June 7th

Hi All,

Well a week of sunshine and some very heavy rain for the south east and east has resulted in huge amounts of growth and not a small amount of disease.

Some beautiful evenings as well with cracking sunsets and cloud formations but don’t worry I won’t be featuring Mammatus clouds in this week’s blog 🙂

On the subject of beautiful evenings, I love this time of year not least because you can fly fish up to 10 p.m. and chase some lovely Trout on a dry fly.

At bit self-indulgent I know but here’s me connected to one of Eyebrook’s reservoirs finest on a cracking evening last week….

This week coming up looks alot more settled with some heat building at the end just in time for the weekend but for most areas the drier weather it should allow you to get surfaces back under control. Beautiful weather at the moment but we must always remember June can be a fickle month. Many a year have we endured a cool and wet middle of the month interlude so let’s see how things are shaping up.

General Weather Situation

So we start the week with low pressure out in The Atlantic and high pressure over most of the U.K. There’s a rain front just off the west coast of Ireland but it doesn’t look to make much progress and other than to push some cloud cover into Ireland today, it should be reasonably dry here. For the U.K, we have some pretty humid air around courtesy of that low pressure feeding moisture into the weather scenario. After a dry start this is expected to trigger off some showers primarily for the eastern half of England and these will intensify as we go through the afternoon into the evening. Predicting exactly where and when is a job for rain radar so best to keep your eye on that. So a dry day for the west of the U.K and Ireland with pleasant spells of sunshine and temperatures in the low twenties. This evening that rain front will eventually push into the south west of Ireland whilst the showers across the east of the U.K fizzle out. So high teens for Ireland and the west of the U.K under that cloud cover whilst the south of England may see temperatures up into the low twenties. The wind will be light and from the south west.

Onto Tuesday and that Atlantic low pressure fails to make progress eastwards buffered by high pressure over the continent. So the west of Ireland will see some rain as will the north west of Scotland but other than that, a fine, dry day for England, Wales and the majority of Scotland. Later in the afternoon that rain pushes into the west and north west of Ireland. Similar temperatures to Monday with high teens across Ireland and Scotland courtesy of that thicker cloud cover up to low twenties for Wales and England. The wind remains in the south west and will be light to moderate, stronger across the west.

Mid-week already and Wednesday sees that rain across the west of Ireland make inroads both north and east overnight so showers pushing into the Irish Midlands early doors on Wednesday. Scotland will see rain across the west and north west initially but through the first part of the morning those showers will cross Ireland into Scotland and the north west of England. Further south and east you look to enjoy a sunny start with pleasant temperatures. As we go into the afternoon, Ireland looks to dry up as those showers push eastwards whereas the rain over Scotland will push into central and western areas. Further south for England and Wales, another fine and dry day with lots of sunshine and temperatures building towards the mid-twenties.

Thursday starts pretty dull for all areas except eastern coasts/ East Anglia. That low pressure out in The Atlantic off Ireland is still having its say on the weather and it’ll push in some showers to Kerry along with some pretty thick cloud. During the afternoon that thick cloud retreats westwards so more in the way of sunshine for the 2nd part of the day but Ireland, Wales and the west of Scotland will remain cloudy with some isolated showers across North Wales. For Thursday evening we will see some showers continuing across the south and north west coasts of Ireland and across the north west of Scotland. A real west-east split with mid to high teens across the west of Ireland vs. low twenties for the east. For the U.K, low to mid-twenties again.

Closing out the week on Friday we see another largely dry day save for some isolated showers across North Wales and The North West. Again plenty of cloud for Ireland and the western half of the U.K with the sun breaking through across central and eastern areas during Friday morning. High pressure is now in charge so the wind shifts round to the north west and that’ll just cool things down a tad but still low to mid-twenties. Dry across Ireland and Scotland as well but plenty of thick cloud for the latter will make it a dull one after early showers fizzle out across the west and central areas of Scotland.

The outlook for the weekend looks fine and dandy with very similar weather to the preceding days. Plenty of sunshine through Saturday and Sunday after early cloud burns off. Still duller across Ireland and the west with the threat of some showers pushing into the west coast of Ireland and Scotland later on Sunday evening. Low to mid-twenties again, ho hum,

Weather Outlook

So as you can see we start next week with a finger of heat from that southern Europe high pressure pushing across the U.K & Ireland so a fine and dry start to next week but it isn’t set to last according to the predictions as low pressure pushes it aside and begins to introduce rain for the north and west through Monday. Now to me this is finely-balanced as it was for this week. I think you could easily see the high pressure continue to dominate but heh what do I know 🙂

So if we follow the GFS projections it looks like we see rain push in through Tuesday and Wednesday across Ireland and the southern half of the U.K and introduce cooler air for the rest of the week. By the end of the week the rain should have cleared through just in time for me to start my weeks holiday 🙂 . Looking at the ECMWF, they have the weather breaking down a bit later in the week and the low pressure more northerly than southerly-orientated so I think we can conclude that there’s a fair bit of uncertainty about next week’s weather !

Agronomic Notes

So in this week’s blog we will take a look back at May 2021 and see how it shaped up across the U.K & Ireland and also discuss whether last week and this week’s weather constituted an Anthracnose trigger.

GDD – May 2021 – Thame location

So as intimated last week, May 2021 will go down as a cool one, in fact the 2nd coolest since I started looking at GDD stats over 10 years ago. You can see just how different it was to last May !

