August 31st, 2021 – mini blog

Hi All,

Back from a tour of North Wales and 2 days at Silverstone MotoGP and complete with a somewhat suspect pose I agree, but (disregarding me) what a view after ascending Bwlch y Groes, the second highest pass in Wales on a motley selection of lovely motorbikes.

We largely kept off the speed camera / Welsh Police / traffic-ridden main roads and saw some beautiful scenery as well as lots of sheep !!!!

The heather was in flower so some passes were just stunningly beautiful and smelt lovely in the early morning air….a great experience…

Bit of a Welsh theme for me this year because next week I’m on hols in North Wales and at the end of the month I’m down on The Gower re-acquainting myself with a camper van, so blogs in September will be a bit hit and miss I’m afraid.

This week has been so cold and so dull over here in Leicestershire and that is entirely down to the north east wind direction pulling in low cloud and drizzle from The North Sea. When we set out on our trek it was cool, dull and uninspiring but as we headed west, things brightened up and by the start of the Mach Loop at Mallwyd, it was gorgeous. So a real east-west split with the weather and a north-south one as Scotland picked up the highest temperatures (as predicted).

So what is on the menu this week weather-wise ?

GFS output for 31-08-21 courtesy of Tropicaltidbits.com

General Weather Situation and outlook

So in summary form this week because I’m short of time in a short week for me.

As you can see from the GFS output above, high pressure sits to the north west of Scotland as we start this week and flowing air clockwise you can also see how England picks up a north east wind direction so situation normal for Tuesday I’d say and that’s pretty well how we are going sit for the rest of this week with cooler, duller weather on the east and warmer, brighter weather on the west and north. So similar temperatures to what we saw last week and of course there’s always the chance of some mizzly, drizzle pushing in off The North Sea into the north east / east of England during the week. This is more likely to be a.m. but is pretty much unforecastable. So high pressure is set nicely until of course I go away on my holiday when it all changes 🙁 (See below)

GFS output for 06-09-21 courtesy of Tropicaltidbits.com

So from Saturday the GFS suggests that we have a southerly low pressure system mouching in from The Atlantic. This will start to bring unsettled weather with some rain into Ireland and Wales on Saturday p.m. Being a southern-based low pressure the main thrust of the rainfall will be across the southern half of the U.K, with Sunday currently looking pretty wet. No sooner has that first low sloped off into The North Sea on Tuesday than another comes in from the west and brings more bands of sunshine and showers across the southern half of the U.K and Ireland of course. Thursday looks particularly wet and this low pressure pushes more rain northward as well on its leading arm so Scotland looks to have more in the way of rain as we go through to the end of next week. Next Friday looks like a bit of respite before more rain around on Saturday and the weekend after next.

So it looks like our dry spell will run the course of this week before changing markedly. Better take some waterproofs, my fly tying gear and plenty of New Scientist to catch up on, I need a relaxing break anyway to keep my head focused on the last part of my employment before I sign off at the end of October.

Agronomic Notes

Disease Synopsis

Well we find ourselves tip toeing into autumn although over in the Midlands and east of the country, it has felt like autumn to me for awhile now. Nature I think, thinks the same with Blackberries and Hawthorns ripening much earlier to my mind than is usual.

I think of September as a preparation month, time to get the house in order before what we know comes in earnest from October onwards. It is time as well after a cool, wet summer to keep pathogen populations down because for sure Microdochium has been around lingering all summer and don’t forget at the end of June we saw some of the highest disease pressure this year with aggressive disease and scarring.

The Growth Dynamic

Having worked on Microdochium nivale disease modelling now for some four years with my long-suffering tech geek Paul V, I know there are times of year when we see disease drivers very much tilted in favour of an aggressive outbreak but we don’t see it manifest itself on the actual turf. Now sometimes this is because there’s a control in place and it’s doing what it should do and other times, the rate of grass growth is high enough I think to prevent widespread damage to the grass plant. Simplistically the plant is growing out the disease faster than the disease can affect the plant. Now I’m sure it is a lot more complex than that, but that’s what we see.

So if our autumn periods are milder, why doesn’t this dynamic extend further into the year ?

Well have a number of factors at play here and the first one is light and specifically hours that the plant can photosynthesise vs. hours when it can’t….

So if we look at the respective hours of daylength and night length as we head into the autumn / winter (bit depressing this bit) you can see that by the time we get into October, hours of darkness is exceeding hours of daylight. Now this affects a number of processes in the growth / disease dynamic.

First off as we get less daylight, the grass plant has less time to photosynthesise and of course the quality and quantity of that light also decreases. I haven’t got DLI data yet for a full autumn / winter but if you look at the total amount of solar radiation in watts per m2 last autumn of which the grass plant only uses a proportion of, you get the idea why it is a lot harder for the grass plant to grow in the autumn / winter. (And of course I am not even looking at air and soil tempertaure!)

Not the best graph I’ve ever done but I lifted it straight off the Davis and the formatting options are…..limited….So below is the quantity of solar radiation (vertical axis measured in watts per m2) reaching our Throws Farm location from July, 2020 till the end of December 2020.

So less light hours and less light quality means growth is harder to support for the grass plant vs. the pathogen (which doesn’t need light to grow remember)

Of course there’s another factor that implicitly drives fungal growth (well Microdochium and a bunch of others) and that’s plant leaf wetness.

So we know dew formation in the autumn / winter takes place for longer, typically in the winter it starts just before sunset and carries on usually till a number of hours after sunrise provided of course we have the right conditions to evaporate that dew into the atmosphere. So that means wind and also a humidity low enough to allow moisture to move from the grass plant and soil surface to the atmosphere. Now that isn’t a given because we also know there are some periods of the weather during the autumn and winter (typically high pressure) when there is no wind, high humidity and continual plant leaf wetness. So you remove the dew at daybreak and it reforms again shortly afterwards (told you it was depressing).

Here’s a graphic below to show you a period in late January last year when we had just this type of weather…

If I paste in another Davis graph from last year, you can see how leaf wetness minutes increases during the autumn / winter and some days it hits the maximum of 1440 minutes (24 hours x 60 minutes) of leaf wetness meaning the plant leaf was wet continuously all day (now of course it might not be down to dew it could simply just be raining !)

So the vertical scale is showing number of leaf wetness minutes per day up to a maximum of 1440.

So in conclusion, at some point usually in October we reach a point where the plant has less ability to grow than the pathogen does and that’s when we start to see our favourite friend, Microdochium nivale in earnest.

Going into September, we do have a bit of a disease peak which drops off once we get into windier and wet weather and this peak is entirely down to dew formation and humid air.

So not off the scale disease pressure, a little higher in Ireland than England as it stands and one would hope perfectly controllable without recourse to use a pesticide (unless your location dynamics are set square against you) but I’d be thinking hardeners and irons myself.

The fact that we are seeing some higher Microdochium nivale levels coming into a dewy first week of September may also promote some Dollar Spot activity on sites that have a history of this disease so keep an eye peeled.

A late PGR app for outfield maybe ?

If it transpires that we move into a period of unsettled weather with moisture arriving after a period of relative dry then we can also assume that worm populations are likely to be highly visible (given the currently high soil temperature), so it might be an idea to think about applying a PGR and iron combination to outfield turf whilst it is still dry to slow growth (so you have less cutting and thus less smearing) going into the autumn / winter period. OK, it is a bit steep on the old budget but why not try one or two of your worse areas and see how it shapes up vs. untreated ?

Just a thought…

OK, that’s it for this week, no blog next week so I’ll be back on the 13th of September hopefully with an August update and a look at how we are set going into the autumn.

All the best.

Mark Hunt