May 10th, 2021

Hi All,

Well after a pretty wet Saturday for everyone we saw the wind shift round to the south west and some long overdue warmth wing its way across the U.K & Ireland. Together with a good dollop of rain and temperatures in the high teens on Sunday, you could almost see the verges and grass growing wherever you looked. There’s something so fresh and vibrant about May even though this year we were so far behind. With that change in wind direction comes milder nights, cloud cover and an end to the long run of frosts we have endured so that means warmer nights, milder days and some decent growth in prospect for the week ahead. So with this growth comes some agronomic challenges, a good bit of Microdochium kicking around and some significant incremental GDD.

The weekend’s low pressure system left with a sting in its tale for eastern and south eastern England with 91mm of rain reported from the North Kent coast (thanks Ready) over the weekend with 48mm of that falling on Sunday night !

GFS Output – 10/05/21 – Tropical Tidbits

General Weather Situation

So when you look at the GFS output above it should be no surprise that we are in for an unsettled week as an Atlantic low pressure sits just off the coast of Co. Sligo. So Monday sees showers already forming across the south western regions of Ireland and England and these will be ushered up on a moderate to brisk south westerly wind through the course of the day. So it’s sunshine and showers for us all. These showers will soon consolidate into longer spells of rain across all areas as we go through the day so maybe more rain than sun today. As we go through to late afternoon, that rain clears the southern half of England, Wales and Ireland to leave a reasonably nice end to the day, maybe duller over Ireland though. So a pleasant evening in the south as that rain moves through. Temperature-wise well we should see mid-teens for most areas so 13-15°C with a brisk south westerly wind.

Tuesday sees a very similar pattern with a reasonably dry start after a milder night and then rain moving into the south west of England and Wales and then pushing north and east into central areas by lunchtime. Ireland will see less of the rain, maybe some heavy showers skirting along the southern coast of West Cork, Cork and into Wexford / Leinster later. During the afternoon, that rain again consolidates over the southern half of the U.K before moving off later in the afternoon to give sunny intervals behind it. Scotland will enjoy a pretty dry way with some pleasant sunshine and much less in the way of showers. Similar temperatures and wind direction / strength compared to Monday.

Wednesday sees the centre of that low pressure across The Irish Sea so that means a continuation of the unsettled sunshine and showers we have experienced earlier in the week. So a reasonably dry start but showers will push into Wales, The South West and the the west / south of Ireland first off and then move inland. During the morning we will see that rain push across Ireland and showers / rain develop all along the west coastline of the U.K with Scotland also seeing rain across the north east and west consolidating across central areas through the morning. By the afternoon, that rain becomes heavier across the south west of England and along the coast into West Wales, in fact all of the western half of the U.K. Away from this, central and eastern areas will enjoy a sunny day with just the odd shower pushing forth during the afternoon. Again mild and breezy from the south west with 13-15°C forecast. Ireland and Scotland under that heavier rain will be down a couple of degrees on that.

Onto Thursday and a very similar theme to the first part of the week. So dry and sunny initially save for some showers across central regions before rain bubbles up from the west through the morning and covers much of Ireland and the U.K, with the west more in the firing line again. By late afternoon that rain begins to dissipate and we see some sunnier intervals between the showers. Through the day the wind will change direction to easterly across Scotland, westerly veering northerly across England, Wales and Ireland. This will edge temperatures down a little into the early teens though winds should be lighter on Thursday.

Closing out an unsettled week we start Friday dull with light northerly winds in situ and the odd shower across central England. As we progress through the morning we see some heavier rain across Kent and Sussex and that cloud cover remain before the rain front pushes northwards into Wales with the odd shower across the south east of Ireland and west of Scotland. By the afternoon then we see some breaks in the cloud and the sun breaking through in places but the south east looks to be sitting under that rain with just the odd shower further north and west and across Ireland. The wind is now north westerly and picks up through the day to give a slight chill to events and keep those temperatures down in the early teens similar to Thursday.

So how do we look for the weekend ?

Well Saturday will see a rain front push in from The Atlantic across Ireland giving a sunshine and showers day across the west and central areas though eastern counties may miss it completely. It’ll be a bit on the dull side though. For England and Wales we have a quiet start with plenty of cloud cover, dull with just the odd sunny interval across the east of England. Through the morning we might see the odd shower push inland but overall a dry (ish) day for the U.K, on the dull side with the odd sunny interval. Winds will be moderate and from the north west. Temperature-wise, 13°C appears the norm for this week. Sunday looks a wetter affair with that rain moving across Ireland overnight and into The South West and Wales. By lunchtime it’s across most of the U.K, except the north east of Scotland which may be sunnier for a time. Ireland should clear from the west through the 2nd half of the day. Those showers should also clear England through the afternoon but expect more rainfall for the west. The winds will shift round to the south on Sunday so that means milder air and warmer temperatures pushing up into the mid-teens.

