Tomicus piniperda (Pine Shoot Beetle) - Fact Sheet

Description of the adults

Adults are 3 to 5 mm longFootnote 1 and shaped like little barrels. Their head and chest are shiny black and their wing covers are reddish-brown to black. Their heads are visible from above, not hidden under the hard plates of their backs. The wing covers, as in very many beetles, are marked with rows of bumps crowned with hairs. These rows are separated by spaces, giving a striped appearance to the wing covers. In this beetle and many related beetles, the wing covers slope steeply downward toward the rear (to form the elytral declivity). Distinctive for this species is that, within this declivity, the second space from the midline on either wing cover is noticeably broad and hairless. Also distinctive is that the antenna has 6 segments between the long base and the clubbed endFootnote 1. Both of these features can only be seen with the help of a good microscope.

Host Trees

Pines (genus Pinus) are the main hosts for the beetle. Most species are attacked, but only the non-native Scotch pine (Pinus sylvestris) seems to suffer badly. Other conifers (for example spruce, larch, fir, Douglas-fir) have also been attacked, but the beetle does not prefer them and only attacks them when little else is leftFootnote 1, Footnote 2. The beetle prefers larger standing trees in which to lay eggs (at least 12 cm in diameter). Trees of all ages can be attacked, but dying, stressed (by drought, needle loss, fire or snow damage, etc.) as well as recently-cut stumps, felled and wind-thrown trees are preferred. Healthy trees may also be attacked when beetle populations are high, but these attacks have high failure ratesFootnote 3.

Parts of the tree that become infested

Larvae feed on the inner bark along the trunk from the root collar to the lower or middle crown. Immature adult beetles tunnel into young shoots to feed, where they may also pass the winter. Mature adults may pass the winter in short tunnels at the base of host treesFootnote 1. Shoots in the top third of the tree are the ones usually attacked by the immature adultsFootnote 1. In late October to November the adult beetles go to the base of the trunk where they bore into the bark or into the soil to pass the winter. In warmer climates they may pass the winter inside the shoots.

Signs and symptoms

Openings to the egg-laying tunnels can be identified by the presence of fine reddish-brown frass on the bark surface of trees. If energetic and healthy trees are attacked, whitish pitch tubes can also be seen around the entrance holes.

If you peel back the bark, the feeding and egg-laying tunnels will be visible. Females chew single, simple egg-laying tunnels, oriented up and down from a central entrance hole. These egg galleries are within the inner bark and are 10 to 25 cm long and about 2 mm wide. Females lay single eggs in individual egg niches on both sides of the egg gallery. After hatching, larvae chew their own feeding galleries, 2.5 to 10 cm longFootnote 1, that run more or less at right angles to the egg gallery before curving away.

Cut wood or exposed wood might show blue colouration because adult beetles can carry blue stain fungi, which stain the sapwood.

Once they have pupated and become adults, but before they have completely hardened, the immature beetles bore round exit holes about 2 mm in diameter at the end of their feeding tunnels. The immature beetles then fly to the crowns of host trees and tunnel into the current year's shoots to feed. This stage is necessary before they can become mature. They tunnel to the centre and hollow out 2 to 10 cm of the shoot. Shoot feeding does not kill the tree but can cause reductions in height and diameter if many shoots are damaged. Damaged shoots display a round entrance hole (2 mm diameter), usually surrounded by pitch, and one to a few galleries. Damaged shoots turn yellow then red, droop, become dry and easily broken, and eventually break off near the entrance hole. After windstorms, the broken-off shoots give the tree the appearance that it has been pruned. The shoots may lie all about the forest floorFootnote 1.

Where it is found

The pine shoot beetle is naturally found from Asia through Europe and northern Africa. It has been introduced into eastern North America. In Canada, the last surveys found it still expanding its range in both Quebec and Ontario, and it is found south of a line from approximately Sault Ste. Marie in Ontario, straight across Quebec to the New Brunswick border. It has recently been found in New Brunswick.

Adult Tomicus piniperda (3-5 millimetres long) tunnelling in a shoot.

A - Adult T. piniperda (3-5 mm long) tunnelling in a shoot.

Tomicus piniperda egg (10-25 centimetres long) and larval (4-9 cm long) galleries. Note vertical orientation of egg galleries.

B - T. piniperda egg (10-25 cm long) and larval (4-9 cm long) galleries. Note vertical orientation of egg galleries.

Pitch tube surrounding entrance hole on brood tree.

C - Pitch tube surrounding entrance hole on brood tree.

Round entrance hole (2 millimetres wide) on infested shoot.

D - Round entrance hole (2 mm wide) on infested shoot.

Green flagging on shoot caused by maturation feeding.

E - Green flagging on shoot caused by maturation feeding.

Frass expelled from Tomicus piniperda entrance holes.

F - Frass expelled from T. piniperda entrance holes.

Red flagging caused by maturation feeding within current year's shoot.

G - Red flagging caused by maturation feeding within current year's shoot.

 

Photo credits

  • A Gyorgy Csoka, Hungary Forest Research Institute, Image 1231204, www.invasive.org, April 4, 2004
  • B William M. Ciesla, Forest Health Management International, Image 0017008, www.invasive.org, March 14, 2004
  • C Stanislaw Kinelski, Image 1258125, www.forestryimages.org, May 22, 2004
  • D Gyorgy Csoka, Hungary Forest Research Institute, Image 1231203, www.invasive.org, April 6, 2004
  • E Bruce Smith, USDA APHIS PPQ, Image 0805094, www.invasive.org, April 5, 2004
  • F Stanislaw Kinelski, Image 1258126, www.forestryimages.org, May 22, 2004
  • G Robert A. Haack, USDA Forest Service, Image 3225083, www.invasive.org, April 4, 2004
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