Aggressive greenkeeping is the death of the finer grasses


Rust


RUST is a collective term that is commonly used to describe a group of turfgrass diseases, each of which is characterised by the prolific production of small, rust-coloured spores. Where they develop, rust infections can cause a severely detrimental effect to the visual quality of the sward, can reduce the strength of the infected plant making it more susceptible to further infection, and can significantly add to the time spent in cleaning down turfgrass mowers and other mechanical equipment. However, unlike many of the fungi that cause disease on turfgrasses, rust-causing fungi do not directly kill the host plant. Rust diseases are caused by


any one of a number of fungi that need to live on a living host and therefore they only take from the plant what they need to complete their life cycle. In severe


drought stress are more likely to develop rust infections. Leaf wetness is important if the fungus is to infect and therefore extended periods of dew will allow rapid disease development. Following initial infection, the symptoms show as yellow spots or flecks on the leaf and stem. These enlarge and elongate, eventually producing cushions or blisters on the affected plat tissues which, when mature, will split open releasing their spores on to the surface. Warm, damp weather is


outbreaks, this may not appear to be the case but plants invariably recover from even the most severe infection. Different rust causing fungi vary in their life cycles, producing up to five different spore types. All spore types can be produced on the same host plant but many rust- causing fungi complete their life cycle by living for some of their time on an unrelated plant host.


ideal for the development of rust diseases and the damage can be all the more severe on drought-stressed, nutrient limited turf. Management practices include the application of sufficient water and nutrient to avoid either drought or nutrient stress. Reducing the period of leaf wetness will also reduce the development of disease. The mowing height should not be lower than recommended for the grass type and


Some rust causing fungi can cause disease on several grass types whilst others are fairly host specific and different strains or races of the fungi can cause differential infections on specific turfgrass cultivars.


exists between rust causing fungi, it is difficult to provide a general life cycle for them. However, the conditions that tend to favour these diseases are fairly standard. Plants that are showing reduced vigour due to low nutrient input and


Because of the diversity that


infected leaf tissues should be removed after mowing to reduce the inoculum level in the turf. Increased air movement and decreased shading will also minimise the severity of rust infections. As with many turfgrass diseases, the use of a mixed sward will reduce the severity and spread of the disease. Certain fungicides that are currently available for use on managed amenity turf have shown efficacy against these types of turf diseases and, where necessary, can be used as part of an integrated management programme. Always ensure that the disease is correctly identified prior to the application of any plant protection product.


Dr. Kate Entwistle The Turf Disease Centre Tel: 01256 880246


Potassium


Potassium is more mobile and might well need supplementing on sandier soils. Potassium certainly has benefits in terms of drought and disease tolerance but don’t hang all your hopes on it. Monitor potash levels on an annual basis if there is any doubt. Just remember that favouring the finer grasses is all about managing minimal disturbance.


Keep it simple


So, what does this mean in terms of your fertiliser programme? As an example you could kick off growth in spring with an application of lawn sand. This should be applied with the onset of spring growth and will generate recovery from winter wear. An application of 8:0:0 or 8:0:6 fertiliser could then be made when strong spring growth is established. This growth will allow the early season preparations to take place. Using sulphate of ammonia based feeds during the spring will discourage annual meadow grass from invading gaps within the sward by lowering the surface pH. Liquid feeds can then be applied occasionally during the summer months to sustain healthy rather than lush growth. Seaweed soil conditioners may be tank mixed in with liquid feeds if it is felt that they have a beneficial effect. Finish off in the autumn with an application of a turf hardener type product (2-0-2 or 3-0-3 plus Fe or similar) to strengthen growth and harden the sward against disease attack. The rate of applications should be as little as necessary. Your fertiliser programme should be focused on controlling growth so you don't need to employ consistently aggressive surface preparation techniques.


Surface preparations


So, how do we prepare surfaces without incessant verticutting or employing ever-lower heights of cut? Apply heavy top dressings with spring growth to firm and true-up the surfaces. A certain


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amount of verticutting will be necessary at this time but don’t be unduly aggressive or too frequent. Once the surfaces are prepared we should then be aiming to let them be. We maintain our firm, and smooth surfaces without undue growth by brushing, with light in-season top dressings, rolling,


maintaining sensible heights of cut and employing isolated light verticutting if necessary.


Regular top dressing has the added benefit of keeping the turf base sandy and unattractive for annual meadow-grass seed germination.


Less is more


If you want to fertilise for the finer grasses you should be thinking in terms of minimising the need for aggressive surface treatments. You will need strong growth to prepare your surfaces in spring but from then on try to let them go to nature. Your job is to find the minimum growth level possible for you to be able to sustain quality surfaces without incessant verticutting. Ask your fertiliser supplier to concentrate on this when making recommendations based on soil analysis results.


The finer grasses are tender souls that don’t like incessant rough treatment, but they can withstand stress. Remember, at no point do we withhold fertiliser to exert stress. We exert stress on the annual meadow grass for a limited period in summer by controlled droughting in conjunction with overseeding to give new seedlings a chance to take hold. Be patient and stick to your principles and the finer grasses will come.


Get this thought into your head … aggressive greenkeeping is the death of the finer grasses.


Kapeesh? (sic.)


Henry Bechelet is the STRI Turfgrass Agronomist covering North and Eastern England. Henry may be contacted by email at henry.bechelet@stri.co.uk or via www.stri.co.uk


disease OF THE MONTH


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