The warmest start to November on record for some of us yesterday with temperatures in Wales exceeding 22°C, but if you were in the south of England you were lucky to see half of that as the fog failed to lift for most of the day. This time of year it’s all about leaves isn’t it, no sooner have you cleared them all up, than they are joined by some more…I just about completed this task yesterday when the Air Ambulance had to make a landing in the Rec behind my house. You’ll notice the absence of leaves around the helicopter, guess where they all ended up ?
If you were lucky enough to see the sun and feel that heat I think it felt almost unnatural for this time of year and looking ahead I don’t see things changing anytime soon. It may not only be the mildest start to November, unless the outlook changes soon (and it can do) it may well be the mildest November on record, but we’ll see, plenty of time for things to change yet…..So how are we set for the week ahead ?
Fog is a major issue as we start Monday, particularly for the south of England, extending up into The Midlands as well. The west side of the U.K and east coast of Ireland should have more chance of seeing the sun earlier, but elsewhere if you have the fog, it may take up until lunchtime or even later to clear and for the sun to break through. So a cloudy, dull start to the day, but with the sun breaking through later temperatures will climb into the mid to high teens. As is usual on foggy days, they’ll be only a light south-easterly breeze to move things along. Pretty much a dry day for everyone save for some coastal drizzle over North West Scotland early afternoon. As we go into Tuesday that fog may well re-appear in some places as the temperature drops.
For Tuesday our dry start to the week comes to an abrupt end as that south easterly wind pushes some rain off the continent and into the south of England by early morning. By the rush hour that rain is into Wales and The Midlands and heading north. Elsewhere it looks another dry day with the best chance of sun along the eastern coast, but in general it’ll be cloudier everywhere than Monday because of that rain front. By mid-morning that rain is into North Wales and northern England and by lunchtime it’ll be into the borders of Scotland. There’s a chance in the afternoon that the westerly end of that rain may intrude into the east coast of Munster and Leinster as it heads north. As we reach dusk more rain is pushing into southern England and tracking north. During the evening the wind swings round to the south west and that’ll push the northerly rain over to the north east of Scotland and the southerly rain will head north east to affect the eastern coast of England. Temperatures will be a little down on Monday because of cloud cover and rain so expect low to mid-teens to be the order of the day and winds to be light to moderate.
By Wednesday morning that rain will have departed stage east and left behind some dense cloud cover, heavy enough for some light rain and drizzle over most of the U.K and Ireland first thing. As we progress through the morning that rain will be isolated to The Lakes and the south west of Scotland, but there’s more on the way unfortunately. Elsewhere it looks pretty dull again as more cloud is pushed in from The Atlantic, a portent of more rain for all of us. So by mid-afternoon, maybe earlier, we have rain pushing into the south west of Munster and the south west of England and this will quickly track inland. So through Wednesday evening that rain will track across Wales and be reasonably light, whereas the rain affecting Ireland will push across the whole country and be heavy in nature with localised flooding possible. So another mild day, with temperatures in the low to mid-teens but no risk of fog as the wind picks up to a moderate south westerly.
As we go into Thursday that rain has lightened but spread out so Thursday morning looks likely to start showery across all of the U.K and Ireland, but most of the showers will be confined to the western coasts of the former. By lunchtime that rain front has cleared Ireland to leave some sunshine behind and the showers affecting the west of the U.K will tend to track north east into northern England and Scotland later on in the day. So away from the rain another dull day, but with a chance for the sun to break through in the east particularly and if it does the temperature will pick up nicely to the mid-teens accompanied by a brisker south westerly wind.
Closing out the week we have more rain on the radar for Ireland and the south west of England, but this front is moving much faster and clears Ireland by dawn to give a sunny start to the end of the week. Elsewhere we have rain over most areas in time for the morning rush hour, but it’ll be potentially heaviest across the north of England and particularly Scotland. With this being rain from The Atlantic, it’s possible the south and south east may miss most of it to give a dry day on the whole for Friday. By lunchtime this northerly rain should have cleared all but the far north east tip of Scotland to leave behind a nice, sunny day and in that sun temperatures will pick up into the mid-teens for most areas, so a nice finish to the week.
The weekend looks a bit of a mixed bag really with a dry start to Saturday, but rain, some of it heavy, will push into Ireland and the south west of England early doors and move north eastwards inland. Central and southern areas of England may not get this rain till later on Saturday (or may miss it totally) so it’ll be touch and go for fireworks on Saturday night (Note Bro). This rain will still be around early doors on Sunday to give a dull, damp day for many, possibly brighter in the west, but more rain looks like arriving later on Sunday for a repeat showing unfortunately. That makes Sunday a day to sit in and watch Marquez skittle Lorenzo at the first corner while Rossi rides on to seal his world championship…(I’ve just woken up..)
