October 28th, 2024

Hi All,

A walk through any woodland at the moment reveals numerous mushroom and toadstool species pushing through the canopy. Hardly surprising such has been the balmy combination of temperature and humidity this September / October and as we tip toe into November, the soil temperature is still tipping along between 11-12°C.

Great for fungal growth and as someone pointed out to me recently, it is also great for overseeded areas at the back end of the summer, with new seedlings thriving in the extended season. It wasn't so long ago that I would always mark the beginning of November as the beginning of real winter with the soil temperature typically dropping to 6-7°C in the 1st week of the month. Looking ahead to this week's weather, day time temperatures will still be in the teens and although the night temperature will be single figures, I think we will still go into November +5-6°C higher in terms of soil temperature than we used to.

It is immaterial in some ways what the driving force is, whether you subscribe to the factual theory that climate change is behind it or you spend your spare time watching conspiracy theories on YouTube, the reality is what we have to deal with here and now as turfgrass managers.

Over the next few weeks I have a super-busy talking schedule, beginning this week at Saltex on Thursday (Click here to go to the Learning Live Page at Saltex) when I'll be talking alongside the meteorologist Jim Dale and Head Groundsman, David Roxburgh. A little over 10 days later, I'll be talking at the Scottish Turfgrass Conference and a week after that, the Danish Greenkeeper conference.

Phewy, totally self-inflicted of course !

As I sit down and collate these talks, to put over facts in a meaningful way, I am struck by how our climate is changing so quickly.

For many turf managers, Microdochium nivale is public enemy no.1, but of late, Dollar Spot (Clarireedia homeocarpa) is in the fast lane and for many Scandinavian greenkeepers, the worst disease to deal with.

Why ?

Well because it now occurs on greens rather than outfield turf and it does so right in the middle of the playing season. Like Anthracnose, it has a slow recovery time for affected areas and can affect / detract from playability, whereas Microdochium is more of an autumn / winter disease and less damaging. Why is Dollar Spot on the move ? Well I feel that a changing climate is the main driver behind its transcendence up the disease ladder and particularly warmer, more humid air in the summer and autumn. Weather of the like that we will see this week for example....(what a nice lead in that is 😊)

7-day GFS projection for w/c October 28th, 2024 courtesy of tropicaltidbits.com

General Weather Situation

As you can hopefully see from tropicaltidbits.com, our weather this week will be dominated by a warm, high pressure system pushing in from The Atlantic. That in itself is not particularly usual for the end of October because normally we are in the middle of the hurricane season Stateside, and the recipient of Atlantic low pressure system after Atlantic low pressure system. The odd thing is that even with high sea temperatures, we aren't seeing the usual storm generation across The Atlantic and meteorologists for one are a bit stumped as to why ?

Image courtesy of The Met Office video on Blocking Patterns, find it here

What we have is a classic Omega Block as shown above, with high pressure positioning itself over the U.K & Ireland and protecting is from Atlantic low pressure systems (not that there are any currently like)

So the week ahead looks primarily dry, after some showers that are crossing the southern half of England today push off eastwards through the course of the day. A nice dry week is good news for those areas still saturated from the heavy rain at the end of September and during October. Not a particularly sunny week though as we will see a low cloud base most of the week, with a low number of sun hours per day and with light winds mid-week, a likelihood of mist and fog patches overnight and during the morning. This dry picture looks to extend right through the weekend with just some rain across the far north of Scotland at the end of the week. Day time temperatures are looking to be 12-14°C with night time temperatures down at 7-9°C.

7-day GFS projection for w/c November 4th, 2024 courtesy of tropicaltidbits.com

Weather Outlook - w/c 04-11-2024

As we progress through next week, the high pressure Omega blocking system slips eastwards and this is significant as I will explain later in the agronomic notes. As it does so, the trailing edge of the high pressure will pull up southerly, warm humid winds for the start of next week, so I think we will remain in the teens during the day, maybe higher. So for the west next week from Tuesday onwards you'll see more cloud and some rain push in from the west as Atlantic fronts try to push in and displace the high pressure.

