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  • Reece Watson

The perfect storm for the Gray Leaf Spot

We noticed that a few of our customers have been logging the appearance of Gray Leaf Spot on their field using the disease tab on the Raw Calender. The Gray Leaf Spot can be devastating for your turf. In this article we'll explain what is causing this disease and how to avoid it in the future, based on all data we've collected in our platform.


What is Gray Leaf Disease?

But first things first, some more information about this disease. Gray Leaf Disease (GLS) is a fungal disease that can occur in warm- and cool-season turfgrasses. GLS can develop agressively in young plants and 4-5 week old seedlings are extremely susceptible to infection.


The disease symptoms will vary slightly depending on the grass type affected and the age of infected plants. The initial symptoms are small, dark brown spots or lesions (1mm to 3mm diameter) on the leaf and stem tissues that may appear ‘watersoaked’. These lesions have a purple-coloured margin and may also have a yellowish zone of leaf tissue surrounding them . When the disease is active, the number of lesions on a leaf will increase and individual lesions will enlarge rapidly. Active GLS outbreaks can result in the partial or complete destruction of a stadium pitch within 3 to 5 days.


What we noticed?

A few of our customers have been logging the appearance of Gray Leaf Spot on their fields using the disease tab on the Raw Calendar. When going into detail we noticed that all users experiencing issues with GLS have logged that the disease started in the North-West zones of the field. This is an area which is normally the sunniest and the grass plant is usually the strongest.




When looking into the shade patterns of the stadiums, we can see that during mid-late afternoon, the NW area of the field falls into the shade, after a full day in the sunshine.

And, when looking at the disease risk forecasts from the Raw Weather Station, we can see that disease risks spiked mid-late July, early August and again towards the end of August in all venues. This is around the time that the high summer temperatures were recorded.




A normal reaction from Grounds Managers in hot temperatures is to increase watering and to water throughout the day rather than morning irrigation only. This means that if the pitch is being watered in the late afternoon, when the NW area is in shade, this area will sit damp at the base of the plant for a longer period going into the evening/night. All these factors combined (the shade, the high soil temperature and the dampness of the plant) created the perfect storm for the Gray Leaf Spot.


We learned a lot just by looking at the disease risk forecasting and the logging of zones where the disease is forming first, with this information we can start to see why you are getting disease, and work out how to avoid it in the future.

How to avoid this disease?

Unfortunately the disease is very had to treat, as we know so little about it. It is therefore essential to focus on prevention. Water management is a key factor in order to prevent this disease. Always make sure your last watering enables the leaf to dry fully before going into the evening, and monitor moisture levels to see if any additional water is needed in the first place.

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