Walnut Tree: Detect and combat diseases and pests

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Hardly any plant can be permanently protected against diseases and pests, not even the walnut tree. Although he is quite robust, but it can put a lot of pathogens.

Walnut Tree: Detect and combat diseases and pests

Many trees and plants have a natural protection against pests. So also the walnut tree. While human noses find the smell of the tree pleasant, it repels pests relatively reliably. But even the best natural protection does not say that your walnut can not get sick.

What you can tell about diseases or pests and what you can do about them is explained in this article.

Common pests in the walnut tree

Some pests are not deterred by the smell of the walnut tree. Gall mites, lice and aphids, but also caterpillars can be partially settled in the tree. Another troublemaker is the walnut fruit fly, which lives up to its name.


Aphids, which are among the sucking pests, you will find increasingly on the leaf underside. As a rule, you do not have to act immediately if you discover the lice. Only in case of heavy infestation and the rolling up of many leaves, you should take the following measures:

  • Remove the affected shoots
  • In case of lower infestation: Spray the lice directly with a lye. Alternatively, you can use natural pesticides made from potash soap, pyretrum and rapeseed oil.
  • If the infestation is strong, chemical agents are recommended - but beware: the walnuts are no longer suitable for consumption.

A good way not only to prevent lice infestation, but to prevent, is the use of natural predators of aphids. Settle parasitic wasps, ladybugs or lacewings in your garden. Although the insects need a suitable environment for their species, they not only protect your walnut tree, but also many other plants in the garden.

Leaf feeding on the walnut:

Butterfly caterpillars, blue screen and willow drill caterpillars partly settle on walnut trees. Again, you first try to control the caterpillars organically. If the tree has not grown up yet, you can collect the caterpillars with your hands.


Bluesiebraupen are pests that can damage the walnut tree massively. The insects eat their way through the bark, leaving passages in the trunks and branches. They recognize the blue caterpillars by their yellowish-white body, which is covered by point warts. The caterpillar can grow up to six inches long. To fight them, the following way is recommended:

  • Remove all affected shoots
  • If the caterpillar has already settled in the trunk, the tree should be felled.

Walnut fruit fly:

Another pest that attacks the tree is the walnut fruit fly. They recognize the pest primarily from the damage it leaves behind: black spots on the still green shells of the fruit. The maggots of the fruit fly penetrate into the pericarp and eat it up slowly, whereby it becomes soft and moist. Tips to combat: Collect all affected fruits and destroy them.

Prevention is of course more useful. Yellow sheets, such as These here, just hang up in different places in the tree and keep accordingly the walnut fly away. An alternative, however, is more complicated, is tensing the tree with a fly net.

Diseases of the walnut tree

Which disease hides behind a symptom is not always easy to recognize. Therefore, we recommend in advance, in case of doubt, to consult a specialist and take targeted action.

Cherry leaf roll virus

The cherry-roll virus is one of the diseases of a walnut tree that can not be fought. The virus causes spots that appear on both the fruit and the leaves and develop a pattern of lines.


Powdery mildew forms bright surfaces on the leaf underlays, which have a floury touch. Remove the shoots carefully and carry out a pesticide-control. Look for funds based on night sulfur or organic matter. Apply the product once a year if possible before flowering.

Fungal infections:

Brown and greyish brown leaves indicate mushrooms. If you lift the leaves, you may see some fruiting bodies on the underside. Especially in humid summers the diseases occur frequently. As part of the fight again remove the affected parts of plants. Special pesticides do not exist in this case.


If growths on shoots form, it is often a case of bacterial infection.To prevent the bacteria from penetrating you should regularly inspect the walnut tree for damage and keep it clean. Even after cutting the tree, bacterial infection can occur at the interfaces. Dry the cut edge carefully.

Video Board: The Black Walnut: Trees, Pests & People.

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