Identifying and Controlling Turfgrass Diseases

Common Turfgrass Diseases

turfgrass diseases

There are quite a number of turfgrass diseases, and ironically the better the turf and the more closely it is cut the more likely you are to attract one or more of them; so much so they have been described as man-made. Of the many diseases the three most common are fusarium patch, corticium, sometimes called red thread, and dollar spot. Of these three, two are late-summer and autumn diseases but can, like every other fungus disease, show themselves any time conditions are suitable.

Fusarium or snow mould is one which is likely to appear after the winter or where snow has been lying on the grass, but the other two may be expected at any time, especially after the moist, muggy weather generally experienced in July.

Dollar Spot

This occurs on turf grasses virtually all over the world and the name was derived from the occurrence of dead bleached spots about the size of a silver dollar. The spots rarely get beyond that size but if not controlled they can become so numerous that they tend to join up and overlap resulting in large irregular areas of dead turf. They are particularly visible in the early morning when the grass is damp with dew and at this time wisps of the white threads of mycelium can be seen on the tips of the grass blades. The sun and the wind will dry the grass and the mycelium but it can persist in the cool beneath the grass blades. The disease gains entry through the cut leaf tips and if treated early can be prevented from travelling down, eventually to kill the whole plant.

dollar spot Blunt, badly set mower blades, especially of rotary mowers, can chew the tops off the leaf blades causing them to become whitened and so make it easier for the fungus to settle and attack.

Disease development is usually most rapid when the temperatures are fairly high, around 2l°C (70°F) but, unfortunately, there are various strains of the fungus which can operate at lower temperatures. It is worse on lawns which have been starved but the resistance of grasses to fungus disease is significantly increased where the plants have received adequate nitrogen. Fortunately, dollar spot is not a disease that destroys grass quickly, especially if adequate nitrogen is provided. Personally, I find the best way of applying a nitrogenous fertiliser is in liquid form, such as a good soluble foliar feed.

If the soil is dry it should first be wetted before the fertiliser is applied. Unfortunately, however, mowing without a grass box or using a rotary mower may cause the rapid spread of the disease. If it does develop, try to avoid walking on the affected spots. There are a number of fungicidal compounds available suitable for controlling dollar spot and one of these should be applied without delay, according to the directions on the pack.


Also known as red thread, this is one of the turfgrass diseases of spring and summer and is especially prevalent during cool wet weather. It is readily identified by the coral pink gelatinous and sticky masses formed by the fungus on leaves and the sheaths of the grass plant. This jelly-like coating is often joined with a pink web of mycelium which, like dollar spot, is very conspicuous when the grass is wet.


This disease will affect the leaves and the sheath, which is the point at which the leaves join the Stem. The grass rapidly dies and takes on a light tan colour when dry. Corticium is easily spread by walking on the grass, by birds, animals, on the mower, by wind and various other agencies.

Here again the application of nitrogenous fertiliser and prompt treatment with a suitable fungicide will clear up the trouble within a matter of weeks. The most important thing about all these diseases is to recognise them quickly and act promptly.

If you have nothing else available, use the same sort of fungicides that you would spray on roses. This is better than nothing, especially if otherwise you have to wait until you can go into town to buy a turf fungicide specially for that purpose.

Pythium Blight

pythium blight Another one of the annoying turfgrass diseases which you may often find on new grass, or newly-sown lawns, is one of the pythium blights. This is the same sort of trouble which gardeners call ‘damping off’. This disease is favoured by cool wet days followed by a burst of sunshine and it is more active where there is an abundance of moisture and the plants are wet. Heavy dews, high humidity, muggy weather all favour its spread. Pythium blight does not seem to respond readily to the ordinary turf fungicides, but I have found that Cheshunt compound, also used against damping off, and permanganate of potash, give good control.

A lawn that is well fed and where the grass plants are kept in reasonable condition is much more resistant to diseases and, if it does become attacked, it grows away much more quickly than one containing starved grasses. The recent introduction of a long-lasting lawn feed will be found to be a boon to those gardeners who always mean to feed the lawn but never get around to it. This fertiliser contains quick-acting ingredients and a proportion of slow-release nitrogen and other plant foods which are given up over the whole of the season, so that one quick application provides sufficient plant food for the rest of the season.

Another of the more common turfgrass diseases is Fairy Rings – read more about Fairy Rings.

06. August 2010 by Dave Pinkney
Categories: Lawncare, Lawns | Tags: , , | Comments Off on Identifying and Controlling Turfgrass Diseases


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