Disease process
 Disease monitoring techniques and...
 Cultural control practices
 Mowing practices
 Nutrition management
 Soil physical and chemical...
 When to use a fungicide
 Contact fungicides
 Local-penetrant fungicides
 Read labels
 Table 1: Turfgrass fungicies listed...
 Table 2: Common name and chemical...
 Figure 3: Dry patches in St. Augustine...

Group Title: Plant protection pointers/Extension plant pathology reports
Title: Turfgrass disease management
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066909/00001
 Material Information
Title: Turfgrass disease management
Series Title: Extension Plant Pathology Report 64
Alternate Title: Plant Protection Pointers
Physical Description: Book
Language: English
Creator: Elliot, Monica L.
Simone, Gary W.
Affiliation: University of Florida -- Florida Cooperative Extension Service -- Plant Pathology Department -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 2001
Spatial Coverage: North America -- United States of America -- Florida
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066909
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
        Page 1
    Disease process
        Page 2
    Disease monitoring techniques and symptoms
        Page 3
    Cultural control practices
        Page 4
    Mowing practices
        Page 5
    Nutrition management
        Page 6
    Soil physical and chemical status
        Page 7
    When to use a fungicide
        Page 8
    Contact fungicides
        Page 9
    Local-penetrant fungicides
        Page 10
    Read labels
        Page 11
        Page 12
    Table 1: Turfgrass fungicies listed by chemical class
        Page 13
    Table 2: Common name and chemical name of turfgrass fungicides
        Page 14
    Figure 3: Dry patches in St. Augustine grass- no disease
        Page 15
Full Text

University of Florida

Plant Protection Pointers

Extension Plant Pathology Report No. 64

Turfgrass Disease Management

Monica L Elliott and Gary W. Simone
Associate Professor, Ft. Lauderdale Research and Education Center, University of
Florida, 3205 College Ave, Ft. Lauderdale, Fl 33314 and Professor (Emeritus),
Plant Pathology Department, University of Florida, Gainesville, Florida 32611.
Revised April 2001


Turfgrass diseases are difficult to understand because the biological organisms (plant
pathogens) causing the problems are rarely observed. Fortunately, grasses maintained using
proper cultural practices (water, mowing, fertility) are not as likely to become diseased or be as
severely damaged as grasses not receiving proper care. The following section discusses turfgrass
diseases, their causal agents, diagnosis and management.

What is a disease?

Observing spots and patches of yellow or brown turfgrass does not automatically mean
the turfgrass has a disease. While turfgrass injuries or disorders may look like diseases, they are
not diseases and should be treated differently. Because diseases are difficult to diagnose, it is
often faster to rule out involvement of other factors than to verify the presence of disease. Dis-
eases are the exception and not the rule for most turfgrass plantings. By determining if other
factors are causing the turf to look sick, you will solve the problem more quickly and avoid
applying unnecessary fungicides.


An injury to turfgrass is a destructive physical occurrence such as pesticide damage (Fig-
ure 1), mowing the grass too short (Figure 2) or a fuel leak. A turfgrass disorder is an interaction
between the plant and its environment that is usually associated with imbalances of physical or
chemical requirements for turfgrass growth. Examples would be nutritional deficiencies, cold
stress, drought (Figure 3) or excessive rainfall. Again, while these problems may appear to be
diseases, there are no pathogens involved. However, these injuries or disorders may weaken
the turf so much that a pathogen may attack the plants and cause a disease.

A disease is an interaction between the plant and a pathogen that disrupts the normal
growth and appearance of the plant. It consists of three components: host, pathogen and the
conducive environment in which the host and pathogen interact. The environment is the key
factor for disease development since the turfgrass host and turfgrass pathogens are naturally
always present. While diseases may affect turfgrasses all year, individual turf diseases are
active for only a few months each year, usually due to weather patterns and the resulting envi-
ronmental effects. However, any stress (environmental or man-made) placed on turf will weaken
the turf, and thus make it more susceptible to disease development.

Except for one disease caused by a virus, turfgrass diseases in Florida are caused by
fungi. Examples of fungi in your daily life include the molds in the bathroom or refrigerator, the
green stuff on an old orange or bread, and the mushrooms you eat. Unlike plants, fungi are
unable to produce their own energy and must rely on living or dead hosts for energy and growth.
Most fungi living in the turfgrass environment are totally harmless, using only dead organic
matter (such as thatch) for growth. A very limited number of fungi, at some point in their life
cycle, cause plant diseases by infecting living plants.