GFS Projected Output – 17/05/21 – Tropical Tidbits

Weather Outlook

So we can see from the GIF above that next week looks to start on the quiet side with low pressure still sitting over us. If you look at the demarcation line between warm weather and cooler weather, it is currently sitting over northern Spain so that means that’s pretty much where the jet stream is orientated. So whilst it’s still low we have an open door for Atlantic low pressure systems to push in and that’s exactly what we will see next week. A sunshine and showers scenario continuing with plenty of rain as well pushing across Ireland and the U.K next week as an Atlantic low pushes across Tuesday and Wednesday on a moderate to strong south westerly wind. For the 2nd half of the week the wind turns round to the north west, so a little chillier before flipping round again as a new deep low pressure pushes in over Ireland, the northern half of England and Scotland at the end of next week with gale force winds accompanying it. A bit Mystic Meg after that, but there is a suggestion the end of May could go warm and settled with some decent temperatures.

Agronomic Notes

So as commented above, quite a change around over the weekend as we saw rainfall for the first time in 30 + days on our Essex site combined with warmer day and night temperatures. You can see the transition clearly in the graph below with the minimum and maximum temperatures over the last week vs. relative humidity which took a hike upwards as moist air arrived.

Air temperature vs. relative humidity – Great Dunmow, Essex

This upturn in day and night temperatures caused an equivalent upturn in growth as we would expect, grass growth and pathogen growth as I’ll come onto later.

You can see it in the daily growth potential (actual and projected for this coming week) in the graph below ;

Daily Growth Potential – Great Dunmow, Essex

So we have good growth characteristics now and for the week ahead which is a blessing and will allow surfaces to come on and areas that don’t receive irrigation to finally begin to grow and fill in.

Poa annua seedheads

From a GDD perspective we have and will pile on GDD this week with the weekend’s temperatures and the mild day and night temperatures projected for the next week so this and the arrival of rain will put Poa annua very firmly into seedhead mode.

You can see this from the graph below when we look at cumulative GDD for 2021 using a 6°C base temperature.

Cumulative GDD 2021 – The Oxfordshire, Thame, U.K

The graph shows the steep rate of ascent of the GDD from Saturday 8th May and how it is projected to reach the point where we know from past experience, the perennial biotype of Poa annua starts seeding around the 12th of May (Wednesday this week). Now of course your Poa biotype might be different, we know it is an adaptive plant species so it’s important to make note of this on your site to build up a picture of how it behaves and then have your cultural work ready 🙂


Disease pressure           Top Graph – Kanturk, Ireland      Bottom Graph – Bracknell, England

Spring Microdochium nivale

Microdochium nivale

As you have probably discovered whether you are in the U.K or Ireland, grass isn’t the only thing that started growing over the weekend !

The increase in humidity shown earlier coupled with mild night and day time temperatures has pushed latent Microdochium into overdrive mode so there’s a lot of activity currently. Looking at the top graph for Kanturk, you can also see not only is the disease pressure higher in this location in Ireland than the corresponding one in the U.K (Bracknell), but they have a really high peak coming on the 12th May which really high disease pressure. This cumulative period of disease pressure will have manifested itself as lots of copper blotches / yellowing of the sward. The image above is of spring Microdochium as you can see from the clearly visible seedheads.

So what’s to do ?

Reach for a fungicide to knock it on the head ?

Let it grow out because the growth rate of the grass is matching or exceeding the growth rate of the fungus ?

Well that kind of depends on where you are with nutrition, PGR applications and the like and clearly no one size fits all here.

If you’ve buttoned your turf down with a PGR for whatever reason then it’s likely that the scarring from the weekend gone and this coming week’s disease pressure will be worse because you aren’t growing the disease out. So maybe as a consequence you’ll either have to accept that (or rather your paying punters will have to) or apply a fungicide because at least uptake will be good from a systemic.

If you have a nice growth flush on greens which is growing the disease out as quick as it comes in then no worries really and I’d say a hardening mix will work fine to keep it at bay without applying a fungicide. Looking at the rainfall forecast, Ireland and the west of the U.K is likely to pick up higher pressure than central and eastern areas and so it is probably here where you’ll need to have your wits about you on the disease control front. Personally I’d be sitting in the apply a hardening mix, knock it back, grow it out and then settle into a PGR program but that’s just me.

Earthworms and insect damage

With the moisture and temperature will come more earthworm activity which has been mercifully on the back foot for 4-6 weeks because of the dry, cold April. The only benefit that we now have is some good drying winds which will allow worm casts to dry out between the showers and hopefully be easily brushed into the sward. Yesterday I measured nearly 4 mm of E.T over at Great Dunmow so as fast as we wet up, we will dry out. Again this will be less so across the west of the U.K and Ireland.

Now already we can see hatching Crane Fly larvae with the smaller species (yellower body) on the wing. It will be very obvious this week as we get the growth flush, the areas where insect larvae have been grazing or are still grazing nocturnally because you’ll have more vertical growth rather than thickening, tillering-type growth as the grubs graze a counter-sunk hole pattern in the sward. Obviously we have no control to apply at this time of year other than pathogenic nematodes so the emphasis must be on encouraging growth, better rooting (so the affect of the larvae is reduced) and maybe covering with a tarpaulin / silage sheet to remove the active grubs. I see a lot of images on Twitter and Facebook regarding this so if anyone wants to share their experience, negative or positive, please post a comment on the blog and I’ll pass it onto the masses 🙂

OK, that is me for another week.

All the best.

Mark Hunt