Pretty much bang on last week with the projected forecast for this week suggesting the high and low pressures would tilt to give a south westerly air stream and a more unsettled picture, so how are we looking marching into mid-November ? Well similar in a way with that ’tilted’ theme still much in evident but the high will extend it’s influence into the south and east of England so a weather map of two halves for next week me thinks.
For the west and north, you’ll be closer to the low pressure so that means windy and unsettled with rain pushing through across all areas for the start of next week. Thereafter things settle down a bit with that wind and rain very much isolated to north of a line drawn diagonally up from Kerry over to Fife. Further south they’ll still be some rain around but they’ll be less of it and as you head towards the south east, you’ll be closer to the high pressure so more settled, but cooler here and potentially a return to some foggy nights. I can’t see it getting cold though because the air stream will still be south westerly and that will pull mild air up from the continent for the foreseeable. Can’t complain for the middle of November.
First off we’re going to catch up with how the year is shaping up GDD-wise vs. past data…
Now here’s an odd one because you can see that the GDD total y.t.d is 1562 and that’s the lowest cumulative total for the last 5 years, even the year of the cold winter / spring, 2013, had recovered to a higher cumulative total y.t.d by the end of October, so why is 2015 low ?
Well we had a very slow start to the year, but September and October 2015, have come in lower than any other year, so although we’ve had warm spells in both of these months, we’ve also had some colder air flow as well. For certain that’s the peak and trough of the jet stream coming into play…
Comparing 3 sites across the U.K you can clearly see a continuation of the yearly pattern with Long Ashton picking up the more temperate conditions in the spring and The Oxfordshire lagging behind, pretty much on a par with York for that matter. As the summer gets into its stride, we see the central Oxfordshire location ramp up in July and August, so much higher temperatures there than either of the other two locations. For September and October we revert to the same pattern as the spring, i.e with Long Ashton picking up the milder temperatures and York / The Oxfordshire, the cooler, easterly airflow.
What significance is this to turf management you may ask ?, well there’s plenty of information we can glean from this.
For example, we know The Oxfordshire will have suffered the highest stress levels of the three sites. If we look at potential grass growth and therefore cutting requirements, Long Ashton comes in 9% higher than The Oxfordshire and a whopping 25% more than the York location, worth knowing and worth budgeting for….
Looking across the Irish Sea we see a similar pattern for the year and the month of October, though as always, milder in Valencia, because that’s where the south-westerlies arrive first.
If you compare within the Irish sites you can see some pretty big differences with Claremorris in the beautiful county of Mayo, having a cool year with the lowest GDD monthly figures for each month, 20% down on Dublin or Cork for example. Apart from Claremorris, the sites are very similar through the spring with the exception of Valentia and this follows the same format as the U.K sites i.e the south west picks up the more temperate air and there’s nowhere more south west than Valentia !!!!! Through the summer Ireland is cooler as we know and seldom reaches the dizzy heights of the south east of England, but that means less stress lads, so we can smile about that one. For the autumn the Irish and U.K sites are very similar with Valencia and Wexford showing similar GDD information to central and south western U.K.
Looking at October as a month for grass growth and disease activity…
As is becoming the norm now for the U.K and Ireland, October (probably alongside August) represents one of the highest disease pressure months we have to deal with. So although it hasn’t been the warmest October according to GDD, why do we see such high disease pressure ?
Well there are two main factors driving disease, air temperature and leaf wetness or more specifically, longevity of leaf wetness. If you look at the Growth Potential figures for October from the sites we have data for, you see a clear pattern where sudden increases in air temperature drive up the disease pressure…
If we look at the peaks in Growth Potential for both the U.K and Ireland, we can see 5 clear peaks through October when the G.P increased rapidly. Not only will this drive grass growth, but it’ll also drive fungal disease development and that means Superficial Fairy Ring (Think how many mushrooms there still are about in the fields), Red Thread and public enemy number one – Microdochium nivale.
So when we’re in a peak situation like the last weekend, the balance is tipped very much in favour of disease development. You’ll also be cutting more regularly because the grass is still growing vigorously so the efficacy of any fungicide application will be limited on two fronts ;
- Removal of active ingredient in grass clippings…
- Ability of the fungicide to slow down the growth of the fungus enough to stop it becoming pathogenic..
So it’s more than likely that you’ll have seen this type of scenario somewhere on your turf surfaces when you came in this morning…
The above image was taken from my front lawn (unfortunately) but there’s only one area affected and that’s the part of the lawn that sits in shade…
This brings me onto factor 2 in the disease-driving equation, that of leaf wetness or specifically the period of leaf wetness…
I know it’s not great for me to say this but we’ve had a perfect storm of late that is driving disease development. Sudden increases in air temperature, heavy dews and of course some heavy rain as well which has increased the moisture content in the ground and led to the formation of guttation fluid. I’ve talked about this before but it’s the droplet of solution that’s secreted from the tip of a grass leaf when soil moisture levels are high and conditions are favourable for dew and guttation fluid formation. Notice I used the term ‘solution’ and not ‘water’ for guttation fluid and that’s because this guttation droplet is full of nutrients and sugars, whereas dew is just water. I took this picture last Thursday after an overnights rain..
