Overview of the most common walnut tree diseases
- Fungi and bacteria as well
- Insects (including larvae)
- Marssonina disease in the walnut tree - causes, symptoms, control
- Fungal attack on the walnut tree - symptoms and treatment
- Special features of the walnut tree - this is what distinguishes the plant
cause diseases in the walnut tree.
Walnut diseases caused by fungi and bacteria
- Marssonina leaf spot disease
- Bacterial walnut brandy
- Real powdery mildew fungus
- Mushrooms of the genus Nectria
These four diseases occur on the trunk and bark and provoke the development of bark cancer.
- Shaggy Schillerporling
- Scaly porling
- Ash tree sponge
These five species of fungi are wide-host pests. You are responsible for wood rot.
Walnut tree diseases caused by insects
- Walnut felt gall mite
- Striped walnut louse
- Woolly cup scale louse
These three insects cause leaf damage. They can cause stunted growth in young plants.
- Willow borer larvae
- Blue sieve larvae
These two genera cause structural damage to the trunk of the walnut tree.
The maggots of the so-called walnut fruit fly are also a typical problem.
Note: In addition, Phytophtora can damage and degenerate the roots of walnuts. Phytophtora is a genus of plant-damaging protists. These are microscopic living things. Symptoms of a Phytophtora disease: stunted shoots, yellowed leaves, light crown.
A portrait of selected walnut tree diseases
Marssonina leaf spot disease (the most common walnut tree disease) is given in a separate article. Here we want to focus more intensely on bacterial walnut blight and the walnut fruit fly - two other diseases or pathogens that often occur.
Bacterial walnut brandy
Bacterial blight is a walnut tree disease that can be found both in Germany and in other European countries.
Rain and wind ensure the bacteria spread. Gaps, cracks and other wounds on the leaves and on the wood allow the pests to penetrate - moisture acts as a catalyst.
The bark of the walnut tree is usually attacked in autumn. From the following spring the plant shows signs of
- Bark cancer (wood growths) or
- Bark brandy (dark bark, top layer peeling off).
The leaves of the walnut show light spots. As a result, they turn brown. Finally the leaves fall off. Affected flowers look burnt.
Here's how you can fight (or prevent) bacterial walnut blight:
- plant resistant varieties
- Avoid nitrogen-rich fertilizers
- Regularly thin out the crown
- only cut with disinfected tools
- Carry out pruning on dry days
- Cut off affected areas into healthy wood
- DO NOT dispose of infected plant parts on the compost
Walnut fruit fly
Walnut fruit flies are insects that lay their eggs in the walnut fruits. Up to 30 larvae hatch in it and eat their way out through the pulp. Fortunately, the actual walnuts remain intact and are still safe to eat.
Note: In commercial agriculture, infected nuts have to be cleaned at great expense in order to be salable.
Here's how you can combat (or prevent) the walnut fruit flies:
- Pick up walnuts daily
- From mid-June, place a tight net under the tree crown
The second measure prevents the maggots from hatching. In hot summers, fruit flies even perish under the warm net.