Bark beetles are among the most dangerous pests for spruce trees. They primarily attack weakened trees. In this article we will explain to you how you can recognize that this unpleasant insect has settled on your conifer and what to do if it is infested.
How do you recognize bark beetles on spruce trees?
A bark beetle infestation on the spruce can be recognized by accumulations of drill dust, circular drill holes, fresh resin discharge, yellowed needles on the tree, green needles on the ground and fallen pieces of bark. An infected spruce usually cannot be saved and must be removed.
How do you recognize a bark beetle infestation on the spruce?
Depending on the stage of infestation, the settlement of bark beetles can be recognized by various characteristics:
Infestation stage 1 – Bark beetles bore into the trunk:
- Drill dust accumulations on the bark, at the base of the trunk and in the surrounding vegetation
- circular drill holes with a diameter of approx. 3 mm in the bark
Infestation stage 2 – Bark beetles lay their brood (approx. 2-3 weeks after drilling):
- fresh resin flow
- yellowed needles on the tree
- green needles on the ground
- “Woodpecker mirror” (traces of woodpecker activity on the trunk)
Infestation stage 3 - Bark beetles have left the now dead spruce:
- green crown
- fallen bark pieces
How do bark beetles behave on the infected spruce?
Bark beetlesbore through the bark, in the juicy part of which they develop. By feeding, the adult beetles and larvae destroy the bast tissue that is vital for the spruce.
The bark beetle species book printers and engravers are particularly dangerous for conifers:
- TheBook printer attacks older trees and thicker trunks.
- Thecopper engraver prefers thinner trunks and stronger branches.
Problem: Sometimes bark beetles “only” colonize the crown areas of older spruce trees - then the infestation is difficult to detect.
Can you combat bark beetle infestation on spruce trees?
Once a spruce tree is infected, it is difficult to saveThe use of insecticides is prohibited on standing trees and does not work. It is rarely enough to saw off affected branches - the spruce usually has to be felled completely. This should be done as quickly as possible in compliance with local guidelines.
To speed things up, remove the bark from the affected tree andburn the bark and larvaeAlthough this doesn't save the directly affected spruce, it does protect neighboring trees. The basic rule is:Dispose of infected tree parts quickly and thoroughly
Tip
Specifically preventing a bark beetle infestation on the spruce
Bark beetles can fly over distances of up to 600 meters. Therefore, not only spruce trees in the forest, but also those in parks and private gardens are at risk. The pests mainly attack weakened trees. Therefore, the only chance to prevent a bark beetle infestation is to keep your own spruce tree vital and he althy. Pay attention to proper care with a good supply of water and nutrients.
