Public Enemy No.1 for the Spruce Tree
Trees of the UK are under threat from a variety of diseases and pests that do serious damage and can even kill the tree. One such pest is the great spruce bark beetle (Dendroctonus micans) which is found in forests and woodland right throughout mainland Europe. It targets spruce trees, as the name suggests by laying eggs under the bark. The growing larvae eat the inner bark layers, weakening and often killing the tree.
As with some other pests, the beetle was accidentally introduced to the country in 1982, most likely in a shipping of timber from abroad. It established itself in the west of England and Wales, extending eventually to the south of Scotland.
The damage caused by the beetle varies and if caught in time, the tree can be saved if the wood can be salvaged before the tree dies. The tree will die if there has been several years of continual attack, where big populations inhabit the are under the bark. The beetles are likely to move onto nearby trees once the tree has been killed. No spruce variety is safe, as the beetle will breed in all species found in the UK.
Signs of a spruce bark beetle attack include browning foliage covering some or all of the crown of the tree and small groups of trees dying in close the female beetle burrowing into the bark to lay her eggs. These tubes might be white, cream, brown or even purple in colour. Resin bleeds and loose bark are further signs of spruce bark beetle.
Gently remove the bark and look for beetle activity. You will see insect faeces and bark that’s been compacted into islands. You might see adult beetles and larvae under the bark. For any suspected disease or pest activity in your trees, contact Dorset Tree Surgeon like Dorset Tree Surgeon https://kieranboylandtreeservices.com/
Beetles live for a long time for insects, between 12 and 18 months. This long, life cycle means that generations overlap, so it’s common to find both adults and larvae together at any time of the year. The adults are around 8mm long and 3mm wide, black in colour with orange hairs. Females can produce around 300 eggs in groups found in inter-connecting chambers.
The larval stage consists of five different growth periods, with the beetle becoming progressively larger each time. When the fully-grown beetles emerge, they are light brown in colour, but their colour develops into a darker brown or black shade as they mature. They mostly walk, but as temperatures rise during summer months, they are also known to fly.