Marssonina disease in the walnut tree

Portrait of Marssonina leaf spot disease

Marssonina juglansis, as the Latin name of the disease is, is also known under the names of walnut scab, leaf tan and anthracnose.

The pathogen Gnomonia leptostyla acts as a trigger. Interesting fact: This pathogen was originally called Marssonina juglansis and gave the disease its name.

Like every mushroom, Gnomonia leptostyla also thrives particularly abundantly in damp weather and moderate to warm temperatures.

Symptoms of Marssonina Disease

First of all, the appearance of the leaves and pods changes. Similarities to another Walnut Tree Disease, the walnut bacterial blight, cannot be dismissed out of hand in the early stages.

In both diseases, brown, angular spots appear on the leaves and fruit coats. These spots get bigger quickly until they cover almost the entire leaf or the entire fruit and eventually even run into one another.

Light centers are usually revealed in these brown spots. The brown areas look like they have been burnt and are so dry that the tissue partially breaks out and only leaf veins and stems remain. Sometimes the leaves also fall off.

On the underside of the leaf there are small black-brown, ring-shaped points with a typical spore appearance. This collection of spores enables it to be differentiated from bacterial burn.

If the fungal infestation is severe, this weakens the entire walnut tree, which can also lead to premature fruit fall. However, the direct effect on the walnuts is much worse: the spores attack the green one Fruit skin and often penetrate to the core (especially with young fruits with soft wooden skin) - the Result are

• a black wooden bowl,
• an infected nut kernel and
• Dry rot.

Good growing conditions for the fungus

• humid spring and summer
• Rain shower and wind *

* Rain showers and wind "help" wash off and spread the spores.

Incidentally, here (in contrast to bacterial fire), older leaves are much more susceptible than young ones - they provide the spores with more breeding ground.

Fight Marssonina disease in a targeted manner

• Carefully collect the leaves and fruits of infested walnut trees.
• Do NOT put the collected plant parts on the compost, but burn them if possible or otherwise throw them in the organic waste bin.

Prevent Marssonina leaf spot disease

By regular Cut prevent this walnut tree disease.

You should also be at New plantings always choose varieties that have a basic resistance to the pathogen (Gnomonia leptostyla).