Three major factors contribute to the development of a plant disease: a susceptible host, a virulent pathogen and a favourable environment - the disease triangle
smuts and slime moulds. Diseases can often be difficult to
control. Most IPM strategies work very well and often involve the use of fungicide treatments to help suppress potential outbreaks of disease. As a general rule, fungicide applications should be made during the first signs of attack, since disease can cause substantial damage in a short period of time. In recent years there has been a decline in the use of fungicides. Recent studies have shown that constant use of fungicides often sees the disease becoming resistant to them. There are many types of fungicides available and manufactured for use on amenity turf situations, all designed to perform and act differently. Systemic fungicides (azoxystrobin, trifloxystrobin, propiconazole, tebuconazole, prochloraz, thiophanate-methyl and carbendazim) all belong to three groups of fungicides - the strobilurins, the triazoles and the benzimidazoles. All have differing modes of action and should be used in sequence to avoid sensitising the fungal pathogens to them and avoid the potential of resistance. They have varying levels of systemicity. Non-systemic fungicides are
contact acting, such as iprodione and chlorothalonil. They also have protectant activity. A complete list of available chemicals registered for use on amenity grass situations can be seen in the The UK Pesticide Guide 2008. The main management tool for
controlling pests and diseases is, by definition, an Integrated Pest Management strategy (IPM) that comprises a number of tasks and checks providing a comprehensive approach to controlling insects, weeds and pathogens in an economically and environmentally sensitive way, using cultural bipological and chemical management tools to reduce the incidence of infection in managed turf. The disease triangle is a concept of plant pathology and is based on the principle that disease is the result of an interaction between a host, a potential pathogen and the environment or weather conditions. Plant disease is prevented by elimination of any one of these three causal components. Keeping the sward healthy and
reducing the conditions that favour disease will be the first priority to keep disease from your turf. The following actions should help you achieve this:
Environment
Disease Pathogen Host
• Carry out programmes of aeration to help keep the surface free draining.
• Inspect and monitor existing surface water drainage systems; ensure that they are working.
• Prevent moist conditions remaining on the surface by
brushing/sweeping/switching the playing surface (remove dew).
• Apply a balanced fertiliser to keep the sward healthy. A soil analysis will identify fertiliser requirements.
• Control thatch layers as thatch provides a good environment for the disease outbreaks. Reduce thatch by hollow coring and scarification.
• Reduce the return of clippings. An accumulation of dead matter will increase thatch.
• Maintain Soil pH between 5.8-6.5; do not allow the soil to become alkaline.
Leaf Spot/Melting Out
Drechlera spp, Bipolaris spp and Curvularia spp Symptoms and conditions
Very common disease in the UK. The disease is seen as streaks and patches of affected grasses, the disease is most prevalent under warm, moist, humid conditions. The disease spores are spread by water splash from rainfall and irrigation.
Control
Some grasses are more susceptible than others, use more resistant varieties. Keep the sward healthy, implement a IPM strategy.
Fungicide - carbendazim + iprodione, azoxystrobin, tebuconazole, propiconazole
Powdery Mildew Erysiphe graminis Symptoms and conditions
Usually seen in late spring especially after prolonged dry weather, leaves appear white or pale grey. If left unchecked a heavy infection will result in the sward thinning. Smooth stalked, perennial rye and fescue grasses are most affected. Affects grasses grown in the shade and with poor air circulation.
Control
Improve air circulation and reduce shade. Implement a IPM strategy. This is an uncommon disease in turfgrass, and product labels may not have specific recommendations.
Fungicide - iprodione, azoxystrobin, chlorothalonil, tebuconazole
Red Thread Laetisaria fuciformis Symptoms and conditions
Usually seen in summer and autumn months, the disease appears as patches of damaged grass having a pink to red tinges (red needles of the fungus).
Control
This disease is associated with infertile soils. Effective soil management and correct feeding programmes coupled with a IPM strategy will help combat this disease.
Fungicide - iprodione, chlorothalonil
Take all Patch
Gaeumannomyces graminis, forerlly Ophiobolus graminis (Ophiobolus patch)
Symptoms and conditions
This disease appears during the summer, and seen as saucer shaped, depressed areas of infected bent grasses that appear bronze in colour. 0.3m in diameter. This disease affects all bent grasses.
Control
Keep soil pH level consistent. A sudden rise in soil pH can see a severe attack of take all patch. Ensure a good IPM strategy is in place.
Fungicide - azoxystrobin
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