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Mainly during the summer months, a brownish and later reddish discoloration of the lawn plants can sometimes be seen on lawns. It doesn't look very pretty, but there's no need to panic. This is just one of the most common lawn diseases, red thread. There is no danger to the lawn itself. The lawn plants are not damaged. Below you will find more information about the causes of the outbreak and how to combat it.

Typical summer illness?

The disease of the lawn plants usually occurs during the summer months, which is why red thread is considered a typical summer disease, which is also known under the name red thread. However, that is not really true, because lawn disease can also occur in spring and autumn. In principle, lawn areas can become infected from April to October, always depending on the prevailing weather. The disease rarely occurs during the winter months, since the red tip does not tolerate frost.

The green is then a bit unsightly, but it looks worse than it is. There is never a risk of the lawn plants dying off. The disease usually goes away on its own, as quickly as it came. Appropriate weather conditions are crucial. Sports turf is just as susceptible to this lawn disease as the lawn in the garden. are particularly affected

  • Common red fescue (Festuca rubra)
  • bent grasses (Agrostis)
  • Meadow grasses (Poa pratensis)
  • Ryegrass (Lolium)

fungus as the culprit

Red thread is caused by weakness parasites in the form of fungi

  • Corticium fuciforme
  • caused by Laetisaria fuciformis.

However, there are various reasons why the fungus can spread unhindered on the lawn. This can be due to care errors, but the prevailing weather conditions are also decisive for the spread of lawn disease. Inadequate care weakens the lawn and makes it easy for the fungus. This includes

  • nutrient deficiency
  • mainly nitrogen is missing
  • Lawn covered in moss and matted
  • poor aeration of the lawn
  • wrong watering
Torben von Elling -, red thread, edited by Plantopedia, CC BY-SA 3.0 DE

The emergence and spread of red thread is then favored by unfavorable warm and humid weather over a longer period of time. Various factors are decisive here

  • high humidity
  • Temperatures between 16 and 20 degrees Celsius
  • fog and morning dew

However, prolonged drought can also be fatal. During this time, growth stops and the leaves lose their resistance. If the leaves of the plants then become damp, the risk of infection is increased.

Tip: Morning dew can favor the development of the fungus. With small lawns, wiping off the rope can be helpful.

Recognize the first signs

Initially, straw-yellow to light-brown areas with a diameter of up to 30 centimeters can be seen on the lawn. The grass plants make a dried up impression, despite the existing moisture. The irregular brown spots spread further down from the leaf tip. At this point, the disease may not be fully identified. But these signs don't stay that way for long, and then there is a pink-colored mycelium:

  • cotton-like reddish down around the leaf tips
  • stuck sheets
  • occurs especially in the morning

A spherical star-shaped red fruiting body can be seen with the naked eye.

Control and preventive measures

Normally there is not necessarily a great fight against the red thread in the lawn. Sometimes dryness helps. As a rule, the disease disappears on its own very quickly in dry weather. There is no danger from the red tip. With the right lawn care, the grass plants are stimulated to sprout again after an infestation with the fungus. In addition, the formation and further spread of the fungus can be prevented. Good care, control and prevention include:

Good nutrient supply

A long-term fertilizer should be used here. This must contain mainly nitrogen, potassium and phosphorus. With an additional administration of nitrogen, the disease can be "treated" in the case of an existing infestation. After just a few days, the fungus infestation is no longer visible. In addition, fertilization should be carried out regularly throughout the year, which would be optimal

  • 5 g nitrogen per fertilization five times a year
  • first fertilization at the end of February to mid-March
  • last fertilization in late autumn
  • no fertilizer application between October and February

At the end of February it can still be a little too cold for growth, but after a short time the lawn shows a beautiful color and the plants become more resistant to stress, which also reduces the susceptibility to red thread.

Water properly

Finding the right balance of watering is important. Too much moisture can accelerate fungal growth. After long periods of drought, the lawn urgently needs moisture. But there is no point in turning on the sprinkler every day. Therefore it is advisable

  • water once a week
  • longer and more penetrating
  • water preferably in the morning

When watering in the evening hours, there is a possibility that the blades of grass cannot dry completely. This in turn creates an ideal microclimate for the red tip.

Aerate the floor regularly

Air must be able to reach the roots of the lawn plants regularly so that they are strengthened and permanently protected from diseases. Waterlogging is also avoided by regularly aerating the soil. There are special devices for this. Alternatively, a simple digging fork can also be used. Holes are made in the ground at intervals and then filled with sand. The lawn should also be scarified to remove thatch, moss and weeds. These residues are a major source of infection of this disease. The best time for this is

  • in spring (March/April)
  • in autumn (September/October)

Proper lawn mowing

A lawn that is cut too short is always susceptible to various diseases, including the development and spread of red thread. Mowing too often can also cause damage. A cut that is too deep should always be avoided, as the plants are then not able to absorb the corresponding solar energy. In this case, the growth must be stimulated by its own efforts, which in turn can lead to a weakening of the plants and they are therefore more vulnerable. Furthermore, care should be taken to ensure that the blade of the mower is sharp to prevent additional injuries. There the fungus could enter unhindered. is recommended

  • Cutting height maximum 3 cm
  • in the shade 5 cm

Notice: Hedges and walls in the immediate vicinity of the lawn keep the wind away. This makes it more difficult for the lawn to dry out and can promote the development of the disease. Leaves should also be removed from the lawn regularly. Here, too, a bad microclimate develops.

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