Why do trees have stems

Discolored trunks are harmless to trees, humans and animals - Algae rust trees

However, it is not a tree disease, announced the Lower Nature Conservation Authority of the Teltow-Fläming district in response to a MAZ request. The discoloration on the trunk does not indicate that the tree will soon die, as many hobby gardeners fear.

Microalgae are harmless to the tree

"The reddish deposits are red microalgae," says Achim Sommer, biologist at the Lower Nature Conservation Authority in Luckenwalde. The phenomenon is known to him. There is no need to worry. "The algae are completely harmless to the tree, humans and animals," he says. The authority sees no need for action to treat affected street trees. It is to be expected that the deposits will regress when the weather changes and that the algae will dry out.

If you have a fruit tree in your garden that is affected, you don't need to worry about the health of the tree or the palatability of its harvest, says Sommer. “These red thread algae settle and grow only very superficially on the bark of the trunk. They have no influence on the growth of the tree or the taste of the fruit and are completely non-toxic, ”he says.

Phenomenon is particularly widespread this year

In the always damp Spreewald, this phenomenon is particularly widespread this year. But the “rusty trunks” can also be observed around Jüterbog. “This year stronger than in previous years. Because these algae feel right at home due to this year's weather. They need a lot of moisture and a lot of light to grow, ”says Sommer. Both had been sufficiently available since spring, with the rainy May. “These microalgae mostly appear on the weather side of the trees.” The heavy rain and the warm temperatures allow the algae to thrive. “This is perfect growth weather for the red algae.” But under no circumstances should poison be used, he advises all hobby gardeners. Trees should also not be felled carelessly out of concern that the "rusty surface" will spread to other plants in the garden. However, if you want, you can dry-brush the affected trunks.

Kathrin Burghardt

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