9th September

Hi All,

First up my apologies on the lack of blog last week. I am afraid this will be a pattern from now on as other matters take precedence. I will do my utmost to keep some form of consistency especially as we move from summer to autumn and Microdochium nivale rears its inevitable head.

In the flash of an eye seemingly we have moved away from summer to early autumn, with the nights drawing in fast, the harvest completed and some chilly mornings not far short of a frost lately. Sunday morning we were down to 2.2°C. We will though I think enjoy an Indian Summer this September so don’t put away those shorts and sun cream just yet eh…

Sept 15th, 2019 projected jet stream path – www.Tropicaltidbits.com

I was reading in New Scientist the other day about some suggested schemes to re-ice the Arctic in the hope of avoiding the climatic Armageddon that is currently heading our way. One part of the article looked at why losing ice from The Arctic is so bad and of course one immediately thinks of rising sea levels and the risk of more coastal flooding. One of the other points made was a growing weight of evidence that the warming Arctic is affecting the behaviour of the sub-polar jet stream, the one that gives the U.K and Ireland its ‘particular climate’.

The article explained that with less temperature difference between the Equator and The North Pole, there appears to be less energy driving the jet stream and so it forms into the meanders (Rossby Waves) that I’ve been talking about for the past 10 years or so.

The best way to think about this is looking at a river from a bridge. In mid-current the flow rate is strong and straight with very few meanders but as you come to the side where the bank shape affects the flow, you’ll see a slower flow rate and meanders / eddies in the current. This week coming we see a ‘peak’ pattern forming in the jet stream where its flow is slowing down and warm air is pushing up from Africa.

Did this happen 100 years ago ?, who knows ? because we’ve only known about the existence of the jet stream since the mid 1940’s and to this day we understand very little about the complex mechanics that creates its pattern and speed. Ultimately this is why we cannot predict the weather further than 10 days away so please don’t ask me how winter 2019 looks 🙂

General Weather Situation

Sitting at my desk on a drab, grey Monday morning, it looks far from an Indian Summer outside and on the rain radar bands of rain that crossed Ireland overnight are now orientated vertically across the U.K and slowly moving eastwards. So if you are dry, you may not stay that way for long. There’s some particularly heavy rain crossing Wales currently and that bring flooding to some areas. So Monday looks a wet one for the U.K but across The Irish Sea you look better with just some showers pushing in off the west coast likely this morning. This rain is slow-moving and so expect showers and thick cloud for most of the day only clearing in central and eastern areas later this afternoon with a likelihood of the rain persisting across the south coast, The South West and Wales till dusk. On the cool side as well with only 14°C likely under that thick cloud and rain. despite a southerly orientated wind.

Onto Tuesday and the rain has cleared overnight to present a largely dry picture, dull as well but low pressure isn’t finished with us yet as another pushes in from The Atlantic. Now the projections are for it to sit out off Connacht tomorrow morning so the U.K and Ireland look to have a dry morning / afternoon but as we approach the late afternoon, the rain makes landfall in north-western Ireland and pushes across country. So dry with some cloud cover breaking across the U.K through Tuesday morning, staying cloudy across Ireland and Scotland with rain pushing into north-west Ireland late afternoon Tuesday. During the course of Tuesday evening that rain pushes across Ireland and into north-west / west Scotland with some heavy rain bursts for the north-west of Scotland. In the wee hours it’ll be across Ireland, Scotland and pushing down into North Wales and northern England. Despite the threat of rain on Tuesday for Ireland, the U.K will enjoy a warmer day with temperatures pushing up into the high teens with some hazy sunshine and cloud. Winds will be light and from the north swinging southerly later.

So by dawn on Wednesday that rain has cleared Ireland save for some showers over the tip of Kerry. It’ll be spread in a line down the western half of the U.K, across northern England, The Midlands, Wales and The South West. So East Anglia and The South East will enjoy a dry start to Wednesday but it probably won’t last. So through the course of Wednesday morning that rain will move south and east clearing Scotland and the north / west of England as it does so. Expect there to be some showers over north-west Scotland throughout the day. Ireland with that rain long gone should enjoy a largely dry day with temperatures picking up a bit from their recent low’s to mid-high teens. Warm in the south of England as well in-between that rain with temperatures sitting in the high teens.

Onto Thursday and a north-south divide presents itself with rain pushing over the north and west of Ireland through Thursday morning with the south staying mainly dry. That rain will soon be into the north-west of England, Western Scotland and during the morning will push eastwards across Central Scotland. So for southern and central areas of the U.K, Wednesday should be dry and getting warmer as high pressure nudges up from the south. Temperatures should be in the low twenties I think for these areas with Ireland in the high teens away from that rain and mid-teens for north and west Ireland and Scotland. So a wet day for north and west Ireland but as that rain pushes eastwards, the sun follows it and temperatures pick up nicely for the 2nd half of the day. Windier on Thursday though with a strong south-westerly – westerly wind coming to play.

Closing out the week on Friday and high pressure is very much in charge with clam and settled conditions over U.K and Ireland. A much milder night will give way to long spells of sunshine and temperatures picking up into the low twenties for England and Wales. Ireland and Scotland will be a bit cloudier and that’ll keep the temperature down in the mid-high teens but crucially dry. Winds will be light and from the north.

With high pressure asserting itself and pushing warm air northwards the weekend looks to be fine, dry and settled with plenty of sunshine, light winds and temperatures up in the high teens / low twenties. Just as well then as I’m off for a week 🙂

Weather Outlook

So will The Indian Summer remain in place for next week ?

