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Sports Turf Grass Health and Protection Pack 4 Fungal diseases Pack Code: TGH4 About this pack Objectives This pack you will help you to: • Understand common fungal diseases of turf grass • Describe life cycles of fungi • Describe symptoms of fungal infections • Understand the causes of fungal infections in sports turf surfaces • Understand the control measures available (chemical, physical and cultural) Understand the effects of fungal diseases on sports turf playing surfaces Links to other packs This pack is one in a series about plant health and protection. The full list of packs is: • TGH1: Weeds • TGH2: Pests • TGH3: Turf disorders Introduction to FungiThe Fungi, Kingdom C.80,000 known species including the yeasts, rusts, smuts, mildews, molds, mushrooms and toadstools. Unlike plants fungi cannot make their own food (they are heterotrophic) and obtain nutrients in 3 ways 1. They break down dead organic material (they are one of the organisms able to break down lignum in wood) these are known as saprophytes 2. They kill living organisms and breakdown the tissue (parasitic fungi) 3. They live in a symbiotic partnership with plants aiding the plants grown and in return obtain the nutrients they need to survive (symbiotic fungi) Most plants rely on a symbiotic fungi to help them obtain water and nutrients from the soil. The plants grow specialized roots known as mycorrhizae for the fungi to inhabit. The large surface area of the fungi is able to soak up water and nutrients and then make these available to the plant which in return provides energy-rich sugars manufactured through photosynthesis (a process fungi cannot carry out). Fungi exist primarily as filamentous dikaryotic organisms when conditions are suitable fungi produce spores from which haploid hyphae grow. From these asexual sporangia may develop (these are special hyphae which produce spores). Many fungi reproduce sexually when haploid hyphae from 2 fungal organisms meet and fuse. However some fungi reproduce by asexual spores or by vegetative growth only. Other fungi reproduce by asexual fission or fragmentation i.e. the organism breaks apart and each part continues to form a new organism. Fungal spores can remain inactive in the environment for extremely long periods and become active again when conditions are suitable. This fact makes the control of fungal diseases extremely hard i.e. they is always a large deposit of potential agents of infection present (in the soil, plant debris etc). Fungi are vital to the environment as they breakdown organic matter releasing its nutrients for other organisms. However they also have the potential to be extremely destructive. Fungi are also able to produce sclerotia, these are in as sense like a seeds produced by plants in that they enable the fungi to ride out periods of stress and then emerge again when conditions are suitable. Sclerotia develop from a knot of hyphae which shortens and become tightly packed developing think walls able to withstand adverse environmental conditions. These sclerotia can rest up in dead or living plant tissue as well as the soil for long periods. When conditions improve germination may result in the emergence of hyphae or in some species by the production of fruiting bodes that produce spores. Mycelium is the term used to describe the vegetative part of the fungus and comprised of a mass of hyphae. Above Sclerotia on turf grass Turf grass health Above fungal mycelium on turf grass 2 Factors leading to out breaks of fungal diseases Environmental factors Any factor that inhibits/weakens grass or results in unnatural growth can lead to an increase in turf grass diseases. Moisture Fungi can spread easily in the presence of water, however they are mostly inhibited by dry conditions and this is one of the main reasons for the switching or brushing of dew carried out by Greenkeepers in the mornings. Poor drainage will also increase moisture levels around the grass plant as will excessive irrigation. Therefore good drainage via well maintained drains and aeration and irrigation practices are vital. In addition extended periods of drought can severely stress turf grass leaving them vulnerable to diseases when the conditions become wetter. Light Shade can reduce the ability of the turf grass plant to manufacture suitable levels of food reserves via the process of photosynthesis. This weakens the grass leaving it open to attack by disease. Removal of overhanging branches, thinning of trees can help increase light levels. Air movement Areas that are sheltered will be slow to dry out and therefore have increased moisture levels which aid the spread of fungal diseases. Nutrients Lack of suitable food will lead to poor health in all organisms including turf grasses. The application of correct nutrients is vital to ensuring turf grass can survive and recover from attacks as well as help avoid them in the first place. In addition excessive nutrients can lead to lush leaf growth that is easily attacked by fungi. In particular high rates of nitrogen in the autumn are associated with a high risk of fursarium disease. Soil pH The pH of a soil (how acid or alkaline it is) can play a key role in the management of turf grass diseases as it dictates the availability of nutrients in the soil to the grass plant. The idea soil pH is between 5 and 6.5. In addition soil pH can affect the development of some fungal species. Soil condition The condition of the soil is important as most of the grass plant grows below the soil. Compacted soils will inhibit root