Snow mold (Microdochium nivale) in the lawn is a lawn disease that often occurs between October and March in damp and cold weather. Read our guide to find out what helps against the ugly grey-brown spots.

In a nutshell

  • no use of fungicides possible
  • Combat only by eliminating the cause
  • scarify and aerate regularly
  • Improve soil permeability with sand
  • Avoiding nitrogenous fertilization in autumn

symptoms and course of the disease

You can recognize an infestation of snow mold in the lawn by these symptoms, which usually appear after mild and rainy phases in late winter or spring:

  • initially round, brown-grey spots
  • grayish-white cotton-like patch with a dark brown border
  • are getting bigger and merging into each other
  • often similar to so-called witch rings
  • in the spring, grasses above ground are mostly dead
  • then turned yellowish brown
Source: Rasenprofi, Schneemould1, edited from Plantopedia, CC BY-SA 4.0

As temperatures rise, gray snow mold (Typhula incarnata) stops growing and heals on its own. Since the grass has only died above ground and the root system is intact, the lawn will sprout again. The characteristic spots are also gradually covered by the regrowing grass.

fungicides

In principle, there are broad-spectrum fungicides that are effective against snow mold in lawns, such as Ortiva, Saprol or Cueva. However, according to the regulations of the Plant Protection Act, these antifungal agents are not approved for use in home and allotment gardens. You cannot treat the fungal infestation with fungicides.

Tip: Horsetail broth or a strong infusion of garlic and onion, which is sprayed once a week, also helps against fungal infections. However, these are only effective in the early stages of infestation or preventively.

combat

To get rid of snow mold in your lawn, you need to eliminate the causes. Therefore, these measures have proven to be effective:

  • Thoroughly comb through the affected areas with a hand scarifier
  • scarify the entire lawn
  • aerate soil
  • Put sand or humus on the lawn and work it in

You should also provide the infested lawn with a potassium-rich lawn fertilizer after scarifying and aerating. The nitrogen content should be set lower than normal, since nitrogen-rich fertilization promotes fungal growth. It is also better not to lime the lawn, as the pathogen prefers an alkaline pH value in the soil.

Tip: After this comprehensive treatment, some areas of the lawn should be quite bare. Improve the soil with humus and sand and reseed the lawn.

prevention

In any case, the fungus disappears all by itself with rising temperatures. However, you shouldn't feel secure, as the disease will definitely come back if the weather is suitable - humid at 0 to 10 °C. Therefore, you should take good care of your lawn to prevent re-infection:

  • Scarify twice a year and remove thatch
  • aerate in spring
  • Remove fall leaves and lawn clippings
  • no nitrogen-rich fertilizer in the fall
  • mow regularly in spring and summer
  • do not mow too deep, at least four centimeters

You should also improve the permeability of the soil by sanding the area after each aeration. With these measures, snow mold has a hard time coming back.

frequently asked Questions

What is snow mold in the lawn anyway?

Snow mold is a lawn disease caused by a fungus. This is always present in the environment, but only spreads in damp, cool weather and at temperatures between 0 and 10 °C. This means that the characteristic grey-brown and ever-growing spots appear primarily in rainy, mild winters and in spring after the snow has melted.

Why is my lawn moldy?

The fungal infection also only occurs on weakened lawns that are not sufficiently aerated, for example. The causes are therefore lawn thatch, autumn leaves or clippings that have not been cleared away. Poorly drained, loamy soils are also conducive to infestation because they remain moist for a long time. Another common cause is nitrogen-rich fertilization with only a low potassium content.

Is snow mold dangerous to humans?

Occasionally, after a snowy winter, you can read in local newspapers that public lawns and sports fields with natural grass are closed due to snow mold infestation. The reason for this is not, as is sometimes assumed, that the fungus is also dangerous for humans, but because the fungal spores can be transferred to healthy lawns via the soles of shoes. So if you step on a lawn infected with snow mold, you should clean and disinfect your shoes thoroughly afterwards.

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Garden design