Lawns can become susceptible to fungal diseases for a variety of reasons. Common reasons for a fungal infestation are poor drainage (i.e. the air can no longer circulate sufficiently), excessive moisture and/or incorrect nutrient content or soil pH. In addition, some grasses are more sensitive than others, for which sometimes rainy weather is enough.
Fungal diseases are often noticeable through patches in the lawn
Causes of fungal infestation and what you can do about it
Most fungal diseases arise from poor ventilation and high humidity. However, you can reduce the risk by regularly scarifying the lawn to prevent or remove thatch. Air circulation can also be improved by cutting overhanging trees. With a lawn mower or a thin bamboo stick, you can (especially in the morning!) remove excess moisture from the stalks, while aerating loosens compacted soil and allows air to get to the roots.
Mow and clear the lawn regularly
Regular mowing will keep the grass healthy and strong while cleaning up the clippings. This measure prevents the accumulation and spread of fungal spores, which thrive in the typically moist environment of mulch material. In autumn you should also not fertilize with too much nitrogen. This would encourage overly lush growth, which in turn is susceptible to snow mold, rust, and other fungal diseases.
Which fungal diseases occur in the lawn?
snow mold
The fungal disease caused by various fungal pathogens usually occurs in the cold season, especially after a rapid fall. Yellow or brown spots appear in the lawn, which have a reddish-brown edge and are sometimes covered with a cobweb-like white coating. The risk of disease is reduced by regular scarifying and moderate nitrogen fertilization.
redness
Red spray is caused by the fungus Laetisaria fuciformis and is shown by blades of grass that are initially red and later brown. The disease leads to the death of the lawn, whereby the pathogens lie dormant in the soil in the form of sclerotia for years and can break out again at any time. Red splashing often occurs after wet summers and autumns, and it can also be caused by a lack of nitrogen.
dollar spot disease
The fungus Sclerotinia homoeocarpa is responsible for this disease, the mycelium of which attaches itself to the leaves but does not penetrate the soil. The first signs are small, straw-colored spots that gradually spread. Lawns are particularly at risk in late summer or autumn on compacted soil and on soil with a high pH value.
Brown patch
The Rhizoctonia solani fungus needs warm, humid conditions and therefore occurs mainly in early and late summer. It penetrates both the roots and the leaves and first appears in the form of brown spots on the blades of grass. In the case of a severe infestation, the fungus spreads extensively and leaves behind light brown, withered grasses. An infestation can only be prevented by good lawn care.
witch rings
Cap mushrooms growing out of the lawn in a semicircle or circle are called witch rings. These are the fruiting bodies of an underground mycelium that grows outward from the center of the circle. Dig the entire area deep and replace the soil - this is the only way to permanently remove the mycelium.
slime molds
Slime molds mainly appear in late summer and autumn. They don't actually damage the weed but are quite unsightly. There are no countermeasures, but you can reduce the risk of infestation by regularly aerating and scarifying. The fungi can be removed by hosing down with a jet of water.
tips
Fungal spores can not only be blown by the wind or brought in by animals, but can also be spread by poorly cleaned tools and machines. You should therefore (especially with rental devices!) ensure good hygiene and thoroughly clean and disinfect all tools before and after each use.