It's a tricky time of year to manage disease right now and true to form there's a lot of disease pressure floating about.
The biggest problem I see is that turf managers hope or believe that small amount of a disease will grow out because they are still getting some growth.
Preventative fungicide applications are always more effective than curative but deciding when you start is tricky. No one wants to waste fungicide but we're all aware that if disease (particularly Microdochium) really gets hold and the Winter stays mild - which is the increasing trend, then getting control of it means more fungicide applications not less.
These early stages of Microdochium don't just appear overnight, yes they can appear to the eye quickly but they've taken a few days to get there. I like to look at GDD as an indicator for the problem period. If daily GDD is floating around 6 then it's highly likely that you'll be entering into a period that suits disease development.
Check out the GDD calculator here.....
It's not that GDD is some magic formula but it does indicate temperature ranges. For a GDD figure of 6 you need to be floating between 9 to 15 degrees which is a pretty good temperature range for Microdochium to get a hold. It's also a period of the year that we're unlikely to move back into strong growth as light is constantly reducing.
If it floats around 6 figure for 10 days which it has on the two sites that sent me these images then that disease was ramping up daily just waiting for the right break in the moisture levels to explode.
So what's my advice if you're in this situation? Get a Contact / Systemic fungicide down ASAP. Instrata Elite is my go to product at this time of the year.
Yes it would have been better as a preventative but if you've missed that boat don't wait even longer.
It may have been more effective to apply yesterday but if you apply today it'll be more effective than tomorrow.