If the spruce needles are yellowing, this could be due to the Sitka spruce aphid. A simple test will tell you if it's infested. Then act quickly.
Anyone who has a spruce tree in their garden should check from time to time whether it is infested with harmful lice. There is a louse that can damage some types of spruce so severely that they die. We're talking about the Sitka spruce aphid. This is a pest that mainly eats older needles near the trunk. These then turn yellow first, but a short time later they turn brown and fall off. Then at the latest you should become active. It is even better if you regularly check the tree for aphid infestation. This is particularly advisable after mild winters, because then adult animals can easily survive.
What does the Sitka spruce aphid look like?
The Sitka spruce aphid is related to the aphids and accordingly looks very similar to them. It is about 2 millimeters in size and green. She also has rust red eyes. It usually occurs in large populations, as it can multiply rapidly even in mild winters. It is also active all year round. She pricks the cells with her proboscis and sucks them out, causing the needles to discolor and fall off. This type of damage occurs mainly in spring.
You can easily check whether your trees are infested with the Sitka spruce aphid. There's a simple trick to spotting an infestation.
How to test if your spruce has lice:
Take a piece of paper and a stick and tap on the branches with them. You have to hold the paper underneath. The 2 millimeter lice fall onto the piece of paper on which you can then see them with the naked eye. If more than five of these lice land on the paper with the tapping action, then you should take action.
How to get rid of the Sitka spruce aphid
Set up insect hotel:
Control of the Sitka spruce aphid is particularly important in spring and winter, when the aphid's natural enemies are not active. These include beneficial insects such as lacewings and ladybugs. Offer these beneficial insects a nesting place or aWinter quarters, then you can fight the Sitka spruce aphid faster. Simply set up an insect hotel in your garden.
Use preparations that are gentle on beneficial organisms:
Otherwise it is advisable to use preparations based on rapeseed oil or potash soap. They protect beneficial insects and are still very effective. For example, we can recommend Celaflor Naturen pest-free (available here). This is a spray based on rapeseed oil. Prepare the spray according to the manufacturer's instructions and spray the branches and trunk thoroughly with it. Two sprays two weeks apart is usually enough to get rid of the Sitka spruce aphid.
Avoid waterlogging and dryness:
Sitka spruce aphids primarily infest coniferous trees that suffer from waterlogging or soil that is too dry. Therefore, always make sure that the soil is evenly moist and loose.