Sélection - European Institute of Planted Forest

Pine shoot beetle

Tomicus piniperda (L.) (Coleoptera, Scolytidae)
Synonyms: Blastophagus piniperda, Dermestes piniperda, Myelophilus piniperda.

Pine (Pinus), fir (Abies), spruce (Picea) and larch (Larix) species.

Tree top discoloured and rarefied.
Yellow discoloration and curving of shoots as a result of adult beetles feeding inside the shoots (between April and February. Presence of pitch tubes on the shoots with resin nuts. In the shoot axis presence of a feeding gallery, sometimes with the beetle still inside. Affected shoots can fall and be found lying on the ground (Photo 1).
Presence of pitch tubes and sawdust around bark holes on the trunk (Photo 2).
Presence of galleries under the bark (one longitudinal gallery (2-2,5 mm wide and 8-12 cm long) and several larval side galleries (Photo 3).
In the gallery system eggs, larvae, pupae and (immature) adults can be present (Photo 4).
Adult beetles are black or bicoloured (reddish elytra and black pronotum) and 3-5 mm long.

Breeding of beetles is often fatal for weakened trees.
At high population levels massive attacks can lead to the death of healthy trees.
Beetles transmit bleu-stain fungi.
Growth reduction when many shoots are tunnelled by adult beetles. Shoot damage also reduces value of Christmas trees.

There is one generation per year. Females lay eggs during several, consecutive periods giving rise to up to four ‘sister generations’.
In warm regions, adults fly all over the year when temperatures are above 9°C; in temperate and cold regions they overwinter in galleries at the base of trunks (with thick bark) in northern Europe and in shoots elsewhere. Adults disperse in late winter - early sprring It is possible to see two annual flying peaks (one in spring and one in autumn). In southern Europe, two similar species co-occur (Tomicus piniperda and T. destruens).
The female bores a vertical gallery under the bark and lays eggs along the gallery. Larvae feed on the phloem during at least 55 days.
Normally only weakened trees, logs and fresh stumps are used as breeding sites. During population outbreaks also healthy trees are attacked.
New adults emerge in April - June and search for shoots for their sexual maturation. They make a gallery in the shoot axis. The sexual maturation period is long and can go on until October/November.
The species overwinters as larva or adult at the base of trunks (with thick bark), in stumps or in shoots.

Weakened trees are more susceptible to beetles attacks. Therefore, attacks are more intense in successive years of drought, on trees ravaged by fire or on fallen trees.
Timber piling in or near stands increases the risk of tree attacks.

Very wide geographical distribution, extending from Portugal to Japan, and from northern Fennoscandia to North Africa. It has been accidentally introduced in North America.

Where allowed, registered insecticides can be applied on infested piles to prevent attacks in neighbouring stands.

Outbreaks are likely to increase in most of Europe because increased summer droughts, storms and fires will provide more favourable conditions for this secondary bark beetle.
In contrast to most other bark beetles in Europe, T. piniperda already occurs at outbreak densities throughout the continent. Thus, range shifts are not expected to occur.