Currently though the projection for the end of next week is that the high pressure stays in place and the Atlantic low pressure systems stay off to the west as you can see below. My money is on that southerly low will slip below the Omega block, form in the Bay of Biscay and then slip in to affect our weather eventually. At the moment though the U.K looks pretty dry except for the westerly coasts maybe (and Ireland of course) from Tuesday onwards.....

Agronomic Notes

So a couple of things to talk about agronomically as we progress into November.

DLI Light Comparison

The 1st one is light.

So I decided to look at the last 3 years from a light perspective and of course more specifically, PAR light. As we know there is a part of the light spectrum that the grass plant absorbs (shown above) and it is quantified in mols per m2 over a 24-hour period by a measurement known as the Daily Light Interval (or DLI for short). We measure it on our Davis weather stations using a cute sensor called an Apogee SQ212 shown above.

So first up, I calculated the total DLI from March 1st to October 21st from a Central England location for 2022, 2023 and 2024.

This was to see if we have had a duller summer this year (and last) vs. 2022, the year we had our last proper warm, dry / hot and therefore brighter summer.

The figures are shown below ;

Year Total DLI (01/03-21/10) in mols per m2

2022 5114

2023 3219

2024 3195

So you can see that in the last two years we have seen practically the same level of light from March 1st onwards to the October date at this location. Versus 2022, we have seen a 37% reduction in light levels. Food for thought if you are running lighting rigs.

I then decided to add up the number of days that the DLI has been high enough for Lolium perenne (DLI = 11 mols per m2) and Agrostis sp. Now for the latter I have used a DLI levels of 20 mols per m2 when the only online data is 30mols per m2 for Creeping bentgrass. I don't hold with that figure because I think it's for older Bentgrass cultivars like Penncross and Pennlinks, which had a much broader leaf growth habit vs. the newer Bentgrass cultivars which are much finer. So it's a SWAG jobbie, a Scientific Wild Arsed Guess as the late and great Dr James Beard used to pronounce. I just feel that 20 mols per m2 is more representative of Creeping and Browntop bentgrass species. If you disagree, let's see the data eh ?

Below are the 2 graphs showing the number of days per month of sufficient DLI light for both species in 2023 and 2024 from the same location ;

You can see for 2024, we had a much duller September with only 8 days of sufficient DLI light for Agrostis sp. vs. 18 the year before.

The main growing season for Agrostis, DLI light-wise is April - August, whereas Lolium commences a month earlier and hangs on a bit further into the autumn, though October only showed 16 and 10 days respectively across 2023 / 2024. October is definitely the drop-off month for Lolium. This means then that Poa annua (which we would presume has a much lower DLI requirement for growth) and moss actually, has a competitive advantage from the end of October to the end of March on fine turf and a little less on coarser turf. That period of advantage is extended in shade scenarios.

Maybe that gives some pointers for when we should be overseeding....

Disease Pressure

Looking at the way high pressure is set to dominate this week and maybe next, I can't help but think that we will see an upsurge in Microdochium nivale disease pressure over the next 7-14 days and particularly when the wind drops mid-week, this week.

Dove-tail that in when we look at next week and see we are set for some southerly winds, which would go down in my book as humid winds / temperature and that further compounds my hunch. A good time to apply a dew control I would say with good spray window availability for most and in doing so you will reduce the ability of the Microdochium fungi to grow substantially. With the cooler nights this week, the daily G.P will drop from its current 0.55-0.6 sort of level to more like 0.3. This is positive because it means that the longevity of any application will be extended with less removed by either cutting or the emergence of new growth that hasn't received the applied product.

OK, that's me this week, off to sort prep for Saltex, I look forward to seeing you there if you are attending.

All the best.

Mark Hunt