Dollar spot trial update

It's been an absolutely amazing summer so far... for Dollar Spot. It doesn't mind it warm and wet one bit, in fact it prefers that to hot and dry as it needs moisture to thrive and spread.

Dollar Spot Trials in the UK

I did a blog at the start of July about Dollar Spot (click here to read that) and since it’s our ‘Disease of the Year 2023’, and I’ve got a few user trials going on to look at it, I’ll have a few more coming as the results come in.

It’s not because its the worst turf disease for most sites (although it is becoming that for some) but because its a disease we’ve historically not had such problems with, and so could fairly safely ignore.

My colleague Baptiste, who’s the French me in Syngenta (except with a moustache) insists that Dollar Spot is the biggest disease pressure course managers across the water face.

They sit that bit warmer than we do so that’s to be expected, but the prospect of a warming climate does ask the question.

One of this years Dollar Spot user trials has been running since the end of June. With assessments of % disease cover carried out once a week.

The set up is simple, half of each Tee is treated the other half not.

We assess the disease cover for each side, and also for a quadrant (like in the top photo) in each side.


As expected with so much rainfall in July we’ve seen quite high Dollar Spot pressure.



30% doesn’t sound like a lot but that’s a third of that area visibly damaged by disease, which is going to be noticeable to golfers.

Also worth bearing in mind that its an average across all the Tees in the trial, so some are above 70% area damage and others lower, to even that out.


Some learning points so far:

  • We can recover from Dollar Spot damage. You can see from the 21st July the untreated area drops where we have dropped out of high disease pressure and had the conditions to grow out damaged turf.
  • We can manage high disease pressure with well timed fungicide applications.



Speaking to Glenn about this last week, the ‘action threshold’ for each site to need to treat, if following the Smith-Kerns model, is going to vary.

Depending on a number of factors, including:

  • Player expectation – can you get away with a level of disease?
  • Cultural practices – what are you doing to reduce the Dollar Spot pressure?
  • Grass species composition – susceptibility of your sward


In the trial we set the action threshold at 20%.

So when the Turf Advisor app reaches 20% disease pressure the sites need to apply a fungicide and that gives a break of 25 days. Then you need to start monitoring pressure again and apply once it reaches 20%.

If your site can afford a little Dollar Spot without issue you would set the threshold in the app higher say 25%.

If any damage is too much damage, then you could set that lower, say 17%.

The same would be true for cultural practices and grass species composition.

These would mean you crank it up or drop it down accordingly.

Recent work in the US for example suggests that the difference in susceptibility, just in the bent grass camp alone is huge.

As Dollar Spot pressure low as 14% can cause disease on some cultivars and others will be looking fine all the way up to 28%.

What you want to define is the pressure at which your site sees disease, so you can take action before that point.

So if you see unacceptable disease outbreaks at 25%, according to Smith-Kerns, you might set the threshold at 22%.

We want to start figuring this out now, before the climate means wide spread Dollar Spot damage like they are seeing in some areas of France.

I’ll keep the updates coming in this year of the Dollar Spot and hopefully we can see some more insights.

Thanks for reading!

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