The walnut tree is one of the most robust tree species. However, he is not completely spared from illness. One of the most common problems with walnuts is fungal infestation. Our guide explains how you can recognize one and how you can take action against it.
How do you recognize and combat fungal infestation on walnut trees?
A walnut tree with fungal infection shows symptoms such as brown or grayish-brown leaf discoloration, curled or stunted leaves and increased leaf drop. To combat fungal infestation, biological fungicides should be used that are environmentally friendly and do not affect the harvest.
Countless types of mushrooms possible
Unfortunately, there are numerous species of fungi that settle in gardens year after year and some also nest on walnut trees. Some cause severe, life-threatening damage, others can be combated relatively easily.
Important: You should IN ANY CASE react immediately if you notice a fungal infection on your walnut tree. In most cases, it is not possible to accurately identify the fungus in question (the most you could do is consult an expert).
Note: The most important fungus associated with the walnut is Diplocarpon mali, which causes Marssonina disease.
Symptoms of fungal infestation
Walnut trees usually show the following symptoms when infected with fungus:
- brown and/or greyish-brown leaf discoloration
- curled and/or stunted leaves
- Leaves dry out and increasingly fall off
- new shoots remain out/grow very thinly
- thin green branches hang down weakly
- Fruits fail/do not develop properly
- Tree is thinning out more and more
- Smear on the leaves and/or green branches
Fight fungal infection in walnuts
Fungicides (€8.00 on Amazon) that are specifically made for fungal treatment on fruit trees usually work the fastest and best. We advise you to only use organic products. These even ensure that you can harvest and enjoy any fruit in the fall despite the treatment. In addition, organic fungicides are environmentally friendly.
Note: If you decide to use chemical products, you must expect that the walnuts will be contaminated with pollutants afterwards. Then it is better NOT to eat the nuts. Incidentally, chemical fungicides are also toxic to insects. This is another reason why it is not recommended to use such products.
Extra: tree fungus infestation
The fungal infections defined above refer to fungal species that trigger an optically small fungal spore infestation. In addition, there is also tree fungal infestation - this is observed much more often: easily recognizable fungal sponges form, very often on the tree trunk.
There are two things to consider:
- Tree mushrooms are not always edible (although they may look inviting).
- Tree fungi are not necessarily harmful to walnut trees.
Despite the second point, you should act:
- Remove tree fungus to prevent spread.
- Score the bark/wood with a sharp knife.
- Green fabric available? Fighting can still work!
- Inner fabric dried out/shimmering yellowish-green? Fungus has penetrated the interior of the walnut and conventional measures no longer make sense.
- In the latter case, consult experts from the plant protection office.