Well the short and sweet answer is yes, next week looks like high pressure calls the shots so that means cool nights, heavy dews, warm days and plenty of sunshine. I expect day time temperatures around 20°C for England and Wales and 18-20°C for Ireland and Scotland. By the end of next week the high pressure looks to be pushed eastwards by a north-west Atlantic low pressure so we could see things break down from the end of next week.

Agronomic Notes

Since this is my first blog of September, we will of course have a look back at the previous month and see how the land lies. Very much a north-west – south-east divide though, especially when it comes to rainfall with some areas very dry for the month, others excessively wet.

GDD Summary – August 2019 – Location – Thame, Oxfordshire, UK

Interestingly, August 2019 came out almost identical to August 2018 when it comes to GDD and ranks as one of the warmest August months for this location. When you look back at the previous years figures you see remarkable consistency in the total GDD value on the hotter Augusts. 2013 came in at 360.5, 2016 at 364.5 (identical to 2019), 2018 at 362 and 2019 at 364.5. 3 of the last 5 years have come in with a very hot August from a temperature perspective at this location. I know that it will be very different at more western and northern locations. Remember I said 2019 was tracking in a very similar fashion to 2016 a few months back ?, well there’s your proof.

Overall for the y.t.d, GDD-wise we are tracking behind 2018 and 2017 courtesy of that much cooler (and wetter) June we endured this year. That period of weather has had consequences from an agronomic perspective, some of them good, some of them bad.

G.P / Rainfall Stats – U.K Locations – August 2019

During August we saw a north-west vs. south-east divide across both the U.K and as you’ll see shortly, Ireland. The main rain fronts affected the north and west of the country and so these areas ‘enjoyed’ a cooler, wetter August vs. south and east where it was both warmer and drier. The Bristol and Fife locations back this up with ≈ 150mm of rain for the month. Growth-wise as measured by G.P there’s similar variability with the wetter locations lower as expected.

Looking at the Irish locations we can see similar variability albeit much wetter than the west and north of the U.K. So the west and north-west side of Ireland endured a very wet August with over 8″ (200mm) whereas the east side was 45-50% lower from a rainfall perspective. GDD-wise, any month when you’re recording > 250GDD means if you had rainfall, you also had significant growth. Donabate, north of Dublin came out with the highest GDD figure and 164.6mm of rain so I imagine keeping on top of growth there was tricky in August.

I find it sometimes difficult when you look at the variability between locations in the U.K and Ireland to write a ‘one-size fits all’ sort of blog because on one hand you have a very wet and cool August vs. a warm and pretty dry one elsewhere. Some courses will be more concerned about flooding whereas others will be experiencing a continuation of our dry (ish) summer. Looking back at last August I can see a similar picture with drier conditions across central and eastern areas and much wetter conditions across the north and west.

Disease Activity – Take All

Late summer this year has shown a high level of Take-All activity on a lot of surfaces and not just affecting Bentgrass either. I’ve seen it on greens, collars, approaches and tees and it’s been taking out Bent and Poa annua. as well. No why should this be ?

Well to answer that question we have to go back a few months and look at June 2019’s weather pattern.

Looking at the very nice chart created as part of the 2019 GDD / G.P spreadsheet, you can see a pronounced dip in the early part of June from a G.P perspective and that’s because it was cool. We also see some pretty heavy rainfall lasting for 7-10 days. It was this climate dynamic that has led to increased Take All activity this summer.

Take All as a pathogen is usually active in a cool, wet spring, typically between March and April, attacking the root system of its chosen host plant. Symptoms however do not show until the plant goes under E.T stress during the heat of summer when it needs to uptake more moisture through its roots. The damaged root system is unable to uptake sufficient moisture to replace that lost by E.T and so the grass plant shows symptoms of wilting and die-back in a characteristic ring-like pattern. The above scenario is normally only an issue on new constructions in their early years and typically it is a Bentgrass-only pathogen.

When we have a wet summer though this cycle seems to repeat itself and so with the cool and wet June period of weather I think the pathogen was active on Poa and Bentgrass roots, but symptoms didn’t show until we experienced some drier, warmer weather during late July and August (depending on your location)

So if you’ve seen some die back in rings this summer, it is likely to be Take-All disease and for myself, other than rubbing in some chitted seed and rootzone into the patches, I think you’ll see it grow out under favourable agronomic conditions.

Microdochium nivale

I am wondering looking at the stats for the north and west whether those locations saw increased Microdochium nivale activity during August with the long periods of plant leaf wetness and mild temperatures. For sure as we approach mid-September our thoughts turn to controlling this pathogen and the two hard previous autumn conditions we have endured.

This autumn I am guessing most of you will have stock of Propiconazole-based formulations if you purchased before June’s revocation date and so in terms of control products will be in a similar position to 2018.

It’s not until next autumn that we move into a position of relying on fewer chemistries with (hopefully) some newer ones as well. Some of you out there I know will be trying to control this pathogen without applying a fungicide instead relying on a good non-pesticidal IPM regime, so by the time we get to spring 2020, it’ll be an interesting exercise to reflect on the weather patterns and disease activity that we experienced and how effectively you controlled it.

Certainly autumn / winter 2018/19 taught me two key lessons ;

  1. Getting to Christmas with a clean sward doesn’t mean you’re over the hump of Microdochium nivale activity
  2. Plant leaf wetness plays a significant role in the development of this disease and perhaps is more significant than just air temperature alone.

Ok that’s the blog for this week, next week I am having some time off so I’ll catch up with you all on the 23rd September.

All the best.

Mark Hunt