Disease prevention in the autumn and winter

Big picture mentality - Andy and Henry look at how we should go about preventing disease attacks during the autumn and winter period. 

September 1, 2017
7 mins
Dr Andy Owen & Henry Bechelet
ICL Turf & Landscape Technical Managers

Effective disease control though autumn and winter has become more challenging and more essential in recent years. Recent mild autumn and winter weather has created prolonged periods of ideal conditions for the development of fungal disease. This relentless pressure coupled with the ever increasing expectations from players for smooth putting surfaces means that course managers need to work harder than ever to keep their surfaces free from damaging attacks.    

Fungal pathogens infect and feed upon the turf in order to fuel a reproductive life cycle. It is this parasitic feeding, growth and reproduction that causes the damage we see in the form of patches, scars or dieback. We know that the damage these pathogens inflict can persist for months on end to make the putting surfaces pitted and uneven for extended periods.

If the reproductive cycle is left unchecked the spores continue to be produced and dispersed and then they develop, feed and multiply for the disease attack to quickly escalate and cause widespread turf damage.  The diseases that the majority of us are bothered about at this time (Microdochium patch and anthracnose for Poa annua dominated greens) are able develop extremely quickly because of the speed of the reproductive cycle when conditions are ideal.

It is this rapid development and potential for widespread damage that requires us to be proactive with our control measures during periods of high disease pressure. We can’t just sit back and wait.  

Our disease control strategy should involve a number of different tactics… 

  • Manage the environmental conditions to discourage the development of the disease (reduce shading, improve airflow, employ dew dispersion, reduce thatch, relieve soil compaction and installing drainage etc. might all be influential depending on the nature of the disease)  
  • Employ methods that boost plant health to allow it to withstand or recover from attack to help reduce the likelihood of a damaging attack taking hold and developing (optimal nutrition, considerate mowing, maintenance of a clean cut with sharp mower blades for example) 
  • Make applications that directly impede the development of the pathogen (the use of fungistats such as Potassium phosphite or sulphate of Iron).  
  • Focus on actively killing the pathogen with the correct use of fungicide technologies 

So, in essence, we employ our cultural methods and manage the local environmental conditions to reduce the potential for a rapid disease attack, but in a normal year fungicides are also essential if we are to actually control the pathogen population below a level that causes widespread damage.   

The thing about fungicides is that they aren’t all the same.  Some fungicide active ingredients work outside the plant and some work inside. The different fungicide families affect different biochemical processes and work at different stages in the disease life cycle.

These differences mean that it is important to know where and how each fungicide works because if it is not applied at the right time (early enough) then it might be past the stage in the disease life cycle when the active ingredient is effective and so the disease could develop unchecked for a time even though a fungicide has been applied. Some fungicides have multiple active ingredients to broaden the spectrum of attack in order to overcome this issue. It is important to have an understanding of how your fungicides work to ensure effective control.  

One of the key requirements for the successful deployment of most modern fungicides is to apply them preventatively. If the fungicide active ingredient works outside the plant and controls fungal spores (such as the a.i. fludioxinil in MedallionTL and Instrata Elite) then an early application will help to take out the inoculum before it has had a chance to develop and infect the plant.

Disease control is certainly a lot easier without fungal spores. If the fungicide active ingredient works inside the plant (such as the difenoconazole in Instrata Elite) then it needs to be applied early enough to allow it to be taken up by the plant before infection has taken place and provide protection at the point of attack. Fungicide active ingredients that work inside the plant will control pre-existing infections but they don’t magically repair the damage that has already been caused. This is why a preventative approach is always best when using fungicides but you need to know when is best to apply them.   

The problem with taking a truly preventative approach is that the disease can infect the plant and cause significant damage inside the turfgrass host before any visual symptoms begin to show. So it may be that you have treated the greens with a fungicide when the greens seem visually unaffected but the infection has actually taken place and the pathogen is already developing unseen inside the plant. This situation might jeopardise the full effectiveness of the fungicide even if applied just a few days late.

To be truly preventative you will need to use all your experience and knowledge of the conditions that cause disease to develop and anticipate your best opportunity to make a successful preventative fungicide application just before the attack starts running.

Remember that your cultural methods are helping to delay and slow the onset of attack but fungicides are needed to actively control the pathogen when it is starting to grow and feed. The Syngenta fungicide Instrata Elite offers “Outside-In” protection with its 2 active ingredients working against spores outside the plant and providing protection inside, but it still works best when applied at the very early stages of attack. 

To anticipate the risk of infection and make a fully effective preventative fungicide application you need to accurately predict when the pathogen will start to develop. Don’t worry about soothsaying because for a number of years now Syngenta have provided us with weather forecasting and disease prediction models that can be set for your location. These are freely available on the Greencast.co.uk website.  Using Greencast regularly to monitor the predicted disease risk and also identify the spray windows for the upcoming days can really help to get your fungicide timing right.

If you can prevent the attack before it starts (with the control of the spores and/or by conferring internal plant protection) then you stand a way better chance of keeping the greens clean. Fungicides coupled with good cultural management to reduce the speed of regeneration makes for a robust and balanced approach to disease control.   

Don’t forget that the pathogen is only responding to conditions for it to proceed with infection and damage. The increasingly mild and wet weather patterns that we have experienced in recent years create an extremely challenging situation, especially with regard to the development of Microdochium patch during the autumn and winter. We don’t have the luxury of being able to “put the greens to bed” with the advent of hard frosts in October any more.

Last year many courses in the UK and Ireland saw their highest levels of Microdochium patch disease pressure during November, December and January!  You may be hoping that 3 properly programmed fungicide applications with good cultural management will be sufficient to achieve full control, but if disease pressure is high from September to February then you may need to legislate for further applications.  It is a priority for your maintenance plan to get through the winter and into spring intact and so budgets need to be set to accommodate prolonged periods of disease pressure. 

So, successful disease control is essential if we are to maintain the playing quality standards that the golfers now expect. Disease control has undoubtedly become more difficult in recent years due to the milder and wetter weather patterns that have become usual during the autumn and winter. To be successful with your disease management plan, you will need to employ multiple tactics into a coherent integrated disease management plan.

These tactics need to be mapped out into a sequential programme to slow down the development of the disease and control it before it has a chance to cause damage. You will need to be able to react to conditions as they develop and use prediction models to help you keep in front of the situation. Effective fungicide use will require you to deploy the right formulations at the right time. It is important to take a preventative strategy during periods of high disease pressure to keep the greens clean and to ensure that the fungicide actives are working to their optimum. Our team of ICL Area Managers can really help you in this regard because they are specialists in all these technologies.  

Independent research studies have shown that turf managed with fungicides applied preventatively with direct reference to disease prediction models suffered less scarring and fewer fungicide applications were needed compared to a reactive approach.  So, if we have the right attitude to disease control then we can achieve better greens with fewer applications.  Effective disease control these days requires us to have a “big picture mentality”.