I think this lovely picture of rural Leicestershire sums up September well to me. Misty and murky weather with not a lot of air flow and at times exceptionally humid. This blog is the first one of October and traditionally to me one of our worst disease months that we face as an industry after what would normally be a pretty stable September, but not this year. September 2017 has been exceptionally hard from a disease pressure scenario, particularly in central and southern England.
Let’s see what this month is going to kick off with, maybe we got the worst side of the coin in September and there’s better things to come ? (the eternal optimist in me making a rare appearance there…)
Well when you look at the packed isobars on the Unisys Weather GIF above, I think we can safely assume that weak air flow won’t be an issue for the coming week or so with an Atlantic low pressure firmly rooted over us.
So Monday starts with a real north -south divide in terms of wind strength and rainfall with high bridges over Scotland already subject to delays and heavy rain over Central Scotland. Here in Leicestershire we have a gentle breeze and it’s dry and that’s the way we look to stay across England and Wales with a dry day, moderate to strong breeze and periods of sunshine. That rain over Scotland has already pushed down into the north west of England / North Wales and so a wet start to the week here. Ireland looks to have a largely dry start as well save for some thicker cloud and coastal rain up in Donegal though I expect to see some showers cross The Irish Midlands during the morning and also across the south coast of Munster. As we progress through the morning that rain over Scotland will become confined to western coasts and the same across the north west of England so a drier picture emerges for all for the 2nd part of Monday although that rain will linger over western Scotland. A strong westerly wind in the south will pick up during the morning but it’ll be there from the word go in Scotland with gale force westerly / north westerly winds already present. Temperature-wise it’s mid to high teens depending on your location so pretty typical for this time of year.
Moving onto Tuesday and as that low pressure nudges past the tip of Scotland that means the wind direction will change to more north westerly and so feeling cooler on Tuesday. That air stream will pull cloud in from The Irish Sea so north westerly and westerly areas will have a dull day with potentially cloud thick enough for some drizzle across north west Scotland. Further south and east of this and it’ll be a bright, dry, but chilly day for Wales, England and Ireland with that strong north westerly wind in situ. Temperature-wise I expect low teens for most of us because of the wind direction.
Mid-week already and overnight we see that low push in rain to north west and Central Scotland and this will quickly push southwards into north west England in time for the morning rush hour. A dry start for Ireland, Wales and England but it won’t last as by late morning we see rain pushing into north west Ireland and England and this will soon cross the former to give a wetter, 2nd part of the day. Later in the afternoon that rain will reach Wales, northern England and The Midlands clearing Scotland as it does so. This rain front is westerly focussed so the eastern half of the country may escape the worst effects of it through Wednesday. By late on Wednesday evening the rain is projected to sit over the southern half of the U.K extending all the way down into The South West. Slightly milder temperature-wise as the wind shifts round to the west but it will still be moderate to strong in force.
Onto Thursday and that overnight rain will stubbornly clear the south eastern corner of the U.K by morning rush hour to leave a clear, bright start to the day for many. And that’s the way it is set to stay for nearly all of the U.K and Ireland, save for some heavier bursts of rain across the far north west of Scotland. Later in the day we may see some thicker cloud across Donegal, the north west of England and western Scotland and some of that cloud may be thick enough for some drizzle. Aagin we see another shift round to a north westerly wind so that’ll peg back the temperatures to low to mid-teens teens for most of us.
Closing out the week on Friday and a dull start for many save for The South West and South Wales where you look likely to see some sunshine 🙂 Speaking of thick cloud, Ireland will see a bank of thick cloud push into Kerry in time for the morning rush hour and this cloud and rain will cross the country during the course of the day reaching Leinster by tea time. For the U.K we will see some sunny intervals during Friday but by and large a cloudy, dull and dry day to finish off the week. Later on Friday evening that thick cloud mass and rain will reach western Scotland and western coasts. The winds will still be north westerly but they’ll begin to drop in strength through Friday and that’ll allow temperatures to nudge up into the mid-teens across the south of England, low teens for Ireland, Scotland, Wales and the rest of the U.K.
So how are we looking for the weekend ?
Well I don’t think it’s going to be an exceptional weekend, particularly across Ireland, Wales and the western side of the U.K with thicker cloud and rain showers likely on Saturday and Sunday. It will be very much a west – east split with less cloud and rain and more sunshine across central areas and eastern coasts. It’s possible that Sunday could see more gaps in that cloud cover and therefore more in the way of sun and with lighter winds it will also feel a bit warmer for everyone with mid to high teens likely, so all in all not great, but not a right off.
So next week starts with a bit of a hiatus as high pressure timidly extends a finger of calm after this week’s low pressure and before the arrival of another later next week. So a quieter start to next week especially for Scotland but it won’t be entirely dry with some scuddy showers around coastal areas. Through Tuesday we will see more in the way of rain for Scotland and the north of England and Ireland as a new low pressure starts to sink towards the U.K and that rain will push southwards I think from Wednesday onwards with a risk of more rain, some of it heavy through Thursday and Friday. So an unsettled week next week with some drier weather for the east earlier on in the week before the weather breaks down at the end of the week. Lot’s of blue associated with this low pressure on Unisys so that means cooler as well.
Since it is the first blog of October we can take this opportunity to look back at September and how it played out GDD-wise.
GDD Comparison – Thame Location
So looking at our Thame location we can immediately pick up that September didn’t conform to the norm from a temperature respect and in turn tracked very differently to last year. In 2016 we had a total monthly GDD of 318.5 for September compared to 234.5 for 2017, so in other words we were 26% cooler this year than last in September.