growth and therefore a plants ability to obtain nutrients. Also compacted soil will not drain well leading to increased moisture levels around the plant. Poorly drained soil will also be low in oxygen which will prevent healthy plant growth. Temperature Some diseases become inactive in very hot or cold conditions and are stimulated by the right temperatures. Although little can be done to control temperature it is a factor that can help evaluate when an attack is likely. Soil temperature can be affected by the drainage of the soil i.e. poorly draining root zones will contain large qualities of water and so will cool slowly in the autumn meaning grass growth may continue later into the year leading to young lush leaves that might be attached. Therefore good drainage and aeration practices are important in combating diseases. Turf grass health 3 Chemical controls A turf grass disease is controlled using a Fungicide. There are various types of fungicides Preventative These are fungicides that are designed to be used before an attack and you can think of it as being like getting a flu jab. When you get a flu jab from the doctor it protects you from the flu. Preventative fungicides might be systemic or contact in action (see below). Curative These are fungicides that are designed to be used after a fungal attack has began, you can think of it as being like getting some medicine from the doctor when you are ill. Contact A contact fungicide would coat the grass plant, killing any fungi active on the surface of the grass leaf and help protect the plant from attack for a period of time. As a contact will be removed by cutting they are often best used during periods of slow growth. Systemic These get into the plant and work from within. They move around the plants “system”. A systemic fungicide would enter the grass plant and kill any disease present and protect it from attack for a period of time. These are best used during periods of active growth. Below- How contact and system chemicals protect grasses Below- Diagram showing fungal spores attacking the grass plant in various ways. Fig. 2. A microscopic view of plant infection by spores of various fungi. Some fungi can infect plant tissue through unwounded surfaces i.e. they can penetrate the cell surface directly (A and B). Sometimes, fungi can infect the plant through wounds (C) wounds are common i.e. cut leaf after mowing or damage from players feet. They can also enter a plant through natural microscopic pores in the plant leaves call stoma (D). Turf grass health 4 The most common turf grass diseases in the UK 1. Antracnose (Colletotrichum cereale (formerly Colletotrichum graminicola) Anthracnose attacks grass plants (mainly Poa annua) that are under environmental stress i.e. low nutrition, poor surface drainage and compacted soils etc. This disease can cause wide areas of damage. Once the disease reaches basal rot stage fungicides are no longer effective in curing affected plants but should be applied to prevent further attack and damage. Therefore early diagnoses of the problem is vital in keeping damage to a minimum. Signs and symptoms Yellowing of the leaves and thinning of the turf surface Basal rot of the grass plant and (under a magnifying glass) black needles embedded in the grass leaf Life cycle Becomes active and disease develops, foliar lesions develop releasing conidia Conidia are transferred to nearby plants by rainfall, surface moisture Infected leaf tissue Overwinters as mycelium or stromata Control measures Turf grass health Ensure nutrient levels in the soil are at a suitable level Avoid very low heights of cut Try to ensure good surface drainage through aeration and sand top dressings in the growing season Try to reduce the amount of Poa annua in the sward (overseed with bent/fescue) Remove morning dews to keep plants dry Try to ensure good light levels and air movement over surface Apply a suitable fungicide to protect vulnerable areas 5 2. Dollar spot (Sclerotinia homoeocarpa) This disease mainly affects fescue species of turf grass. It is caused by low nitrogen levels and high level of leaf surface moisture in temperatures of 21-26C Signs and symptoms Signs and symptoms include: Distinct straw coloured sunken Spots 2550mm in diameter. The leaf lesions have a bleached centre and reddish brown borders. The leaf tip may remain green while the lesion extends across the blade. White mycelium covering the infected area may be visible especially in the morning dew Life cycle Survives in dead leaf tissue in the thatch layer compact masses of mycelium called sclerotia The fungus enters susceptible plants through stomates, leaf tips that have recently been mown, and by direct penetration of intact leaf tissue Plant to plant spread occurs via hypha extension from one leaf blade to adjacent leaves Control measures Turf grass health Reduce periods of leaf moisture (remove dew) Aerate to ensure that rootzone is not compacted. Try to reduce high thatch levels by scarification etc. Remove cuttings from affected areas if possible. Ensure nutrient levels in the soil are at a suitable level to help avoid the problem and aid recovery if it occurs Try to ensure good light levels and air movement over surface Apply a suitable fungicide 6 3. Fursarium patch (Microdochium nivale) Signs and symptoms include: Circular patches that can grow up to 300mm in diameter. These areas become water soaked, and the leaves turn reddish-brown and then bleach. Pink mycelium may be visible in early morning dew (looks like cob webs). Also a dark “halo” can sometimes be seen and the dew does