be at serious risk from emerging weevils. Left unmanaged, pine weevils often destroy an average of 50 per cent of young trees on a restocked (replanted) conifer site, and in worst-case scenarios they can destroy all of them.
Adult weevils can travel up to two kilometres in a few days during warm weather suitable for flight. Therefore if the immediate site has no young trees on it, nearby recently restocked sites, and any other young trees in the vicinity, can be at risk.
Hundreds of millions of pounds worth of investment and thousands of jobs in the nursery, forestry, timber haulage and timber-processing industries depend on the UK’s conifer forests and their good health. It is therefore essential that forest and woodland managers remain constantly alert for this pest, and take appropriate and timely action to mitigate the risks which it poses. See 'Management and control' and 'Related materials' below for links to advice and guidance for forest managers.
Identification and symptoms
Adult weevils are about 10 to 13mm long (not including the elongated ‘snout’ or rostrum), and are dark brown with patches of yellow or light brown hairs arranged in irregular rows on the abdomen/wing cases. The legs are black or deep red with a distinctive tooth on the femora (the segment of the leg nearest to the body) and at the end of the tibiae (lower leg).
They can be seen all year around, but usually hibernate in the winter.
Fully grown larvae (above) are cream-coloured and soft bodied, with a hardened brown head. They reach 14 to 16mm in length, are curved in shape, and legless.
Adult presence is typically recognised by feeding damage to the bark of live young trees, appearing especially between April and September. This damage takes the form of patches of removed bark (known as feeding scars), which can lead to deformed or killed seedlings.
Report a sighting
British foresters are trained to be alert for large pine weevil, and how to control it, so we do not require reports of suspected sightings from members of the public.
Management and control
Effective control can be achieved by the use of one of the following methods, or more than one of them in combination: applying insecticides, debarking stumps, removing stumps, biological control using natural predators, restocking sites with weevil-resistant plants, timing felling and replanting to avoid peaks of weevil activity, letting harvested sites lie fallow for a period before restocking them, and using natural regeneration instead of replanting to restock sites. (Naturally regenerating sites are less susceptible to large pine weevil damage than planted sites.)
However, not all of these methods can be deployed on all sites. Factors such as cost, terrain, accessibility and site suitability will influence decisions about which ones are practicable, and in what combination.
See 'Related materials' below for our advice and guidance for forest managers on recommended methods of control
Forest Research has led work to develop non-chemical and reduced-chemical means of dealing with large pine weevil. One outcome has been the on-line Hylobius management support system (MSS), which forest managers can use to work out a cost-effective, integrated management strategy tailored to their circumstances. It resembles similar systems used in agriculture, and users can access it with an annual subscription. See ‘Related materials’ below.
- Interim guidance on the integrated management of Hylobius abietis in UK forestry
- Hylobius management support system (MSS)
- The assessment of site characteristics as part of a management strategy to reduce damage by Hylobius
- Managing the threat to restocking posed by large pine weevil: the importance of time of felling of spruce stands
- Integrated forest management of Hylobius abietis
- Managing the pine weevil on lowland pine
- Developments in the integrated management of pine weevil
- The effect of temperature on development and life cycle of the pine weevil (Hylobius abietis) and the potential impacts of climate change
- The influence of a changing climate on development and life cycle in the pine weevil, Hylobius abietis
- The influence of climate change on forest insect pests in Britain