You can clearly see dew along the leaf margin, but also the droplets right on the tip of the grass plant. This is guttation fluid and right back in 1968 scientists in The States linked the presence of guttation fuid with disease development, in that case it was Dollar Spot.
So let’s look at the weekend over a 24-hour period and analyse when conditions were favourable for dew and guttation fluid formation…
So what are we looking at on the graph above ?
Well, firstly let’s talk dew point, a term often banded around, what does it mean ?
The dewpoint temperature is the temperature at which the air can no longer “hold” all of the water vapour which is mixed with it, and some of the water vapour must condense into liquid water. The dew point is always lower than (or equal to) the air temperature.
This took me awhile to work it out and more than a bit of head scratching on my part (little wonder I’m thin on top then eh? :)) but essentially what we’re saying here is that if the air temperature remains higher than the maximum temperature at which dew will start to form, (Maximum dew point temperature), then no dew forms. Once the air cools below the maximum dew point temperature then water vapour in the air condenses to form dew on the grass plant.
This is really neatly shown on the 24-hour graph above.
Look at the period between 15.00 and 17.00 hrs on 31-10-15 (circled in red), we can see the air temperature is higher than the maximum dew point temperature and so no dew forms. You can also see that as a consequence of this the humidity drops as well because the water vapour in the air is not condensing (the formation of liquid water drops from water vapour)
Once we reach 18.00 hrs, the air temperature has dropped below the maximum dew point temperature and so water begins to condense in the atmosphere, the humidity increases and dew forms on the grass surface by condensation. If we follow this right through into the next day, at no point does the air temperature exceed the maximum dew point temperature and so dew can form all the way through the day. As a consequence, the humidity never drops despite the fact that it’s become day.
Taking the 24 hour period as a whole from 12.00 hrs on the 31st October through to 12.00 hrs on the 1st of November, it looks like there was only 3 hours in that period when the air temperature was high enough to prevent dew formation.
So the plant leaf is sitting wet for 21 hours of a 24-hour period.
Even if you removed the dew at say 7 a.m. on Sunday morning, it and guttation fluid would have re-formed again soon after because the air temperature sat lower than the maximum dew point temperature.
We have very high disease pressure currently because ;
- The disease population is growing at a very fast rate because of sudden increases in air temperature and long periods of leaf wetness that facilitate the formation and movement of fungal mycelium across the plant leaf…
- Fungicide efficacy is also compromised currently because clipping yields are high due to high G.P levels promoting strong growth so expect less longevity from your fungicide application…
- The rate of development of new growth that won’t be covered by any contact fungicide is also high because of a high G.P. So this is growth that has occurred after you have sprayed your contact fungicide and unless that contact is root-absorbed it won’t protect newly-emerged grass.
The proof of the pudding here is the amount of active Microdochium nivale present on non-sprayed areas like lawns, winter season pitches, golf tees, approaches and fairways. It is everywhere you look at the moment.
What’s to do ?
Well obviously we have to try and meet the disease pressure head-on, but our fungicide options are limited because of a low number of different active ingredients (Lots of product names, but not a lot of choice when it comes to active ingredients and even less when you talk about effective active ingredients)
- Try to ensure the plant leaf is as dry as you can so remove the dew from your greens as early as you can and if practically feasible repeat the exercise on the shady / poor air flow greens as these are likely to be the ones where the leaf sits wettest. (And dew will re-form)
- Make sure that your fungicide applications are appropriate and for me that means using a Triazole-based systemic and mixing in a contact like Iprodione to try and maximise the number of effective active ingredients that are present to suppress fungal growth
- Use iron, preferably as acidifying as possible to try to dry the leaf out and acidify the leaf surface which we know will reduce the rate of growth of Microdochium nivale. This option is relatively low cost but can be very beneficial particularly on outfield areas where spraying of a fungicide is either not permitted (on the continent typically) or not cost-effective. Personally I’d try and intersperse fungicide applications with iron rather than just apply together because that way you are spreading out the suppressive effect of the applications over time, rather than applying all of the materials at the same point.
- Keep your grass plant healthy, don’t starve it because a weak plant is just as likely to get disease as an over-fertilised plant, so try and sit between the two. Like everything in life, a balance is key. (Easy to write, hard to achieve)
Looking ahead with the slightly cooler temperatures and some wind from Tuesday onwards, our disease pressure has dropped from the high of the past weekend, but it’s likely to increase again as we approach the end of the week..
Ok, this started out as a short blog, I hope it proves useful to you
All the best…