Indian summer for September?
September last year will be remembered for a final respite in the relentless summer rainfall and the chance to dry out. In fact, in the short term five-year average September has proven to be the driest month of the year for significant parts of the country. But a review of the long term averages indicates September begins the shift to autumn conditions and the first of four consecutive months when rainfall averages over 100mm for the country.
Most notably, in September sunlight levels start to fall dramatically and evenings start to get significantly cooler. Typically night time temperatures are an average 2°C cooler in September, compared to August, with 40 hours less sunshine - a reduction of 25%.
| Long-term average September weather |
| |
High Temp |
Low Temp |
Av Temp |
Sun |
Rain |
| UK |
16°C |
8.5°C |
12.2°C |
120 hrs |
102 mm |
| N. England |
16.2°C |
8.6°C |
12.4°C |
121 hrs |
84 mm |
| S. England |
17.9°C |
9.4°C |
13.7°C |
140 hrs |
65 mm |
| Scotland |
13.8°C |
7.3°C |
10.5°C |
98 hrs |
142 mm |
| Wales |
16.1°C |
8.8°C |
12.4°C |
125 hrs |
123 mm |
Whilst turf growth may still continue, the ability to recover from damage or maintenance operations could be seriously reduced. The effects of pest or disease attacks that may be outgrown during August without intervention, may become far more evident and have a longer term effect in September.
For those hoping for an Indian Summer, to extend playing season and enable much needed turf maintenance, the chances have significantly increased over recent years. In the past two decades, the UK as a whole has experienced below the long-term September average rainfall in 70% of years, and above average sunshine in 65% of seasons; including each of the past six years. You need to go back over 13 years to find the first season with below average temperatures in September, highlighting the potential for turf to keep growing longer in the autumn.
Turf managers need to be aware of this change with fertiliser programmes. The alarmingly increasing cost of fertiliser in recent months may see turf managers tempted to cut back earlier, but if turf is continuing to grow, it needs to be fed, albeit at a lesser rate as growth slows. Failure to provide sufficient nutrients at this stage could result in plants drawing on root reserves and, with no further opportunity to replenish stocks before the winter, leaving plants more susceptible to long-term damage and problems over the winter.
Over-seeding opportunity
Providing sufficient nutrients is especially important with autumn reseeding, where new turf needs to get established as quickly as possible before the autumn cool down and the pressures of winter play. Warmer September conditions may enable over-seeding later in the season, but it will inevitably turn far colder in October - falling by a further average 3°C.
The success of September over-seeding could be significantly enhanced by regulating the growth of existing turf with Primo MAXX prior to sowing, to reduce the competition for light and nutrients for the new seedlings.
Over-seeding gives the much needed chance to patch worn or damaged areas, as well as an opportunity to introduce turf species that may be better able to adapt to changing climatic or growing conditions. Despite the above average rainfall every month through the summer for most areas, long-term trends indicate drought tolerance will clearly be of increasing importance in future years. Turf managers may also be looking at grass species better suited to low fertility situations that will withstand periods when rain has leached out nutrients, or reduced fertiliser input regimes.
However, such a mixed-species sward will increase challenges for turf managers. Whilst Fusarium Patch risk may be reduced from growing under lower fertility conditions, for example, the original turf species composition will be far more susceptible to attacks from disease such as Dollar Spot or Red Thread where fertility is reduced.
Equally, if irrigation is reduced on the more drought tolerant new species, the stress induced on the original turf is likely to lead to increased Anthracnose attack and reduced ability to withstand attacks from nematodes or other pests during the increasingly frequent protracted periods of hot, dry weather.
Lush growth
September turf nutrition does need to strike the careful balance between providing sufficient to support healthy growth, but avoiding causing lush growth that is most susceptible to Fusarium Patch infection. There is a high risk this season of the pathogen having survived during the relatively wet summer conditions this year, when it is more likely to break out into a full-blown attack as conditions cool through September (below).
Turf managers should be inspecting any areas highly susceptible to attacks whenever conditions are conducive, especially during any humid, thundery weather. Turf with a high Poa annua content is likely to be the first affected, but if the disease spreads all species can be affected. If the indicator turf areas show signs of infection occurring, there is a good chance more widespread attack will follow and a fungicide with good curative activity, such as Daconil Weather Stik will help to minimise spread.
However, repeated trials by the Sports Turf Research Institute have shown that the use of weather and disease forecasting to predict when there is a high risk of Fusarium Patch attack, and applying a fully systemic preventative fungicide, such as Heritage, prior to symptoms being seen can maintain a higher level of disease control, improved turf quality and reduce the overall number of fungicide applications made through the autumn and winter period. Turf managers can currently undertake a free trial of the internet disease forecasting service - www.greencast.co.uk - to evaluate how the predictions and advice matches Fusarium disease risk and timing on their sports turf.
The problems with Red Thread, which has proven a widespread issue for many turf managers in the wet, warm conditions over the summer this season, should begin to recede as conditions cool during September. But there remains a risk during any periods of particularly mild weather. The disease rarely causes serious damage to plants, but looks unsightly on quality turf surfaces. An application of Daconil Weather Stick for Fusarium will can control and prevent further Red Thread attacks.
High disease risk in the prevailing weather conditions will also pose a particular threat to new turf seedlings, where a programmed fungicide approach can help to ensure successful establishment before the rigours of winter set in.
2007 lessons
A review of turf disease attacks in 2007 (below) reveals the relatively warm temperatures kept Fusarium Patch risk low for the early part of the month, but hit with vengeance on the 16th September in Scotland, with a spell of wet weather and cool nighttime temperatures; in Southern England the onset of attacks started around a week later.
In contrast, South East England suffered from prolonged Antrhracnose and Dollar Spot pressure through the early part of the month, whilst only Dollar Spot was the real threat in the South West. Scotland experienced little or no Anthracnose and only low Dollar Spot risk.
Worm burden
Moist early autumn conditions during September are also likely to see worm problems resurface. Whilst a high worm population is indicative of healthy soil and good biodiversity, worm casts are slower to dry out in the autumn and smear across the surface during brushing or mowing. The surface deposits spoil the turf underneath, disrupt ball-roll on greens, blunten mower blades and can allow Poa or weeds to germinate and ingress. The damage caused by rooks and badgers rooting out worms can prove disastrous.
Regulating autumn grass growth with Primo MAXX applications up until early October can reduce the frequency of mowing by 50%, thereby reducing the number of worm casts spread, or giving greater flexibility for mowing timing to allow casts time to dry off and be brushed clean. Furthermore, reducing the clipping yield will limit organic matter return to the soil and reduce worm activity.
More recently, evidence of a new worm species, Microscolex phosphoreus, has increasingly been found during the autumn. Although only tiny and producing small casts, the sheer numbers involved have been reported to be causing widespread damage to golf and bowling greens where it occurs. Similar in appearance to small earthworms, they can be clearly identified as they glow when handled, which can be clearly seen at night.