Grey Leaf

The Lawn disease Grey Leaf or Grey Leaf Spot (GLS) occurs rather rarely in Germany. But when it does, it is usually in soccer stadiums or on nearby training pitches.

In this disease, the leaves are massively affected by gray leaf necrosis and thus destroyed, at least locally. Photosynthesis and material transport in the tissue are no longer possible as a result. The consequences of this are sometimes drastic and often lead to a large-scale loss of the sward, meaning that it has to be completely replaced.

Infestation with Grey Leaf requires not only a higher temperature but also prolonged leaf wetness. The optimum temperature for infestation is between 28° and 32°. However, the air temperature alone is not decisive for leaf infection. It still requires the combination with moisture (leaf wetness). At the optimum temperature (28°-32°), a leaf wetness period of 9 hours is required. At a suboptimal temperature (20°-23°), however, 21-36 hours. The prerequisite is that leaf wetness is maintained over this time. Lawns that are supplied with a lot of nitrogen are particularly susceptible to grey leaf infestation.

The Lolium species L. perenne and L. multiflorum as well as tall fescue (Festuca arundinacea) are particularly affected by infestation. Poa pratensis is not infested.

In invalid periods, the fungus survives as mycelium in dead plant material (e.g. lawn thatch). When the conditions for the development of the fungus become optimal again, it returns. If mycelium remains of the fungus adhere to shoe soles or tools, the disease can also spread to other lawns. However, this is also possible through wind and water.

The disease can be prevented by

• ensures the optimum nitrogen supply in the lawn. Avoid excess nitrogen and readily available forms of nitrogen.

• Optimize the irrigation technique (watering early in the morning rather than in the evening)

• keeps the lawn dry

• mows regularly and picks up the clippings

• Do not carry out reseeding in case of active infestation