Lawn diseases - prevention, symptoms and control

Common lawn diseases

Fairy Rings
The symptoms include one or more of the following: rings of lush grass, rings of toadstools or puff balls, areas of dead grass between the lush rings. Fairy rings are caused by the effects of a fungus that forms a barrier in the soil. Treatment of fairy rings is difficult and often will need the area of lawn to be repaired.

Red Thread
The symptoms include the colour of the grass changing to a bleached colour followed by red / pinkish threads appearing on the grass stems giving a pinkish appearance to the lawn. Red Thread is caused by another fungus and results in patches (varying in size) of withered and dead grass. A large contributing cause is lack of Nitrogen in the soil. Feeding the lawn can therefore help prevent the onset of red thread.

Dollar Spot
The symptoms are circular spots of straw-coloured grass with the spots being about 15cm in diameter. Dollar spot is the result of a fungus that can be seen in the morning when the dew is still on the lawn. The fungus has the form of a cobweb type appearance. Lack of soil fertility is a large contributing factor to Dollar Spot.

Toadstools / Puffballs
Some people may find some varieties of toadstool visually appealing (especially in a woodland garden environment or when there is a garden gnome or two around). Toadstools / puffballs can be in a number of shapes, sizes and colours but all require similar growing conditions. Fungus must have the correct conditions for growth and toadstools / mushrooms / puffballs will grow where there is decaying organic matter such as old decaying roots / broken branches / fallen leaves. Fungi also love moist, damp conditions to improving soil drainage and preventing the build up of thatch will help prevent the onset of toadstools.

Rust
Symptoms include a change in lawn colour ranging from light green to yellow. Yellow / brown spots may appear on the grass blades in late summer. Orange powder will occur from the infected grass. This fungus will thrive in warm damp conditions and heavy dew can be a contributing factor. Prevention of the onset of rust includes feeding the lawn as lawns that have a Nitrogen deficiency are much more susceptible.