not form uniformly over the affected areas. The disease develops under wet, humid, cool (0-15 degrees Celsius) condition. High nitrogen levels in the autumn and excessive thatch are also major contributors. Life cycle Dormant periods are spent in thatch (dead leaf material) or the soil as haploid mycelium or spores. As autumn arrives the dormant structures form mycelium grows and invades plant tissue. These conditions also favor the development of asexual spores called conidia on conidiophores. These infect leaf sheaths and blades near the soil. Surface water and the movement of players and machinery will help spread of this disease as they transfer spores to nearby healthy plants. Control measures Do not apply excessive amounts of nitrogen in late summer/autumn period In autumn use fertilizers with a high K to boast plant resistance Applications of iron can acidify the leaf surface inhibiting development of the disease Ensure dew is removed in the mornings Ensure thatch levels are managed Ensure good surface drainage Ensure good air flow and light levels on the surface Use acidifying fertilisers to get pH below 7 Apply a suitable fungicide as soon as symptoms appear. If the area is a high risk a preventative fungicide before an outbreak should be considered . Turf grass health 7 4. Red thread and Pink patch (Laetisaria fuciformis and Limonomyces Roseipellis) Red Thread and Pink Patch are diseases that occur mainly on turf with low levels of nitrogen Compacted soils or poor rooting can increase disease occurrence as this restricts the plants ability to extract the nutrient it needs to prevent this disease. Pink patch Red thread Signs and symptoms Light brown spots can be seen on turf, these may not form distinct shapes. The affected areas will have a straw coloured leaves and reddish tinge to the affected areas. Red mycelial growth may extend out from lesions in leaf (hence its name red thread). In the case of Pink patch, pink clumps of mycelium may be seen on the leaves. Life cycle Over-winters as dried gelatinous mycelium on infected dead leaves until suitable conditions Fungi enter leaves through natural openings and cut tips of leaves to infect the entire plant Mycelium becomes active Mycelium is spread by movement of players etc to infect new plants Control measures Apply nitrogen fertiliser (assuming the time of year is suitable) If required aerate soil to encourage good root growth. Consider selecting resistance grass cultivars. Apply a suitable fungicide if the outbreak is severe Turf grass health 8 5. Grey snow mould (Typhula incarnata) Grey snow mould is most severe when the temperature of the turf surface close to freezing for extended periods. Heavy snow fall on unfrozen ground or accumulations of leaves may provide ideal conditions for disease development i.e. the wet surface below the snow and isolating cover provide conditions suitable for the rapid development of the disease. Heavy applications of nitrogen, longer than normal grass height of cut going into the autumn can provide soft vegetation for the pathogen to attack. Signs and symptoms Grey coloured patches on the turf (mostly appearing as snow melts) Mycelium may be present on the affected areas. Life cycle Grey snow mould pathogens survive the summer as sclerotia in the thatch and soil. Sclerotia germinate in the autumn l when temperatures are between 10 C (50°F) and 18 C (65°F). These germinating sclertia produce spores and mycelium that continue the infection to new areas Control measures Ensure good surface drainage Control thatch levels Frequently remove leaves and other debris from turf surfaces during autumn and winter Do not apply readily available nitrogen fertilisers in the autumn period If prolonged snow cover is expected if possible ensure turf is cut prior to the snowfall and consider a preventative fungicide application. Turf grass health 9 6. Take All Patch (Gaeumannomyces graminis / Ophiobolus) Take-All Patch is most commonly found on newly constructed sand based greens. It is a disease that tends to reduce over time. It is possible that new build greens do not have the range of natural organisms tat normally compete with and keep the pathogen in check. Therefore overtime Take-all is likely to reduce due to build-up of natural antagonists whereby the diseases become less severe. Sudden changes of soil pH e.g. by applications of lime to raise soil pH can also activate the disease. Soils with low CEC, poor nitrogen fertility and with a high pH (>6.5) are also suitable conditions for outbreaks Take-All Patch primarily attacks Bent (Agrostis) grasses and therefore overseeding with fescue species can help cover the damage. Signs and symptoms Circular patches/rings are created where the Agrostis species have been killed off allowing invasion of weeds species. Life cycle Take-all survives in the soil on infected grass residues. When conditions are suitable the fungus on these residues infects the root tissue of young plants. Take-all can also form hyphae which spread the disease through the soil between plants, and for this reason the disease is often seen in patches. Control measures Ensure good availability of nutrients in poor nutrient holding soils. Try to reduce pH of soil so that conditions are less favourable to pathogen. Increase biological activity in the new sand environment so that there are more natural antagonists to the pathogen. Manganese (Mn) has be shown to be effective as part of an integrated approach. Check water quality for pH and nutrient levels. Use acidifying fertilisers. Avoid organic fertilisers, which tend to