Hylastes ater (Black pine bark beetle) - Fact Sheet

Identification

Adults are cylindrical and shiny black or slate gray with reddish-brown antennae and elytra.Footnote 1 Footnote 2 Adults are 3.5 to 5.0 mm long and 1.4 mm wide.Footnote 1 Footnote 2 Newly emerged beetles are uniformly reddish-brown but darken as they mature.Footnote 2 When viewed from above, a small portion of the head projects beyond the pronotum.Footnote 2 The head is directed downwards and is prolonged into a short snout.Footnote 2

Host Trees

Pinus (main host), Araucaria, Abies, Larix,Picea, Pseudotsuga and Thuja.Footnote 1 Footnote 2

Location Of Infestation Within The Tree

This species breeds primarily in the inner bark of roots, fresh stumps, the base of dead and dying trees or logs in contact with the ground.Footnote 1 However, immature beetles feed on the inner bark of pine, spruce, true firs, Douglas-fir and larch seedlings.Footnote 1

Host Condition

Breeding occurs in fresh stumps, recently dead or broken host material and dying trees.Footnote 1

Distribution

Europe.Footnote 1 Introduced into Chile, Japan, South Africa, Australia and New Zealand.Footnote 1 Footnote 2

Signs and Symptoms

Immature beetles remove patches of bark and inner bark from seedlings at ground level.Footnote 1 This feeding can cause heavy mortality.Footnote 1 Seedlings that survive attack will show resin-encrusted wounds in the major roots and on the portion of the stem below ground.Footnote 2 Injured seedlings first appear wilted and sickly, then often turn bright red, with needles becoming hard and brittle.Footnote 1 Injured seedlings tend to appear in clumps near infested stumps or logs, but may also be found at considerable distances from breeding sites.Footnote 1 In addition to the damage caused by feeding, beetles can also vector several black stain root diseases.Footnote 1

Adults prefer moist breeding habitats especially underground roots and the underside of logs that are in contact with the ground.Footnote 1 A reddish, sawdust-like frass is expelled from entrance holes when adults bore into the bark. Brood galleries consist of a short entrance tunnel leading to an oblique nuptial chamber.Footnote 1 From this chamber the female bores a uniramous gallery (8 to 13 cm long) that is packed with frass and is usually parallel with the grain of the wood.Footnote 1 However, any males that are present will clear debris from the central egg gallery.Footnote 1 Egg galleries reach but do not engrave the surface of the sapwood, except in small diameter material.Footnote 1 Footnote 2

About 100 eggs are laid in individual niches along the walls of the egg gallery.Footnote 2 Larval galleries initially occur at right angles to the egg gallery, but eventually become random and ultimately obliterate both the early larval galleries and those made by the parents.Footnote 1 Footnote 2 Upon maturation of the brood, groups of about 40 (up to 120) beetles may be present in broad irregularly shaped communal galleries underneath the bark.Footnote 2

Adult Hylastes ater (3.5-5.0 millimetres long)
A - Adult H. ater (3.5-5.0 mm long).
Maturation feeding by Hylastes ater on seedlings. Note reddish foliage
B - Maturation feeding by H. ater on seedlings. Note reddish foliage.
Black staining of root collar associated with Hylastes ater attack
C - Black staining of root collar associated with H. ater attack.
Hylastes ter egg galleries (8-13 centimetre long). Note frass packed vertical gallery
D - H. ater egg galleries (8-13 cm long). Note frass packed vertical gallery.
Resin-encrusted wound caused by immature Hylastes ater beetles
E - Resin-encrusted wound caused by immature H. ater beetles.
Immature beetles within communal galleries under the bark
F - Immature beetles within communal galleries under the bark.
Immature beetles feeding on the inner bark of a seedling
G - Immature beetles feeding on the inner bark of a seedling.

Photo credits

  • A Daniel Adam, Office National des Forêts, France, Image 2515012, www.invasive.org, Feb. 23, 2004
  • B William M. Ciesla, Forest Health Management International, Image 1428130, www.invasive.org, Nov. 19, 2003
  • C William M. Ciesla, Forest Health Management International, Image 1428133, www.invasive.org, Feb. 23, 2004
  • D Forest Research, New Zealand
  • E Forest Research, New Zealand
  • F Forest Research, New Zealand
  • G Forest Research, New Zealand
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