Fusarium Patch - Snow Mould

Fusarium Patch - Snow Mould
The disease it causes was known as snow mould because it was most often associated with cold, wet weather in spring - damage would be revealed when snow cover melted.
However, the fungus can damage turf whenever conditions are cold or frosty and wet. It has now become much more common in autumn than spring and is known as Fusarium patch when its appearance is not correlated with snowfall.
Identifying the disease
The fungal mycelium is pale pink in colour and, when massed together, lends a distinctly pinkish tint to the surface of the affected turf, especially at the edge of an infected patch, where the fungus is actively growing and producing spores. It grows on dead material in the thatch layer until conditions enable it to infect living turf. Infection is favoured by cool, wet weather or frost alternating with cold and wet.
Symptoms
In the early stages of infection, grass plants start to become slightly paler in colour. Infection progresses to produce small patches - about 2cm in diameter - of dark-brown or olive-coloured grass with dark, slimy or water-soaked leaves.
Infection spreads to form patches 30cm or more across with brownish or greyish dead grass in the centre. Grass at the edge of the patch is water-soaked or slimy with white or pinkish mycelium matting the leaves together. The pink mycelium is often easiest to spot early in the morning. If allowed to spread unchecked, individual adjacent patches merge to form large, irregular infected areas.
Treatment: cultural control
- Prevent the base of the sward remaining wet by ensuring adequate drainage with regular scarification and aeration.
- Remove and prevent thatch, which harbours the fungus and retains water and humidity.
- Use acidifying fertilisers and aim for a pH of around 6.5.
- This pathogen prefers alkaline conditions. Iron sulphate acidifies the surface and hardens the leaves, making them less prone to infection.
- Applying high-nitrogen fertiliser late in summer or going into autumn causes lush growth that is more susceptible to attack.
- Keep grass short going into winter.
- On fine greens, brushing to remove dew is worthwhile. The risk of spreading spores is outweighed by the benefits of removing the conditions they need to germinate.
- Time irrigation to pre-dawn or early morning to knock dew off leaves.
- Judicious pruning of overhanging or adjacent vegetation to reduce morning shade and increase air movement over the surface helps to dry turf more quickly.
- Good aeration, balanced nutrition, regular scarification and prompt attention to surface drainage problems encourage good microbial diversity in the root zone, helping to reduce the amount of thatch and organic matter on which the pathogen lives.
Soil microbial diversity can also be encouraged by the use of bio-stimulants such as seaweed-based fertilisers and compost teas.
This article is a condensed version of an article in Horticulture Week on this subject