Back to my usual slot on a Monday morning and the last blog of July, wow hasn’t that flown by !
I thought this photo taken whilst out on a lovely walk around Medbourne in Leicestershire sort of typifies the weather we are having of late. We stayed dry but nearby they certainly didn’t…..
Watching Countryfile last night I was heartened to see a nice explanation of why we have gone from scorching temperatures at the end of June to a sunshine and showers scenario, not that I’m complaining too much on that front.
The presenter explained that the jet stream is running unusually low (red dotted line above) at present and this is allowing low pressure rather than high pressure to dictate this summer’s weather. In other words what I would call a jet stream trough rather than the more usual summer peak…..It’s good and bad for us working on turf though with some pretty hard tournament weather of late and of course disease but at least you won’t run out of water down in the south east of England
Ok enough of the pre-amble, I have a flight to catch later, so onto the weather for this week…
General Weather Situation
Monday is a west – east divide with plenty of showers affecting Ireland and the western coast of England, Wales and Scotland. During the morning these will consolidate to bring locally heavy rain to western areas with I think mid and North Wales, The North West and south west of Scotland chiefly in the firing line. Ireland will also see the showers affecting western coasts before they move across country during the late morning and early afternoon. For the east of the U.K, Monday looks like being a very pleasant day, dry with hazy sunshine and temperatures in the late teens to low twenties. Winds will be moderate to strong and from the south west. Under the rain you can expect more like mid-teens. As we progress through to Monday evening those showers look to fizzle out across western coasts.
Onto Tuesday and we have another raft of showers and longer periods of rain to think about. This time it will push in across the south west of England, Wales and The North West during the morning tand then move inland with the north of England likely to receive more than its fair share’s worth during the late morning and afternoon. They’ll also be another line of showers that will move diagonally (/) up from The South West across The Midlands (probably along the M5 I jest not) during the afternoon. These will be well dispersed so some areas will see them, some won’t. These two bands of showers will affect Ireland during Tuesday with the heaviest running over Connacht and Donegal with their southern cousins tickling along the coast of Munster during the morning. So again the south east of England and east will see less of the rain and enjoy another pleasant day until we get up to The Humber where we will run into that northern band. Scotland will see some showers in the morning up the east coast but in the afternoon, another band of heavier rain will push into The Western Isles and move eastwards across all of Scotland. Temperatures will be similar to Monday, mid-teens under the rain, high teens away from it perhaps touching the low twenties in the south east. Winds will again be moderate to strong and from the south west.
Wednesday looks to be the wettest day of the week at present. Starting off in the morning we have a strong rain front pushing into Kerry and moving quickly over Ireland so a wet morning is forecast. By the morning rush hour we will see rain, some of it heavy pushing into The South West and then moving on a north easterly trajectory up country across Wales and into the south of England and Midlands by early afternoon before pushing more east and north into northern England and southern Scotland by late afternoon clearing Ireland as it does so. Expect some locally heavy downpours. I expect it to last all day in some areas with showers consolidating through the evening and at the same time introducing a second rain front into the south west of Ireland which will again cross the country during the night. Winds will be strong to gusty I’m afraid and from the south west. Temperatures will be similar to the rest of the week.
Thursday sees that overnight rain across Ireland push north east into the north west of England and south west of Scotland in time for the morning rush hour. Meanwhile the departing rain from the south east will become potentially very heavy for a time around dawn before moving off across Kent and into The Channel. By late morning we have a very different weather picture with rain across the north of England and Scotland and a drier, brighter picture further south, the same over Ireland as that cloud cover breaks. At present I think the line of demarcation between sunshine and rain will be somewhere over the north Midlands / Peak District but let’s see. Again similar temperatures to the early part of this week, mid-teens nder the rain and high teens to low twenties where you see the sun. Still with a moderate to strong south westerly wind in situ.
Closing out what has been an unsettled week for the 1st week of August, Friday sees that low pressure system that brought rain across the U.K and Ireland mid-week begin to move off eastwards so a much better day is forecast for the end of the week. Still with a risk of showers across the west and south west of Ireland and also affecting the west coast of Scotland but overall a much drier day for nearly everyone with long spells of sunshine and some nice cloud pushing in later during the afternoon. Expect similar temperatures to the rest of the week with light to moderate westerly winds.
So how are we looking for the weekend, factor 30 or waterproofs ?
Well at this stage I see Saturday as being unsettled with some rain around and plenty of cloud. Winds will be much lighter so if you’re camping you won’t have to hang onto the guy rope to save the tent So not great for Saturday (but not a washout either) as there will be some sunshine amongst the clouds and showers of rain. Some areas may just be on the dull side and miss the showers altogether, my bet is eastern and south eastern areas may fit this bill. Sunday looks the better day of the weekend I think with less chance of rain and some nice sunny intervals but before you reach for the sun cream, there’s another low swinging in to affect next week.
As inferred above, we have another low pressure system slinking into the trough in the jet stream to bring us an unsettled start ot next week. Now high pressure is trying to push in from The Atlantic and this could do one of two things. It’ll either move the trough eastwards and introduce warmer and more settled weather from the west from mid-week, next week onwards or it will squash the low pressure system up which will mean it’ll intensify over the 2nd part of next week and bring more rain and wind for us all. Next week’s low will I think affect the east and central areas more than the west. So in summary, an unsettled start to next week with rain pushing in from the west and moving eastwards certainly through to mid-week, thereafter it’s a flip of the coin.
Disease and leaf wetness….
It’s hardly surprising when you have a month dominated by a trough in the jet stream that disease is an issue for many of us managing turf.
The culprits without a shadow of doubt are temperature and moisture or more spefically relative humidity, that is to say the moisture content of the atmosphere surrounding the grass canopy.
