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Dollar Spot lawn disease

Dollar Spot lawn disease showing in a Bermuda Grass lawn

With the right lawn care program, Dollar Spot should not be a problem. It is more often or not the result of a neglected lawn.

Dollar spot is a serious lawn disease as it can affect and kill the whole of the grass plant including the roots. This means that affected areas of the lawn will often need reseeding.

Dollar spot will infect a large number of different grass varieties.

Dollar spot symptoms

As its name suggests Dollar Spot is a lawn disease that results in tan / grey spots appearing on your lawn. These spots can vary from 1 to 6 inches in diameter. They can also overlap and merge to form larger patches of diseased lawn.

The fungus that causes dollar spot will result in the grass blades having tell tale tan coloured legions with red / brown edges.

Dollar spot causes

Dollar spot is caused by a fungus. The fungus survives over winter by taking hold on plant matter that appears in the layer of thatch that occurs in the lawn, it also inhabits plant matter in the soil. In winter time the fungus is not actively growing but when the warmer temperatures (70-90° F) are reached in spring the fungus will start growing and spreading.

So what are the environmental conditions that are ideal for growth of the fungus and therefore the source of the cause of dollar spot?

  • Lack of soil moisture - dollar spot will thrive in lawns which aren't watered properly. A low soil moisture content will help dollar spot continue its advance.
  • Lack of Nitrogen - lawns require Nitrogen for leaf growth and a lawn that has adequate nitrogen levels in it will be more vigorous and resistant to disease.
  • High levels of thatch - thatch prevents water penetrating into the soil and provides good conditions for the disease to survive over winter.

Another contributing factor to the onset of dollar spot is mowing the grass to too short a length in dry periods when there are slow rates of grass growth. The lawn is more at risk from disease and weed infestation at these times.

The disease is spread across the lawn by foot and vehicle traffic, watering, rain and dew.

Treatment of dollar spot

As with nearly all lawn diseases prevention is better than the cure and if you follow a good lawn care programme then you should not be bothered by this problem.

Watering the lawn at the correct intervals is one of the keys to preventing dollar spot as it will help the soil retain moisture. Remember it is best to water thoroughly at intermediate intervals rather than watering sparingly at short intervals.

You should aim to water the lawn in the morning as the grass should be dry before nightfall so that optimum conditions for fungus growth are avoided. Dispersal via water is one of the ways that the disease travels across a lawn so watering should be done with care.

Removing / reducing the layer of thatch will help water penetrate the lawn and reach the soil. Use a lawn scarifier every autumn to dethatch the lawn.

Ensure your lawn has adequate nitrogen levels by applying a suitable lawn fertiliser at the correct intervals.

As a last resort Fungicides are available for the treatment of dollar spot.

Because dollar spot can kill the whole of the grass plant you may need to reseed areas of the lawn even if you have eradicated the dollar spot.