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  • Writer's pictureMark Hunt

May 7th, 2024

Hi All,


First up, my apologies for no blog last week. I was laid up with some crappy bug, still not 100% but tempus fugit and all that....


So we are into May and the weather has turned on its tail with some warmth and periods of dry weather, though yesterday I know, some areas in the south picked up another dollop courtesy of a very slow-moving rain front. I was fly fishing at Rutland Water and praying for that cloud cover to arrive, it pitched up as a cloud bank in the distance and then slinked away leaving me a tad frustrated and sun burnt. One point for this week, U.V levels will also be on the rise so cover/ protect that skin accordingly.


Nature is in overdrive with the hedgerows visibly growing and crammed full of Hawthorn blossom, Keck (Cow Parsley), Campion, Stitchworth, Forget-me-Knots and Speedwell. I love this time of year, everything is so so green and lush. That growth overdrive looks to continue this week with some nice temperatures on the way and some long overdue dry weather.



Article above reproduced courtesy of The Guardian (read the full article here)


Speaking of nature, I got sent this snippet from The Guardian newspaper (cheers chap) regarding the use of soil conditioners for the control of earthworms. Looks like the press has got hold of the topic, with golf courses clearly implicated if you read it. It'll be interesting to see where this one goes, if anywhere......


General Weather Situation


The GFS snippet from tropicaltidbits.com above shows a high pressure peak sitting south of the U.K in The Bay of Biscay. During the week it will push up across the U.K & Ireland and bring us calmer, settled conditions. As it stands now, this high pressure ridge looks to stay in place till Sunday, so we have a good spell of stable dry weather for most areas. As that high pressure builds, so will the air temperature, so expect to see the highest temperatures later in the week and extending into the weekend, maybe with a thundery breakdown ?


Scotland will sit in the high teens increasing to the low twenties by the weekend, whereas England and Wales will hit 20°C from the off and by the weekend could be into 23-24°C. Ireland will sit behind temperature-wise because of a higher level of cloud cover and some Atlantic fronts that will push into Ireland and Scotland during the week, so more like 15-17°C for Ireland during the week, still nice like and crucially dry for most areas of Ireland. The blot on the landscape rainfall-wise will be across Wednesday pm into Thursday pm when rain will cross the north of Ireland and push into the west and north west of Scotland and move into more central areas during the course of Thursday. It will also linger across the far north through to Friday.


Other than that, a nice week, unblemished by rainfall in most places, with light winds (so not excessive E.T levels initially) and pleasant temperatures. Those winds will be initially from the north but will spin on their tail to southerly and later in the week pick up strength and come in from the east. Then the E.T will pick up markedly. As will be the pattern with day temperatures, night temperatures will build during the week into the low teens so that means no handbrake to growth and optimum G.P levels this week. My only caveat is that the GFS output has some showers across central England on Friday and Saturday, maybe thundery outbreaks, but they are un-forecasted anywhere else so let's see.


Weather Outlook


So after a pleasant week , what does the following week hold, an extended dry spell or a wet breakdown ?


Well the weather picture for next week is finely-balanced, but at this stage we look to be heading towards a spell of wetter, cooler, weather to begin next week as two low pressures come into play. As it stands now (and this can change), low pressure will form in a jet stream trough in The Bay of Biscay and pretty much stay there all week. This will push south easterly winds into the weather picture and successive rain fronts across the south west of Ireland, south / south west of England moving north, starting next Monday. Most of the forecasted rain next week is for the southern half of the U.K and Ireland, as is usually the case with a BOB low. (Bay of Biscay low) Tuesday sees a repeat with a more consolidated rain front pushing across Ireland, Wales and England, this one will reach northern England and The Borders during Wednesday. Possibly a temporary hiatus on Wednesday with less in the way of rain before showers push in later in the day and continue through Thursday and Friday. As we approach the weekend, high pressure looks to intervene again and dry things up a tad. With low pressure to the south, the winds will be south easterly and likely result in normal temperatures for the week with mid to high teens I'd say and reasonable night temperatures.



Agronomic Notes


Growth Flush


OK, well the 1st thing to discuss is the effect on the temperature uplift this week on growth. As you can see from the G.P projection for this week (alongside actual readings for May 1st - 6th) taken from a location near Bracknell in the south of England, Growth Potential figures are pretty much nailed onto maximum for the week ahead up to and including the weekend. For Ireland, this flush will be less marked, a little less for Scotland too, but the relevance is two-fold, one because we should be able to get some dry cuts in this week and two, because if next week's weather pans out, it looks like a wet week with limited dry cuts. So if you want to bring wayward roughs, semi-roughs, fairways, outfields (delete where applicable) under control, this week is the week to chuck everything at it resource-wise. Similarly on fine turf, with some good growth levels this week, dropping in a light verticut and topdressing could be well-timed and appropriate.