Leaf wetness is the driver for many of our turfgrass pathogens and it is a function of the moisture content in the atmosphere (relative humidity) and the drying potential as denoted by evapotranspiration. If we have a windy day then the drying potential is high even if we have a sunshine and showers scenario as we do currently but if we have low wind speed, low E.T then the drying potential drops and invariably the relative humidity increases….So on your golf course, sports pitch, stadium scenario, if you have areas which are more sheltered then you can expect the relative humidity and hence leaf wetness in those areas to be significantly higher.
Below is a run of two weather stations output from late October (ok I know the time of year is different, but the scenario is the same), the top graph is from an open aspect site, the bottom, a sheltered, tree-lined one.
You can see on the bottom graph, the effect of the trees is to drastically reduce the wind and this allows the humidity to increase to close on maximum over this 6-day run time.
On the top graph you can also see what happens when you go from a windy scenario to a lighter wind level, the humidity increases drastically from 77.4% when the wind is at full strength to 96.1% when it is at its lowest.
Looking at July and the sort of rainfall and humidity we have had I took this data from a weather station located in Banstead, Surrey.
You can see all the hallmarks of a summer trough event, high daily rainfall (40mm over 2 days mid-month) and a humidity that spends alot of the time > 90% with some days (marked in red) when the average was over 90%.
I also lifted some data from a weather station in Tipperary (one for you Colm :)) and the data is similar but not the same..
The Irish data shows a similar pattern in terms of high daily rainfall events and also some high humidity periods when the average > 90% but interestingly the maximum humidity didn’t reach the same levels as the Banstead location. I’m guessing this is because it is likely to be windier at the Irish location than the English one.
Either way both locations showed high humidity periods and this is what has been driving disease pressure in July but particularly in the latter part of the month over here in the U.K.
So if you’ve been looking at mycelium on Microdochium nivale, you now know why this pattern of weather has been very conducive for the development of this disease…..
In other scenarios I’ve seen lots of copper blotching from Microdochium nivale (old man’s Fusarium to keep some of you happy) across swards and this has definitely been due to the dynamic between grass growth and disease development. What I mean by this is that with good temperature and consistent moisture, grass growth has been close on optimum of late and so the disease in some cases isn’t scarring because it’s being grown out as fast as it is developing.
Microdochium isn’t the only foliar pathogen doing the rounds at present with Dollar Spot, Leaf Spot and Red Thread also reported or observed.
Leaf Spot has been a significant issue on perennial ryegrass on sports stadia this month particularly those with reduced air flow (and the graphs above illustrate why nicely I think) and I reckon the trend will continue until we move out of this trough pattern in the jet stream.
Another disease notable in July on some sports pitches has been Brown Patch and this really is a humidity-orientated disease. It likes high temps, but humidity is the key driver.
So we are having a tough time of it disease pressure-wise and at a time of year when normally you’d be hoping for drier surfaces and low disease pressure. The concern for me, particularly in the case of Microdochium nivale is that when we see it in the summer, we tend to carry this disease through into the autumn.
Just finishing off a slightly doom and gloom scenario, I saw the start of Anthracnose mid-July as predicted and I expect to see more of it over the coming couple of weeks reflecting disease pressure that started in late June and will only have been encouraged by the run of weather lately. 2014 and 2016 proved to be high pressure periods for this disease and as you can see from the date stamp on the above slide, mid-August is typical for peak activity.
I appreciate for many applying a fungicide at this time of year and even contemplating it is not ideal and we know with an optimum growth rate the longevity will be compromised for sure. It is also worth pointing out that if you are applying a systemic fungicide to active disease I would estimate that it takes at least 5 -7 days for the A.I in the product to build up sufficient concentration within the grass plant to halt its progress.
So if you apply on a Monday and see active disease two days later then you can rest assured that the disease was already active inside the leaf before you applied it and the fungicide isn’t present at sufficient levels to slow its progress.
I still think the best option is to try and maintain plant health and vigour (remembering that the last thing you need at this time of year is a weak plant) when we are in this type of weather pattern, but saying and achieving it can be challenging to say the least.
Rootzone capabilities and nutrient leaching….
When we get these summer trough patterns it’s clear that we also receive high daily rainfall events and you will all probably have your own tale to tell on that one. Reading University recorded 36mm falling in one hour last week and I have been told (cheers Paul) of weather stations measuring a rain rate of 200mm / hr at some points during storms, that’s 8″ per hour !
That level of rainfall is at tropical levels and it brings with it issues for us, particularly on rootzones that aren’t capable of moving that volume of water from the turf surface to the drainage (hopefully) layer. That’s why I’m a big fan of vertidraining at this time of year as well as solid tining prior to topdressing. This type of aeration, at this time of year, achieves a lot more than you think because not only does it relieve compaction and facilitate better water movement from the surface but it also allows the rootzone and most importantly, the grass plant to breath and that’s key to plant health, nutrient and fungicide uptake. If you have a grass plant that is growing in a low oxygen environment then it will be working at sub-optimal levels in terms of uptake of that you can be assured.
Compact vertidrains and 5-6mm solid tines create very little disruption on the surface, particularly if they’re followed by topdressing and a roll, but their benefits are long-lasting.
The other point I wanted to make about these type of rainfall events is nutrient loss through leaching. For sure when we have high daily rainfall followed or preceded by a cool night, we will see significant loss of nutrient from the rootzone by leaching. The sandier the rootzone, the lower the CEC, the more likely this is to occur, so keep an eye out if you’re in this type of environment and maybe try to tighten your application intervals so the plant is kept at a consistent nutrient status.
Ok that’s it for this week, have fun, stay sane and enjoy the sunshine if you see it
All the best..