Autumn disease control

As the summer comes to an end, the focus of our greenkeeping practice changes and our thoughts turn to preparing for the following year.  Autumn is generally a time of renovation when we try to bring about improvements in the quality of the grass cover or the nature of the soil profile that will hopefully stand us in good steads for the following year.  Autumn is the time when we try to shape the future. 

Autumn can also be a time of jeopardy with disease pressure and moisture levels potentially exerting a negative influence on the turf qualities to affect the performance of the greens through the upcoming winter, spring and early summer.  What happens in the autumn can have a major influence on golfer’s satisfaction and damaged or unhealthy turf can set an uneasy tone for months on end.  Autumn disease control on our greens is one of the key disciplines of the modern greenkeeper if we are to produce good playing surfaces throughout the year and keep everyone happy. 

At ICL we value trial work.  We invest in independent and internal trial work to help us innovate and produce the best technologies. We also conduct product testing to help us provide the best advice for our customers, and because we find it interesting and also because it stimulates a progressive and positive outlook towards turf maintenance.  Last year we commissioned a trial to investigate a few interesting questions regarding fine turf disease control in the autumn.  We hope that the findings help provoke you to put together a better disease control plan for this autumn. 

The objectives of the 2015 ICL Autumn Disease Control Trial were three-fold… 

1. Evaluate if an H2Pro DewSmart dew dispersal programme helped reduce the incidence of Microdochium patch on fine turf 

1. Evaluate whether H2Pro DewSmart dew dispersant when used in combination with fungicides enhanced or inhibited the effectiveness of the treatments 

1. Evaluate the potential of Greenmaster Liquid Effect Fe (applied preventatively or curatively) to reduce the incidence of Microdochium patch on fine turf.     

The trial was conducted at the STRI through the autumn of 2015.  It was set up as a randomised and replicated complete block design with 14 treatment combinations (including an untreated control).  The trial was set upon an area of indigenous sandy loam soil with the sward composition being a blend of Annual meadow grass (Poa annua) and Browntop bent (Agrostis capillaris).  The site was managed to maintain a high disease pressure, and to encourage Michrodochium outbreaks.  The key results are described below.  

1. Using a quality dew dispersant in a programmed approach can significantly reduce disease outbreaks. 

DewSmart dew dispersant was applied every 14 days at 10 L/ha  in 250 L water.  Application was made to a dry leaf where possible (both switched and air dried).  The programme of DewSmart applications was shown to significantly reduce the incidence of Microdochium disease on the turf (Figure 1).  It did not prevent the outbreak completely but it clearly had a positive effect and shows one of the benefits of dew suppression.  

Figure 1:  Area of plot affected by Microdochium : DewSmart vs Control. (* indicates significance) 

1. Dew dispersants and some fungicides are compatible – but care is needed 

We often get asked if the application of dew dispersant could adversely affect the performance of other treatments such as autumn fungicides.  So, to investigate this H2Pro DewSmart was either applied tank-mixed with the contact fungicide Medallion TL from Syngenta (a.i. fludioxonil) or applied 2 hours after Medallion TL.  In both cases the efficacy of the fungicide was not adversely affected.   In both cases Medallion effectively controlled disease incidence. 

DewSmart was also applied tank-mixed with the systemic fungicide Banner Maxx from Syngenta (a.i. propiconazole (this product is no longer available) as well as being applied 2 hours after Banner Maxx.  In both cases the efficacy of the fungicide was reduced.  When tank mixed with the H2Pro DewSmart the efficacy of Banner Maxx  was significantly reduced (Figure 2).  Also for the staggered application, the efficacy of the fungicide treatment was reduced (but not significantly) compared with straight Banner Maxx application.  The Banner Maxx application without any associated dew dispersant effectively controlled disease incidence. 

Figure 2:  Area of plot affected by Microdochium : DewSmart and Fungicide Interaction. 

DewSmart was applied 2 hours after Instrata from Syngenta (a.i. chlorothalonil, fludioxonil and propiconazole). DewSmart and Instrata are not tank mix compatible.  In this case the efficacy of the fungicide was not significantly affected. In all cases Instrata effectively controlled disease incidence. 

So, no benefit was demonstrated by combining DewSmart with a fungicide.  For Instrata and Medallion there was no negative impact associated with their use in conjunction with DewSmart but when it was used with Banner Maxx, the effectiveness of the fungicide treatment was adversely affected. 

1. When applied curatively Greenmaster Effect Fe significantly reduced the disease outbreak and development 

Greenmaster Liquid Effect Fe (a specially formulated mix of complexed and chelated Iron) had been previously shown to have an apparent fungistatic effect against Microdochium Patch disease in a laboratory study.   This characteristic was tested in this trial as a potential preventative ITM measure to reduce the risk of Microdochium Patch disease developing in the field.   The Greenmaster Liquid Effect Fe was either applied preventatively at 28 day intervals or curatively at the first sign of disease (both at a rate of 30 L/ha in 400L water).  This study showed that applying Effect Fe curatively at the first sign of disease significantly reduced the disease development and outbreak (Figure 3).  However the disease levels sustained would not be considered acceptable for fine turf management.   Applying Effect Iron preventatively (as a “turf hardener”) did not reduce disease incidence or severity. 

Figure 3:  Area of plot affected by Microdochium : Effect Iron vs Control. (* indicates significance) 

Control Plot

DewSmart Programme

Effect Iron

Medallion

OVERALL CONCLUSIONS AND RECOMMENDATIONS 

It is crucial during the autumn months to minimise disease incidence on our fine turf surfaces.  This study showed that there are significant benefits to be had from suppressing dew formation with H2Pro DewSmart and treating emerging Microdochium attacks with Greenmaster Liquid Effect Fe but these methods should only be considered as a part of your ITM programme.  This study also served to confirm the overwhelming benefits of using premium formulated fungicides applied preventatively when trying to achieve full disease control.  The study showed that the use of DewSmart did not adversely affect the performance of Medallion TL and Instrata but it did reduce the effectiveness of Banner Maxx, which is an important consideration if we are looking to maximise the effectiveness of those fungicide treatments.   

As with all disease control plans it is important that we consider all the influence the development and severity of the outbreaks (light, shade, thatch, grass types, plant health etc. etc. etc.).  We hope that in this simple study we have helped you with your thinking about a few possible additional elements to this year’s plan.  We would say to use DewSmart and Effect Fe as part of your plan but if you need complete control then the preventative use of premium fungicide technology is also vitally important.  With this information we hope to have helped you shape the future in a positive, proactive and integrated way.