Although snow mold (Gerlachia nivalis) allows a different interpretation, it is not a true winter disease and is not bound to snow or frost. With high humidity and cool weather (temperature optimum 0-8 °C), infection can occur almost year-round. Only temperatures < 0 °C and > 20 °C inactivate the pathogen. At temperatures of 3 °C, snow mold is the most important pathogen on turfs.
In contrast to Typhula blight, snow mold is a wet rot. At the beginning of the infection, small, watery gray spots of 4-6 cm in diameter appear. As the disease spreads, diameters can reach 25 cm, with the spots running into each other. A dark brown border may form at the edge, the active zone of infection. In high humidity, a dense, cotton wool-like, gray to pink mycelium appears. This is the origin of the English name „pink snow mold“. Regeneration of the infested areas occurs from the center of the spots.
Changing temperatures (cold/warm periods) can promote infestation with snow mold. In this case, the grasses do not go into proper winter dormancy, which forms a natural protection against disease infestation. Prolonged moisture such as dew, fog and a poorly drying soil surface promote the development of the fungus. A lack of air circulation also creates an ideal development climate for infection. Ideal starting points for infestation with snow mold are also leftover leaves, mulch or cuttings in which the mycelium survives. A high pH value at the soil surface promotes the development of snow mold. One-sided high nitrogen applications in autumn and neglected potassium supply cause a weak tissue structure, which is a breeding ground for the pathogen.
As the control of snow mold with fungicides is becoming increasingly difficult due to legal regulations and the lack of active substances with turf approval, the following preventive measures are becoming more and more important:
After the lawn Dispose of the dead material that has been pulled out.