Well if you look at the cumulative GDD total till the end of May and compare it with other years you can see just how far behind we are in reality. The total GDD at the end of May 2021 came in at 271.5 vs. 277.5 for the end of March in 2020, so we were about a month behind normal. We are only just ahead of 2013, that long drawn out winter when we still had snow in the hedgerows in mid-April. Comparing with last year, in 2021 till the end of May we had 45% less GDD than to the same point in 2020. We are though now playing catch up with a vengeance !

G.P and Rainfall Summary – May 2021 – U.K Locations

Well these figures tell a story in that not only was May 2021 a cool month but it was also very wet with most areas receiving close to 100 mm of rainfall for the month. The wettest area by far was The South West with 219.1 mm of rain recorded (you have my sympathies Pete 🙁 ). Growth was obviously disappointing when you consider that the total monthly Growth Potential figures are out of a possible 31 (31 days in May x 1.0 optimum growth) with most areas showing 42% of optimal growth for the month. Scotland (Fife in this case) showed how the eastern side faced a cool and wet month with only 28.5% of optimum growth so a slow start here. My location was the driest because…….the rain went around me 🙂

G.P and Rainfall Summary – May 2021 – Irish Locations

With the predominant weather systems for May being Atlantic low pressure systems, it should come as no surprise that Ireland was on average wetter and cooler than the U.K locations, though not by a great deal. Growth potential-wise, the average for Ireland was around 33% of optimum so a slow growth month for sure and of course with lots of rainfall for the south and west of the country, it made life tricky in many ways.

Disease Pressure

What both of these charts don’t show is the prolonged disease pressure that remained a constant issue through May 2021 with the combination of heavy dews, extended periods of leaf wetness and some mild nights courtesy of cloud cover. For Ireland this picture has continued into June and remains an issue no only for Microdochium, but also Red Thread and I expect, Leaf Spot.

Anthracnose Trigger

No we know that this disease is both an interesting and a destructive one for the summer and sometimes the autumn as well in the U.K & Ireland. We also know that it requires a combination of air temperature and less wetness / relative humidity. Indeed as early as 1984 Karl Danneberger, Joe Vargas and A.L.Jones produced one of the first turfgrass disease prediction models for this disease based on air temperature, period of leaf wetness, etc to try and predict its behaviour and potential infection severity. Leaf wetness is key for Anthracnose because it needs a wet leaf for the fungus to develop into the 1st phase of the disease during which time it enters the epidermis and then sits in a resting – Biotrophic state waiting for a stress-related trigger.

It is interesting talking about disease prediction models because I noted the Smith Kerns model also showed a rapid increase over the last week and that works on air temperature and humidity ;

Smith Kerns output – 2021 y.t.d – Great Dunmow, U.K

Over a number of years we have seen periods of 25°C air temperature but no subsequent Anthracnose following on from this and for me this is because we haven’t had the required leaf wetness and / or the plant-related stress that require development of the initial biotrophic and subsequent necrotrophic states. Plant leaf wetness is as important as the trigger air temperature so looking at the last week we have seen some high air temperatures followed in some geographical areas by rainfall and therefore high humidity and plant leaf wetness. This has mainly be confined to the east and south east of the country which ‘enjoyed’ some significant downpours at the end of last week punctuated in-between by high air temperatures and E.T.

Here’s some stats from our Great Dunmow Davis Vantage Pro 2 Weather Station for June 2021….

Monthly stats – June 2021 y.t.d – Great Dunmow, U.K

So in this location they had 1 day of very heavy rain, some bruisingly high E.T at close to or over 6 mm on the first two days of the month and some high humidity as well.

Here’s how it looked on an hourly basis through that period ;

Air temperature, plant leaf wetness and relative humidity – June 2021 y.t.d – Great Dunmow, U.K

So interpreting the graph we see ;

  1. Trigger temperature in terms of air temperature was reached early on in June and we must also remember that the surface organic matter temperature where the spores reside was likely higher.
  2. Following the high air temperature days we saw long periods of high humidity caused by the heavy downpours on the 4th of the month.
  3. During the 4th, 5th and 6th of June we saw extended periods of plant leaf wetness with a period on the 4th – 5th June that lasted nearly 24 hours

So my hunch would be that in areas that got rainfall on the 4th, 5th and 6th of June it is likely that you experienced an Anthracnose trigger event provided your air temperatures were similar to those above.

Doing a quick hop skip and a jump on the Netatmo weather map and looking at some of the monthly stats I’d say that the west of the U.K has had the temperatures but not the rainfall thereafter (in general). For Ireland, the temperature and rainfall trigger points haven’t quite been there for the east and south east of Ireland. For Central Scotland, you look to have had both the air temperature and rainfall triggers to me. So my money is on Scotland, The Midlands, East Anglia and South East / South of England as ticking the Anthracnose trigger boxes and of course if we have continued heat this week and if we do get a low pressure breakdown next week, we could see this extend the trigger period. We will of course need the follow up stress period to transform the biotrophic trigger into actual Anthracnose symptoms, Watch this space….

We have covered BMP for Anthracnose before and there’s plenty of info on the web from Bruce Clarke at Rutgers State in terms of up to date advice but I’ll leave you with one salient point and that’s plant N levels from their work. The graph below shows plant tissue level in terms of nitrogen on the bottom axis plotted against Anthracnose %. You’ll see how the % Anthracnose is much higher at low N levels and then it drops markedly when the plant N tissue level reaches 3.6% which is adequate but not excessive N for either Poa annua or Bentgrass. So keep your greens healthy from an N perspective which means happy but not under or over-fed. 3.6% N for me in a tissue analysis would be a nice consistent N level and would not represent excessive growth.

Image courtesy of Bruce Clarke – Rutgers University

OK that’s me done for another week, I just missed the 13:00 publishing slot dag nabbit…

All the best for the coming week.

Mark Hunt