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Managing turf disease

As winter begins, greenkeepers have to become increasingly vigilant for turf disease problems. In these articles and in my books and on my blog at Bowls Central, you might notice that I have a bit of an obsession with soil health. Over many articles, I’ve described the folly of expecting better results but still doing the same old maintenance on bowling greens (writes John Quinn).

It’s important to find ways to reduce the input of high salt synthetic fertilisers and pesticides in order to create and maintain a healthy rootzone in your green.
The quickest and most permanent way to create a high performance bowling green is to focus on the health of the soil and plants. Even in the very early stages of adopting my Performance Greens Programme, greenkeepers notice a reduction in the incidence of turf diseases, allowing them to significantly reduce and in many cases stop fungicide applications. All because the soil is being allowed to recover its naturally healthy state.
The excessive thatch build up commonly seen on sickly bowls greens is unknown in natural grasslands.
Closely related to this is the almost complete absence in natural grasslands of serious fungal disease outbreaks. The reason for this is that the two (excessive thatch and fungal disease) are cause and effect. Thatch creates the ideal environment for fungal pathogens i.e. a soft, wet and warm substrate populated by weak, sickly plants. Managing turf disease is actually just a matter of understanding this. The reason that we don’t see notable disease outbreaks on natural grasslands and/or healthy greens, is that nature helps plants become disease resistant. And interestingly, we now have the ability to reintroduce and encourage the dominance of many of these natural defences that plants have against diseases in our rootzones. This isn’t a nice to have feature on your green. This is essential for the future of the game as it not only benefits the plants, but it helps to create the right conditions for high performance. And high performance greens beget high performance players. And the cost savings added to this make it essential to club health too.
So what’s not to like about all of that? Why isn’t this the norm?
Two reasons spring to mind: 1. The change isn’t instant, and many clubs are addicted to seeking instant results. Incidentally, although results aren’t instant, they are cumulative, and measurable improvements are experienced all along the way, which I suppose makes it instant-ish! 2. Managing turf disease naturally doesn’t sell stuff quite so effectively or continually as a customer who is constantly lighting fires (applying salt laden, inorganic fertilisers) and then having to put them out again
(with fungicide).
Spongy, soft, thatchy, annual meadow grass turf also moves about continually. This causes a continuum of anomalies on the surface, which can be used to sell sand for top-dressing, which incidentally does nothing to improve the situation and actually adds to the tendency for the rootzone to become inert and lifeless.
In natural grasslands, the grass plants provide the food for the billions of beneficial microbes that live in every ounce of healthy soil. If plants actually suffer and die, this food source is lost to the microbes. Nature, as we’ve belatedly begun to understand, doesn’t need us to help it along, it actually needs us to get out of its way. Over millions of years, the grass plants and microbes have evolved their own systems of co-existence and in the process have developed a range of defence mechanisms to make sure plants stay alive. So, the easiest way for greenkeepers to manage turf well is to exploit these defence mechanisms. First, we must ensure that the grass plants have strong cell walls that are resistant to invasion from fungal pathogens like fusarium and other fungal diseases. To do this we need to prevent too much lush growth by limiting nitrogen application. We can also help this process by applying bio-stimulants which provide plants with many of the elements they need to naturally strengthen the cell walls. It will be no surprise to anyone familiar with the links land, that fescue, with its hard, wiry stricture and similarly robust cell wall structure, is more resistant to disease than annual meadow grass (Poa annua), which is a softer, weaker grass generally, but has a particularly weak cell structure when compared to the hardy perennial grasses. This is down to a greater lignin content in the fescue cell structure, which makes it harder for pathogens to penetrate the cell walls and is more difficult to digest. Given the choice, the pathogen will move on to a softer target like Poa annua, which has more cellulose and high energy sugar in its structure. Knowing this gives you a great advantage in managing turf disease effectively. Fungal pathogens such as Fusarium typically invade plants by exploiting weaknesses, such as physical damage from dull mower blades, through pores or by deploying enzymes to break down the cell wall structure. On natural grasslands like the links land, plants have coexisted and evolved with the diseases that attack them for millions of years. This evolutionary process has helped the plants to develop a range of defence mechanisms that come into play as soon as they come under attack. To counteract such an attack, the grass plant produces its own toxic chemicals and enzymes which fight back against the pathogen. Going a little deeper for a moment, this results in the production of hormones which act much like our own white blood cells do when our body is under attack from disease, injury or infection. These specialised defensive hormones pour into the part of the plant that is being subjected to attack and act as toxins which kill the invading pathogen. Managing turf disease is made simple if we can stimulate the grass to produce these immune responses by using bio-stimulants and keeping off the fungicides.
How soil microbes protect grass plants from disease
Soil microbes employ a variety of key methods to protect our grass plants from pathogens in the soil. They produce toxins. When a grass plant is attacked by a fungal pathogen, it sends out a chemical signal to the surrounding soil microbes, some of which will respond by producing toxins with which to counterattack the pathogen. These work by interrupting the pathogen’s energy supply and are a bit like free natural fungicides, only very targeted and safe to the other soil fungi. They also act immediately, long before there are outward signs of a problem on the turf surface.
Good microbes work to exclude the baddies. I’m often asked: “Can’t we just apply enough fungicide to get rid of the pathogens like fusarium once and for all and then start from scratch building up the beneficial microbe population?” This isn’t how ecology works and in fact, and perhaps surprisingly, many of the plant pathogenic fungi exist in beneficial form in the soil until plants show signs of stress or become weak due to weather, over fertilisation or lose their defence mechanisms for one reason or another. It would be a strange eco-system that nurtured a species whose sole job was to kill plants for the sake of it.It seems then, that potentially pathogenic fungi are opportunists and will turn pathogenic to our plants only when the protective mechanisms supported by beneficial microbes fall down and there’s suddenly a cheap meal available. If you have enough of the good microbes, they will starve the pathogens of food, preventing them from growing, multiplying and continuing the attack so that it never reaches the stage where you’d notice it on the turf surface. This is why it is so important to degrade thatch and convert it to humus by colonising the thatch layer with good fungi and bacteria, because excessive thatch provides the perfect micro-climate and feeding ground for pathogenic fungi like fusarium.

Questions and Comments
You can find a lot more on this subject on John’s blog at Bowls Central. If you have any questions or comments on managing turf disease, please drop him a line to john@bowls-central.co.uk

Caption: Attention to disease prevention and control is important throughout the winter

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