Download Training and development pack on turf diseases for staff

Sports Turf Grass Health and
Protection
Pack 4
Fungal diseases
Pack Code: TGH4
About this pack
Objectives
This pack you will help you to:
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Understand common fungal diseases of turf grass
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Describe life cycles of fungi
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Describe symptoms of fungal infections
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Understand the causes of fungal infections in sports turf surfaces
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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:
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TGH1: Weeds
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TGH2: Pests
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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
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Above fungal mycelium on turf grass
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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.
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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).
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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
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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
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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
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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
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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
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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
.
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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.
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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
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Apply nitrogen fertiliser (assuming the time of year is suitable)
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If required aerate soil to encourage good root growth.
Consider selecting resistance grass cultivars.
Apply a suitable fungicide if the outbreak is severe
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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
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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.
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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
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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.
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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).
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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
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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)
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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?
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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.
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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/
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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
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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
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