Disease Activity

Looking at a snippet from Prodata Reports for a golf club in Kent, we can see this May so far has been characterised by high humidity and some mild day / night temperatures, in other words, a calling card for Microdochium nivale. I have highlighted the Smith Kerns column in red, with probability levels sitting in the high teens for the first six days of this month. So this week's growth flush may well come in handy to grow out some scarring if indeed you were caught earlier on this month. Rainfall, temperature and humidity tend to increase diseases like Fairy Ring and Red Thread, so with the combination of temperature followed by rainfall, it wouldn't surprise me to see some more activity next week.


Anthracnose Trigger ?


Now with temperatures edging up into the low twenties at the end of this week and weekend, we are getting close to the initiation temperature for spore germination for Anthracnose - Colletotrichum cereale. Currently we work on the basis of 3 successive days of 25°C followed by high humidity / rainfall to allow mycelium development. Well we will be close to this across Wales, The South West and southern half of the U.K later this week. Close, but not quite meeting that temperature threshold. A couple of variables, organic matter heats up more than air temperature at times, so from a localised perspective, we could see 25°C and undoubtedly spore germination will take place at temperatures less than 25°C. For me, I think I'd probably mark down this week as a potential trigger, particularly because it is potentially followed by rainfall / humidity next week.


Bear in mind I am not saying Anthracnose will develop this week, rather that potentially the complicated development pathway for this disease could be initiated this week.


This disease is a strange one, first up, the rate of fungal growth of Anthracnose is slow, in the lab, about a 1/3rd of its nippy cousin, Microdochium. This means it is more susceptible to disruption as it develops on the surface of the grass plant. Whereas Microdochium is more of a 'smash and grab' disease, Anthracnose, takes a step back, ponders, measures up and then removes the window methodically ☺. Even when the fungus has penetrated the epidermis of the grass plant it doesn't immediately develop into a pathogenic disease with discernible symptoms. Rather it sits inside the plant cell in a biostatic phase followed by a necrotrophic cell-damaging phase, if the plant is subjected to stress. There is a great article on Anthracnose by the USGA here


In my experience, we can often see a trigger event occur in the U.K & Ireland, but not the following symptoms of Anthracnose Foliar Blight and that is because either the trigger is not followed by humidity / plant leaf wetness or the temperature wasn't consistently high enough for spore germination. The USGA article mentions temperatures of 29°C or above favour development of this disease, in my experience in the U.K and Ireland, it is less. From a practical perspective, it comes down to mitigating plant stress as and when it is likely to occur and / or if you are stuck in a cycle of Anthracnose development over successive years, you need to break the cycle with a preventative fungicide. Fortunately we have a number available to us.


GDD - Monthly & Annual Cumulative Totals - The Oxfordshire, U.K



Next week I am going to do a full comparison looking at rainfall and GDD around the U.K & Ireland, but I am in catch up mode, so for this week, I will just look at our default locations stats.


So April '2024 came in at 110.8 total GDD (using a 6°C base temperature), not our highest April total and kind of more in keeping with kind of 'normal'. It brings to an end a run of 4 successive months of high GDD that we have endured. Put it in context for the year-to-date though and we are still way ahead.



In 2024, we reached a figure of 303.6 cumulative GDD at the end of April, in 2023 this figure was 220.6 and in 2022, 222. Versus last year we have amassed nearly 40% more GDD.


When you graph out the cumulative GDD year-on-year, 2024 vs. 2023 vs. 2022, you can clearly see the difference in 2024 vs. last year and the year before.



So from a practical perspective for example, Poa annua var. reptans began its main seedhead flush (at this golf course location we know it occurs at 180 total GDD measured from 01-01) on 18-04 in 2022, 19-04 in 2023 and 25-03 in 2024 !


That's 25 days ahead of prior year.


For me, that's the practical relevance of measuring GDD.


Match up practical events such as Poa annua seedhead development, weed emergence, plant parasitic nematode development, etc with GDD at your facility and track accordingly. More growth = more cutting = more energy usage = more machinery hours - more blade edge wear (You can tell I have sat through a Tom Stidder talk 😀)


Another example of practical relevance from a measured parameter.


I repeated the exercise comparing cumulative G.P year-on-year (rather than cumulative GDD) and the results were very similar. For example, at the end of April 2024, we reached a cumulative G.P of 29.75, in 2023, the figure was 22.29. We reached a cumulative G.P of 22.29 in 2024 on 05-04-24, whereas GDD gave 06-04-24, so there's a day difference in a year-on-year comparison between GDD and G.P.


OK, that's me for another week, head frazzled :)


All the best.


Mark Hunt






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