increase pH. Avoid potassium nitrate, which increases soil surface pH. Check topdressing pH. Use fungicides as part of an IPM programme and be aware of causing resistance to one chemical group by its regular use. Turf grass health 10 Fairy rings The 3 main types of Fairy ring: Signs and symptoms Type 1: Marasmius oreades – A ring of dead turf bordered by stimulated areas of grass growth. The cause turf death is the water repellence and/or toxic substances generated by the fungi in the affected area. The mycelium causes the soil to be hydrophobic and the grass suffers from drought stress. In addition some toxins are produced by the fungi that speed the death of the weakened grass. The dead grass material is then consumed by the fungi and nutrients are released. It is the release of these nutrients that cause the rapid lush growth on either side of the dead ring of grass. Type 2: Agaricus & Lycoperdon spp – These stimulated grass growth with no fungal bodies. They rarely causes excessive damage to turf, with the main issue being they are unsightly and due to the differing growth rates of turf in the affected areas can interfere with play on fine turf surfaces such as golf greens. Type 3: Hygrophorus & Psilocybe spp - no damage to the turf grass except nuisance when fruiting bodies are present (in autumn). Turf grass health 11 Life cycle Varies dependent on disease present Fairy rings can be spread by spores or by vegetative means. In the case of type one the fungi moves from the soil breaking down organic tissue. When conditions are suitable fruiting bodies may appear which produce spores that area spared by the wind or movement by players etc on the surface and these can create rings in a new location. Control measures Minimise conditions which favour disease development e.g. by control thatch levels. Apply wetting agents that have a penetrant activity will help to move water through the hydrophobic layer to help cure the symptoms of the disease, this should be done in combination with deep aeration. If aeration is used ensure the equipment is sterilized afterwards to prevent spread to other areas Nitrogen fertilisers can be used to help mask the visual symptoms of light and dark green rings. Where required use an approved fungicide in combination with a wetting agent to maximise the ability of the fungicide to reach the affected areas (note fungicide treatment is problematic and not certain in its results) Turf grass health 12 Activity -Quiz – to check your understanding of turf grass diseases Answer the following questions: 1. Identify the following fungal diseases: a) b) c) d) 2. State the most likely time of the year for out breaks of fusarium 3. Red thread disease can be mainly prevented by applications of which nutrient? 4. State 2 ways in which fungal diseases can spread 5. Explain why extremely high or low soil pH may make grasses more vulnerable to disease 6. State the difference between a contact and systemic fungicide 7. When is a preventative fungicide best used? Turf grass health 13 8. What is the connection between high moisture levels and disease outbreaks? 9. If fungi require moisture to establish (i.e. for the germinating spore to survive) how can Greenkeepers help prevent moisture? 10. Some fungi can enter via through wounds in the grass leaf, what might be the causes of these wounds and is there any way in which Greenkeepers can help lesson plant wounds? Check your answers with those at the end of the pack. Turf grass health 14 Acknowledgements Some images used are from the world’s leading sports turf consultancy the STRI http://www.stri.co.uk/ Further reading http://www.syngentacropprotection.com/assets/assetlibrary/Syngenta_DiseaseID_Guide.pdf http://www.bali.org.uk/quality_assurance/advice/420 http://www.escience.bayercropscience.co.uk/bcsweb/es/bcs_uk_greenws.nsf/id/UK_Turf_Disea ses http://www.rolawn.co.uk/turf-disease-and-insects Glossary of terms A great glossary of fungi terms can be found at http://fungiforthepeople.org/mushroom-info/mycoglossary/ Turf grass health 15 Answers to activities Activity -Quiz – to check your understanding of turf grass diseases Answer the following questions: 1. Identify the following fungal diseases: a) Fusarium c) Red Thread b) Take All d) Dollar spot 2. State the most likely time of the year for out breaks of fusarium Autumn 3. Red thread disease can be mainly prevented by applications of which nutrient? Nitrogen 4. State 2 ways in which fungal diseases can spread Spores and vegitatively (mycelium) 5. Explain why extremely high or low soil pH may make grasses more vulnerable to disease Affects nutrient availability and hence growth of plant 6. State the difference between a contact and systemic fungicide Contact stays outside of the plant, systemic enters the plant 7. When is a preventative fungicide best used? Prior to an outbreak of disease i.e. when conditions are suitable and an outbreak is a high risk Turf grass health 16 8. What is the connection between high moisture levels and disease outbreaks? Fungi can only spread effectively in the presence of moisture 9. If fungi require moisture to establish (i.e. for the germinating spore to survive) how can Greenkeepers help prevent moisture? Remove dew in mornings, try to ensure good drainage, careful irrigation and ensuring good levels of light and air over surface to keep it dry 10. Some fungi can enter via through wounds in the grass leaf, what might be the causes of these wounds and is there any way in which Greenkeepers can help lesson plant wounds? Try to use sharp well set mowers Turf grass health 17