There are primarily 2 pest species that target your blue spruce. You can find out what these are and how to identify the pests here. There are also useful tips for effective combat.
What pests attack blue spruce trees and how do you fight them?
The main pests of a blue spruce are the book printer (Ips typographus), a bark beetle, and the spruce gall louse (Sacchiphantes viridis). Prevention and control include judicious care, pheromone-containing sticky traps, removal of infected branches, and use of paraffin oil insecticides.
Infestation with book printers threatens total failure
They are 4-5 mm long, have a brown body and nest in droves under the bark. The bark beetle species of the book printer (Ips typographus) has specialized in infesting spruce trees in order to multiply explosively there. Under high infestation pressure, up to 25,000 beetles nest in your blue spruce, so that the tree is hopelessly lost.
Since there is currently a lack of effective control agents, the only way to keep the small invaders away from your Norway spruce is through careful care. In a he althy tree, the sap flows so abundantly that the pests drown in it. Therefore, water regularly without causing waterlogging. Avoid nitrogen-rich fertilization and injuries to roots and bark. Pheromone sticky traps capture approaching book printers in the early infestation stage.
How to recognize a spruce gall louse infestation
If your blue spruce is covered in small, pineapple-like galls in spring, the spruce gall louse (Sacchiphantes viridis) is doing its disastrous work. The next generation of lice grows in the galls and sucks the juice out of the leaves. Under high infestation pressure, the needles turn brown or the entire shoot dies. This is how you take action against the pests:
- Cut out and destroy affected branches
- Treat the blue spruce with an insecticide based on paraffin oil
- Check the pH value in the soil and adjust it to 6.5 to 7.5 if necessary
Mulch regularly with wilted lawn clippings to keep the spruce gall louse at bay. One of the most effective methods of prevention is having a rich population of beneficial insects in the garden. Lacewings, parasitic wasps, ladybirds and all kinds of birds enthusiastically hunt the parasites.
Tip
If you plant a blue spruce in your garden, please avoid the immediate vicinity of rhododendrons when choosing a location. In summer, the pathogens of the fungal disease spruce needle rust (Chrysomyxa) live on the flowering trees and tend to switch hosts to your spruce and can cause significant needle drop there.
