Eight- Toothed Spruce bark beetle.

/ by Jon Smith / in Common Pests

Principle species colonised.

Because it loves stressed and dying trees, the eight-toothed spruce bark beetle is most commonly found on fallen trees. The bug will migrate to living Spruce and Pine trees if the population grows.

Identification.

The eight-toothed spruce bark beetle is a cylindrical insect that is about 5 mm long, hairy, glossy, and dark brown when fully grown.

Since it primarily affects spruce, plantations that only have one species planted are especially susceptible to attack. Then, nearby trees, particularly pine, may see substantial increases in insect populations.

Type of symptoms.

Among the symptoms are:

  • browning of living trees’ crowns.
  • The hue of needles lightens, they form mats, and they frequently fall to the ground.
  • The insects create 2-2.5 mm entrance holes on the bark’s surface.
  • On the bark near the base of branches and trunks, feeding larvae make frass, a waste product that resembles sawdust.
  • When woodpeckers attack stems, they rip off the bark to feed on the larvae, causing harm.

The threat to host.

The male beetles begin to fly in search of new host trees in late spring and early summer when temperatures reach 11–16˚C. In order to attract up to four females, the male would bore a nuptial chamber into the wood of a suitable tree and release a scent. To lay her eggs, the first mated female would bore a gallery lengthwise towards the top of the tree. All succeeding females will bore galleries down the tree with niches for each egg. Between thirty and eighty eggs can be produced by them.

When the egg hatches, the damage occurs because the larvae expand and elongate the egg niche and create a pupal chamber where they will pupate beneath the surface of the bark. This causes dieback of the higher branches and, in extreme situations, the entire tree by gravely damaging the channels that carry water and nutrients throughout the tree.

Additionally, the beetle may carry a harmful fungus that can discolour wood and reduce its market value.

Impact / Effect / Significance

In an effort to stop the beetle from spreading to other areas, South East England currently has a delimited zone. Bark from inside the defined area is included in this movement of spruce materials.

The eight-toothed spruce bark beetle is mostly a hazard to spruce trees, but it can also occur on Scots pine or Douglas fir in extremely uncommon and restricted situations.