Autumn disease management
Get everything right
When doing presentations, we often say “Greenkeeping is a simple job…all you have to do is get everything right…and all of the time!”. It’s a casual remark, but it seems to chime with people mainly because it’s true. In greenkeeping we have such a large number of tasks to perform (mowing, aeration, vertical cutting, top dressing, fertilising, irrigation etc) in order to create playing surfaces that are able to perform well throughout the year. The trick to successful greenkeeping is to combine all the various operations in such a way that they act together. This requires a great deal of skill, understanding and experience to time everything perfectly to achieve the desired level of playing surface performance.
Autumn disease management is one of the most important phases of work in the greenkeeping calendar. The scars resulting from a damaging attack of Microdochium patch disease inflicted in October might persist through to early spring making the surfaces patchy and uneven for months on end. It is vitally important that we prevent this from happening if the surfaces are going to remain smooth and true. Our recent research work is showing that if we apply an understanding of the factors that might encourage the development of this disease then we can radically reduce the risk of a damaging attack developing. Good news.
Microdochium nivale is a fungal pathogen that can develop quickly and cause widespread damage in a matter of days if conditions are favourable. As an organism it is simply trying to reproduce and it fuels its lifecycle by drawing resources from the turfgrass host. Microdochium patch can be so damaging because it is quick to develop and in doing it has no interest in preserving the health of its host. The disease reproduces at the expense of the turfgrass to cause the scarring that we suffer. An added challenge is that the disease largely goes through its infection and development phases unseen. The symptoms of scarring only appear when the disease has been and done and is moving on with the next generation. It is for these reasons that we need to adopt a preventative attitude towards its control.
The conditions that favour the rapid development of Microdochium patch are generally moist and relatively mild. It needs a susceptible host (Poa annua in particular but all the main turfgrass species are susceptible to varying degrees) and a turfgrass system that is not functioning vigorously enough. We all know that Autumn is the perfect time for the rapid development of Microdochium patch disease. But don’t lose heart because our trials show that we can culturally manipulate the conditions to slow it down. Slowing it down is crucial if we are to keep on top of the situation.
The first thing to “get right” if we are trying to make it difficult for Microdochium patch to develop is to maintain plant health. The traditional advice that we get handed down is that fertiliser is a bad thing at this time of year but this is not entirely true. Underfed or weak turf will jump into disease quicker than turf that is being kept healthy. Too much fertiliser at this time is undoubtedly a bad thing, but no worse than too little. As always, the answer lies somewhere in the middle. As a general rule of thumb, our trial work indicates that if we deliver on average 1-2 kg of N/ha per week while autumn growing conditions are still good then the turf will remain healthy and be slower to develop a microdochium attack. This might be an application of a 4-0-14 fertiliser applied at 30 g/m2 to release its nitrogen over a 4-6 week period in early autumn. The milder winter conditions that have become the norm in recent years also mean that we should think about holding up the turf health during periods of intermittent growth (with an average of 1 kg of N/ha per week). This level of nutrition will help us maintain turf health, colour and quality during this time. The 2 monthly early autumn applications of Greenmaster Pro-Lite “Invigorator Plus” 4-0-14 +8Fe shown in the accompanying graphs show a slower rate of disease development than control plots whilst also maintaining good levels of turf colour and quality.
Autumn fertilisers can also contain sulphate of iron, which can also contribute to slowing down the rate of development of the disease. Our studies have shown that liquid iron sulphate products applied when disease pressure is high can help to slow the development of the disease. In a granular form you may be applying more iron sulphate and so the effect can be stronger and more long-lasting. Pick your products properly at this time.
Leaf moisture is also a key factor to manage in order to limit the rate of development of Microdochium patch disease. Damp turf sat under incessant autumn dews will suffer more disease than dry turf and so morning switching as well as the maintenance of light levels and free airflow with the management of surrounding trees is also important. In our trials we have also shown that the regular application of an effective dew dispersant to reduce the level of moisture sitting in the turf canopy can slow down the rate of development of disease. We have also found that further benefits can be achieved if dew dispersants are used in alternation with penetrant wetting agents. We should note a word of caution, however, because we also saw that the use of dew dispersants might also adversely affect the performance of systemic fungicides and so they should not be used at a time when you need quick uptake of a systemic active ingredient into the turf. It is more important that your fungicide applications are fully effective.
In Autumn 2017 we commissioned an independent trial at the STRI to test these simple understandings within a coherent “ITM” programme where we aimed to deploy a number of different technologies in order to “get everything right”. In this trial we decided to supply granular nutrition with the use of SierraformGT “K STEP” 6-0-27 +2MgO +TE applied at 30 g/m2 (containing slow release nitrogen and potassium). Additional nutrition was applied with monthly applications of Vitalnova “Stressbuster” 7-0-0 +2Fe +sugars +surfactant (40 l/ha) tank mixed with the penetrant wetting agent H2Pro “FlowSmart” (10 l/ha). The dew dispersant H2Pro DewSmart was also applied on a monthly basis to manage canopy moisture. Greenmaster Liquid “Effect Iron” 6.3Fe was applied (30 l/ha) on a single occasion when disease pressure was high. No fungicide was applied to these plots. This is a simple programme but the results in terms of turf colour, quality and the lack of disease speak for itself (see accompanying graphs). The sward was also dominated by Browntop bent and so we really did get everything right! This year we are moving to a Poa annua dominated sward to really put ourselves to the test.
The point of this work is to show you that the practical application of a simple understanding of how to control the factors that favour the development of a disease with the use of focused technologies can really help reduce the speed and damage caused by Microdochium patch in the autumn. If you used these treatments individually they would not have had the powerful effect they showed when used together as part of a programme. This is important because by slowing down the outbreak you will have more time to react and also it will greatly help your fungicide applications to be fully effective and properly control the pathogen. When thinking about your autumn disease control strategy you should try to utilise all the technologies available to keep the greens clean. As we sometimes say “Greenkeeping is a simple job…all you have to do is get everything right…and all of the time”. It might help to think of this as a blessing.