It’s been a pretty bleak year in 2024, it seems like it’s only just stopped raining and we see a wild flush of disease pressure.
Why is disease pressure worse this year than last?
Like all fungal turf diseases Microdochium is really driven on turf by temperature and moisture.
Temperature
On the temperature front, few of us have seen any usefully cold weather (sub 2°C stopping hours).
As you can see in the blue line in the graph below most have spent a fair bit of time in the peak of that Microdochium bell curve (7-13°C).
The diseases happy place, where turf growth is slower and it can really take hold.
I’d say the temperature part of the equation is quite easy.
When we (the Turf Advisor app) says ‘temperature’ we mean average daily temperature.
So a whole day, every hour being 8°C would have that as the daily average.
Or a day where 12 hours were 4°C and 12 hours at 12°C would also be 8°C daily average.
– A million other number combinations, but you get the point…
It’s an easier way of looking at days to look for patterns, other metrics like ‘day time high temperature’ or ‘night time low temperature’ only give a snap shot.
It’s not perfect but daily average gives a more representative value.
As you can see below, consistently in the danger zone temperature wise.
The problem with the temperature part of the equation is we spend a lot of the season in this zone, so it’s not the best for narrowing times of disease threat down.
We can’t be on high alert for 6 months of the year…
Moisture
The other half of the equation for fungal disease pressure is moisture.
Comes in many forms:
- Dew
- Mist
- Fog
- Humidity
- Rain
- Irrigation
- Snow cover
- Guttation fluid
The Greencast Microdochium model was developed with the STRI over a decade ago, and the moisture data they used in the model is rainfall.
You need 3 rainfall events in a 6 day period to get disease pressure in the current model.
As we’ve not seen any rain recently the model says “0” – yet we are seeing high levels of disease outbreak currently.
Glenn and I recorded a video last year to run through how the model works and why it’s not perfect… (Especially in periods without rainfall). Watch it here.
Last season we had lots of rain at this time, meaning the model performed better, but more importantly rain does have a direct spore “knockdown effect”, meaning we see less disease directly after rain.
Diseases also don’t like waterlogged surfaces, like me and you they need oxygen to operate.
Like with all things I mention in the blog there is a ‘Goldilocks zone’.
The turf surface remaining wet for long periods of time is a real disease driver.
If we were to push Microdochium patch disease in a lab setting, we would set the temperature low enough to slow the turf and keep gently misting the turf canopy, keeping humidity high.
Leaf wetness is the enemy here, so our best friends (outside of cultural activities like dewing off) would be sun shine and wind to clear that moisture build up off the turf surface.
You can see below we’ve had very little air movement, and sunshine hours have been virtually non existent in the first third of November.
One positive of disease outbreaks is good pressure in trials (but that’s really personal to me, no one else see’s the positive).
The STRI in Yorkshire, UK are running several trials for Syngenta this season.
Liam who is conducting some of the trials for us sent me these photo’s this morning:
This is not to say any one product is a magic bullet.
Instrata Elite is a powerful tool for the control of turf disease, BUT like everything it has limits.
After a certain amount of time (10-14 days on average in high GP conditions) if a strong wave of disease pressure breaks on you, you will see outbreaks.
Fungicides are tested to achieve +90% disease control. So you may have made the perfect application 8 days ago and still see some disease if conditions are highly conducive to development.
The important thing here is to imagine you could have 9 more patches of disease for every one you see on your surface, if you hadn’t sprayed.
Make sure you are doing everything you can in the cultural practice space to support the activity of fungicides: ITM – Integrated Turf Management is key.
Model revamp
Glenn is working with the global digital team in Syngenta to get a better model to track the disease which will be a welcome addition!
Tips on setting up your prefect dashboard in Turf Advisor with Microdochium in mind – look no further!
Until we get that upgraded model it’s going to remain important to monitor humidity & rainfall, along with temperatures here.
For those who already read and gleamed some insights from the dollar spot state of the nation survey, the Microdochium version is undergoing it’s final edits now…
So watch this space to see how fellow turf managers are tackling disease threats throughout the land.
Syngenta are taking some Microdochium samples this season in the UK, and throughout Europe, to assess the sensitivity of different strains of turf disease to the available fungicides.
Which is important for managing our fungicide rotations when building programs.
We’ve got a few other blogs on ‘the old enemy’ which I think after last years low pressure year everyone was hoping we wouldn’t be needing, so do check those out for further tips on getting a handle on an outbreak.