Does that set a precedent for the coming winter in terms of temperature and rainfall ?..No I don’t think it does because when we have had cooler Septembers in the past we have had both cold, dry and mild, wet winters, so no clues yet I’m afraid. (I’d rather not know anyway)
Looking at the y.t.d we are still tracking as the warmest year recorded since we started this exercise but the difference between the last warmest year, 2014, is beginning to decrease. I wonder what I’ll be typing in another months time ?
GDD & Rainfall Comparison – September 2017 – UK Locations
Looking at the graph above we can see that there has some significant variation in both temperature and rainfall across the U.K with the western side of the U.K receiving the bulk of the rainfall and cooler temperatures. When you consider that September is usually a stable, drier weather month with high pressure traditionally dominating then we can see quite clearly how different this September was to the norm.
Looking at the variation in rainfall, we can see that the west has picked up the majority of rainfall with Manchester, Bristol and Okehampton all > 120mm for the month compared to 50 – 80mm being closer to average in central locations. So although the temperature wasn’t great in terms of GDD, many people experienced high growth levels because there was consistent moisture present through the month. That consistent moisture has also been driving another issue and that is disease…more on that later…
GDD & Rainfall Comparison – September 2017 – Irish Locations
Again we can see the effect of the west – east split in terms of rainfall figures with September 2017 going down I guess as one of Ireland’s wettest Septembers ?
GDD-wise, there isn’t much difference between all the locations even from Clairemorris to Dublin but it’s the rainfall that is really striking. Close on 200mm on all the Irish locations, except Dublin. I had to re-check all of this data because the difference was so striking but yet again we can see a huge difference geographically across Ireland as we do across the U.K.
It’s no surprise then that with this combination of temperature and rainfall, disease has been a huge issue across the U.K and Ireland during September 2017.
I’d really point the finger at the moisture part of the above stats as providing the humidity in the atmosphere to give long periods of leaf wetness, a key driver to fungal mycelium growth.
September 2017 – Why was it such a bitch of a month from a disease management perspective ?
So I’ve picked Manchester as my location to analyse for no good reason than it is typical of a western U.K / Irish location in September receiving high levels of rainfall and consequently humidity…
So if we look at the graph above (apart from the obvious lack of dry / drying days) we can see that the dotted blue line stayed above 90% humidity for the entire month and that means the plant was wet most of the time.
It isn’t just a case of being wet overnight and drying in the day though because high humidity in the day means there’s less dry down potential for the leaf because the air is already saturated.
Last week I was spraying some trials and had to swish off 1500m2 of turf nursery before I did the trial (a great way of getting my daily step count up and working those hips 🙂 )
As I was spraying the trial, some 30 minutes later I noticed that the dew was reforming on the leaf.
I noticed this specifically because one of the fungicides I was spraying had an adjuvant package within the formulation that effectively decreased dew formation and the next fungicide I was spraying patently didn’t. (Regardless of the manufacturers blurb claiming this and that…)
The picture above shows the difference between the plots, fungicide 1 (on the left) had no effective dew mitigation compared to fungicide 2 on the right. The picture isn’t really about fungicide adjuvant packages and their performance (though it is interesting to me) it’s more about the fact that the dew had already reformed enough in 30-40 mins after swishing to make the plant leaf wet enough for me to see the difference.
That’s the feature of high humidity we have all experienced in September, re-forming dew after mechanical removal / cutting and that’s been the key driver to disease intensity be it greens, sportsfields or fairways.
We aren’t just talking Microdochium nivale with respect to humidity and being a key driver, Dollar Spot, Leaf Spot and Red Thread all share this feature, so if you’ve seen high activity of these diseases on your outfields during September, then you know why…
Last week was an absolute bruiser in terms of sustained disease pressure, one of the worst I’ve ever known at this time of year and you can see why when you look at the data from my own weather station…
Above you can see long periods of the day (and night) when the air temperature was > 14°C and the humidity was at 100%. On the 25th, 28th and 29th of September in particular.
This combination of conditions allows fungal mycelium to express themselves fully as they look for a new host so this sight below was common on higher-height-of-cut turf last week.
If you look very closely at the top image, you can see droplets on the end of the grass leaf blade, this is guttation fluid, a subject I have covered before and basically this contains sugars and nutrients exuded from pores at the tip of the grass leaf.
It has long been associated with the encouragement of disease formation, I read an article right back from 1968 discussing the presence of guttation fluid and the incidence of Dollar Spot.
In the image below, you can clearly see mycelium of Microdochium nivale growing in the guttation fluid…(circled in red)
Cutting to the chase…
So my final point is this….If you saw mycelium on your turf last week and you’d recently applied an approved fungicide, it doesn’t mean that it hasn’t worked. It means that climatic conditions tipped the balance so firmly in favour of disease development that the fungicide A.I (‘s) is / are / were incapable of holding back the population growth of the pathogen to the point where the disease dies / died out. My other point is that you were not alone, lots of people were in the same boat.
When you see aerial mycelium like this it means the fungal disease is likely to have gone through its complete life cycle and is now looking to move to a new host to infect it and that’s what you can see above, cottony white mycelium growing from one plant to another…
With declining night temperatures this week, high air flow (wind) and some rain I think we will see a big drop in disease pressure, even in the south of England where bar one night this week (Wed), the projected night temperatures are all in single figures, (a big difference from last week), so fingers crossed we will get back to a bit of normality…..
No blog next Monday I’m afraid because I’m taking part in the Troutmasters Final at Draycote Water, near Rugby, so the phone will be turned off and that’ll be me fishing against 100+ professional competitors…This time next week I’ll have done my first 3 hour session on the bank or boat and will have no nails left….seriously though it should be a great experience whatever happens and I’m kind of looking forward to it…
All the best..