Lawn Disease

Lawn Disease

Red Thread, Fusarium, Leaf Spot, Dollar Spot, Anthracnose and Rust are all lawn diseases. They can all affect the grass plant, causing discoloration, weakening the plant, and ultimately killing it all together. Most of these diseases are caused due to stress on the lawn - whereby the plant is: (a) not being cut correctly; (b) it is not receiving sufficient water; (c) thatch levels are too high; or (d) the lawn is compacted. The environment can also play a part - for example, humidity will affect the plant along with too much water sitting on the leaf of the plant. Control is achieved by cultural means or, if necessary, using a fungicide to correct some of the issues which may increase the stress, thus causing the disease.

Diseases in lawns are commonly caused by the presence of a fungus and are often termed pathogenic agents of disease. Disease pathogens are already present either in the thatch or basal leaf, awaiting the right conditions to break out. The disease known as Red Thread has a fungus called Laetisaria fuciformis, Fusarium has the fungus known as Michrodochium nivale. These are the most common lawn diseases we find in UK lawns. There are many others, some are listed above. The treatment of these diseases can be related to their cause, so the cultural process is probably best for the plant. If it works successfully, then the lawn is fully restored without the use of products which may be best saved for when the cultural process has been ineffective.

The sprayed product we recommend is taken from other fungi to act as an agent to protect the plant; the product works its way into the plant via the leaf and root system; it will control the disease for generally about one month. If the cultural processes have been followed, then it is likely you will have control for longer. We have two different fungicides, one for the growing season and the other for when the plant is dormant.

Having a good programme of lawn care i.e. regular feeding, weed control, aeration, scarification and moisture control, along with good cutting practices, will help to keep the lawn balanced and reduces the risk of disease.

Snow Mould

Very closely related to Microdochium Patch (Fusarium) is Snow Mould, another cool weather disease that thrives in lawns with poor air circulation. This fungal disease spreads rapidly during cool weather, especially under a blanket of snow, where there is no air circulation. When snow settles on a lawn for any length of time, it incubates the disease which can only be seen once the snow has melted.

The fungus produces white, dish-like patches which, in severe cases, can turn pink. It is not possible to keep snow from the lawn so be prepared to deal with this once the snow has melted. What will help is to get the air moving in the lawn as quickly as possible so a hollow-tine aeration can help, along with an application of a micronutrient to help the grass. The other option is an application of a fungicide which will stop its activity and, as the weather improves then, if necessary, action can be taken to help with the recovery of the lawn.

Microdochium Patch (Fusarium)

Microdochium Patch (Fusarium) is another very common lawn disease, seen mainly, but not exclusively, during the autumn and winter months. This is a cool weather disease and enjoys persistent drizzle and foggy/misty conditions with low air movement.

Symptoms appear as small, circular, yellow patches which can spread up to about 30cm in diameter. Once established, the patches turn a yellow/brown colour and in severe cases can kill the grass. After the disease becomes inactive, the area appears pale and straw-like.

Lawns that have a high thatch layer and poor drainage, as well as enclosed lawns with little air movement, are the most susceptible to this disease.

Leaf Spot

Leaf Spot is a very common lawn disease that affects lawns across the UK. It can also be known as leaf blight or net blotch. The disease can be caused by numerous different fungi and spreads rapidly. Warm and humid weather conditions are favoured by this disease and spores of the fungi are disseminated by water splash.

A stressed plant is more likely to be affected than a healthy one, so ensuring the grass is well fed and watered will help. Also ensure the mower blades are sharp and do not cut the grass too short. If the lawn suffers from thatch, consider having machine work - Aeration and Scarification will help to keep the sward healthy, thus reducing the likelihood of disease.

There are other pests that you may come across, and your local operator will be able to advise you accordingly.

Fairy Rings

This lawn disorder can appear as complete circles, ribbons or arcs of stimulated grass growth, which may or may not be associated with bare areas of turf and toadstools.

There is not always a specific reason as to the cause of a Fairy Ring, although very often it is caused by rotting wood or root in the soil. As the wood rots, it develops mycelial spores that work their way up to the turf surface.

The mycelium will affect the soil, making it hydrophobic; this means the soil tends to be water-resistant and this exacerbates the problem. Fairy Rings are very difficult to treat, but if your lawn is affected with this problem, we will be happy to advise and recommend a treatment and a course of action which helps with control.


This is possibly one of the oldest known turf diseases. It attacks the leaf plant and causes extensive damage. It rarely attacks the whole plant, so recovery is usually good.

This disease thrives on plants suffering from stress, and is most prevalent in autumn or early spring, when the weather is warm and wet.

If your lawn is looking under the weather, tired and not the right colour, speak to your local GreenThumb expert who will be able to offer great advice and solutions.

Red Thread

Red Thread can be seen through late spring and summer months during periods of high humidity. It occurs mostly after periods of wet weather, especially towards the end of summer, when humidity is high.

The lawn will begin to show small patches of grey-brown turf initially; on closer inspection, the grass plant will have small, red ‘needles’ protruding from the diseased leaf.

Although high humidity is the main cause of Red Thread, it can also be seen in lawns that are suffering from plant stress. This is usually caused by: poor cutting regime, drought, thatch, compaction, or lack of feeding. By ensuring a good care programme of feeding, cutting with a sharp blade on the mower, thatch reduction and aeration, this will help to keep it in check.

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  •  "I am a relatively new customer but I wish to thank you for the great job you have done on my lawns. In six months they have gone from green/yellow to a lush green appearance with few weeds and moss. Well done GreenThumb from a very satisfied customer."

  • "We've now had two treatments from your service. Already we have noticed a difference in the quaility of the lawn and the greenness. Really pleased. Also, the young men who have visited have been charming - very polite and pleasant, thank you."

  • "When we moved into our house five years ago, the whole garden was very overgrown and the lawns were in a dreadful state. After only two years our front and back lawns have been dramatically transformed, I would highly recommend GreenThumb to anyone."

  • "We bought a new property and the land had previously been used as a pig farm so lots of strong weeds. We are now a year in from the start of your team's treatment and the improvement is 200%. The team in Norwich always arrive on time, are courteous and are very well informed."

  • "The grass is lush, thick, green and plentiful. Even the front which was an eye sore has received compliments. We are delighted with what has already been achieved and only wish I had known about this service sooner. I could have saved myself a lot of time and effort."