Summer lawn diseases and how to treat them

Our guide to identifying and ridding your lawn of diseases this summer.

One of the many requirements for looking after your lawn during the summer months is the management of lawn diseases. The type of disease that can cause problems for your turf can vary depending on a multitude of factors, including the condition of your lawn.

Here are our tips for spotting and dealing with some of the most common offenders.

Red Thread

Red thread is one of the most common turf diseases you might find in the UK, partly because it can re-occur multiple times in a single year as the fungus spores in the soil can remain active for up to 2 years!

Part of this vitality is due to red thread’s ability to survive at temperatures as low -20°C or as high as 32°C – but is most commonly active from late spring and through to the autumn. It can develop on most grasses, but ryegrasses, fescues, and annual meadow grass are more commonly infected.

Red thread is common on lawns during wet summers, when humidity is high and nutrient levels are low. Red thread will rarely kill the grass completely, and the patches will recover with appropriate remedial action.


To identify red thread, be on the lookout for countless strands of very pale pink fungal mycelium which grow out of the leaf tissue and become wound tightly together, which has the effect of making them appear red. The development of these needles, or mycelium adds to the infection as it allows the disease to spread over the lawn surface, especially during humid conditions.


Red thread is often referred to as an indicator of low fertility and the symptoms are especially common with a reduced level of nitrogen available to the plant. And though red thread is almost invariably a leaf disease, and despite the fungus having the ability to enter and damage the crown tissues, it very seldom does. Because of these factors, the symptoms of the disease can frequently be reduced by balanced applications of fertiliser, and the removal of the infected leaf tissue by boxing off the clippings during mowing. However, because red thread can re-occur, it isn’t guaranteed that one treatment will resolve the problem. The disease can be spread by infected clippings and direct movement of the fungus underfoot or by machinery.

Leaf Spot

Leaf spot usually occurs when temperatures are high and conditions are humid, especially in areas of the lawn that are shaded. Minor infection may result in lesions on the leaves. The infected area is normally brown in colour and as the infection progresses the colour of the surrounding tissues will also change. This has the effect of often making the grass blades appear as if they have been partially burned. As with other turf diseases, the leaf tends to turn a pale brown or tan colour. Results of the infection can vary, but if it moves down and reaches the leaf sheath it can result in thin strands of grass. If the infection reaches advanced stages where many plants die in large patches, it is known as ‘melting out’. In the early stages of infection, it should be noted that it can often be difficult to tell the difference between leaf spot and insect damage. This is a bigger problem than you might think, as watering a lawn damaged by leaf spot a can encourage the spread of the disease!


So how should you treat leaf spot? As with any other lawn disease, if your lawn has been infected with leaf spot, the best thing to do is act right away and contact your local TruGreen Lawn Care Specialist.

Of course, you can help to prevent leaf spot by maintaining a grass-cutting height that isn’t too short. This is because grass with longer, stronger blades is better resistant to damage.

Like red thread, leaf spot can also be effectively dealt with through the application of fertiliser. The right application of nutrients to the soil during a leaf spot infection can entirely kill off an infection. But because water can encourage the spread of leaf spot, remember to avoid over-watering affected areas. It may also be advisable to then aerate your lawn to increase air and moisture reaching the roots of the plant.


There are lots of different diseases that can affect turf grasses, and like red thread, some grass species are more susceptible to damage. The more at-risk grass species are Perennial Ryegrasses and Smooth Stalked Meadow grasses.


It is important to be vigilant in the mid to late summer, as this is the most common time of year for infection to occur – As with other turf diseases, humidity, low fertility and infrequent mowing regimes are common causes. Grass infected with rust is so-called because it often appears rust-coloured due to the production of yellow and orange spores on the leaf surface.


Like the other summer lawn diseases, control of rust infections can be achieved through adequate fertiliser application, regular mowing, and if necessary the use of a fungicide.

One thing that can be identified about the most common diseases, is the importance of balanced fertiliser application and mowing habits. If you’re worried about the spread of lawn diseases, there’s no better time to begin a discussion about a quality treatment plan for your lawn this summer with TruGreen professional lawn care.

Booking a 14-point lawn analysis now means you receive a no-obligation assessment of your lawn from the experts. Whether it is to keep your lawn healthy, and put your mind at ease, or start out on the road to recovery, get the help your lawn needs by finding your nearest TruGreen business today.

Written by Tom Page, Digital Content Writer