It is important to know that when a fungal pathogen is not actively attacking the plant, it
has not disappeared from the turfgrass area. It is simply surviving in the environment in a state
of dormancy (like a bear in hibernation) or as a saprophyte (non-pathogenic phase) living off
dead organic matter in the thatch and soil layers.

The one viral disease, centipedegrass mosaic or St. Augustinegrass decline, in not
observed very frequently in Florida. The St. Augustinegrass cultivars commonly used are resis-
tant to the virus. In centipedegrass, the virus alone does not cause decline and death, but it does
add another stress factor to the turfgrass.

Disease process

There are many steps in the disease process, and all are dependent on environmental
conditions. The first step is inoculation, when the pathogen comes in contact with the suscep-
tible plant. For turfgrass, this is always occurring. It is the next steps that will determine if a
disease will develop. In the second step, the pathogen must actually enter the plant. This is
called infection. Fungi can enter a plant via wounds (cut leaf blades), natural openings stomatess),
or they can penetrate directly using a number of different mechanisms. Just because a fungus
enters/infects a plant does not mean a disease automatically develops. In the next step, the

pathogen must become established inside the host. It is at this point that the pathogen will start
to disrupt the normal growth of the plant or affect the appearance of the plant. Depending on the
pathogen, it may then reproduce (example: produce spores). These reproductive structures or
other parts of a pathogen may then spread to other turfgrass plants. A disease epidemic means
that large populations of turfgrass plants are affected by the pathogen.

Disease monitoring techniques and symptoms

Unlike insects or weeds, it is not possible to monitor the number of turfgrass pathogens
present in a given area. Instead, one monitors disease symptoms (if already present), the weather,
and the stress factors affecting the turfgrass. It is critical to document active disease sites, as
many disease outbreaks will occur in the same location each year. Use these records to deter-
mine why the disease is occurring in those locations (shade, fertility, soil type), to help predict
disease outbreaks, and to design effective management strategies.

There are two common patterns of turfgrass disease symptoms. One is a circular patch of
turfgrass, either small or large, that is no longer uniformly green. The second is turf that has
'spots' on the leaves. For disease patches, examine the leaves and roots in these patches for
characteristic symptoms of a disease and signs (actual fungal structures) of the pathogen. (See
key and description of individual diseases that follows.) The best time to observe fungal myce-
lia is in the early morning when dew is still present. Early afternoon is a good time to look for
localized patches of wilt or drought symptoms that may indicate root or crown diseases. For
turf with spots, note the color and shape of the spots.

Monitoring the weather will help with disease prediction and with determining the ne-
cessity of fungicide applications. If the disease affected areas are small and the weather is not
conducive for an epidemic, then a fungicide may not be necessary or only spot applications will
be required. However, if the long-term weather forecast is conducive for disease development
of a disease that routinely occurs in your area in specific landscapes, then a fungicide may be
useful to prevent a disease outbreak. Also take note of the location in the landscape where the
disease occurs, especially if it occurs more than once in a year or recurs each year. The disease
may be occurring in areas affected by a microclimate created by man.

Disease control is not simple or easy!

Since it is usually not practical or desirable to eliminate the turfgrass host, disease control
recommendations are aimed at: 1) altering the environment so it is less favorable for disease
development, 2) suppressing growth of the pathogen, and 3) decreasing stress on turfgrass. An
integrated management program that includes cultural and chemical methods is the key to pre-
venting and controlling turfgrass diseases.

There are three steps to disease management. First, correctly identify the disease. Sec-
ond, identify the conditions promoting infection and disease development. Third, identify the
management techniques that will alter or eliminate these conducive conditions.

For landscape maintenance companies and pest control companies, the primary obstacle
they may face is lack of control over ALL the management practices. For example, the home-
owner may control the irrigation system. One company does the mowing. Another company or
the homeowner applies the fertilizer. Then, if necessary, another company applies the pesti-
cides. Better coordination and communication among ALL the people involved with mainte-
nance is required to insure healthy turfgrass.

Cultural Control Practices
Cultural practices should promote an environment that is not conducive for pathogen
infection and disease development. We realize you cannot change weather patterns (the overall
environment), but you can change localized environments. Water-saturated soils due to exces-
sive irrigation are a local environmental condition created by humans. The north side of the
house is cooler and receives less sun than the south side. A big oak or ficus tree creates a local
environment that is much different than under a palm tree or in an area with no trees. Remem-
ber that every maintenance practice, fertilizer application and chemical application has an im-
pact on turfgrass health.

If a disease should affect turfgrass, cultural practices should be implemented first or at
the same time that fungicides are applied. If a particular home lawn, recreational site, or com-
mercial landscape has a history of developing a particular disease at a particular time of year,
then it makes sense to implement cultural practices to prevent this yearly reoccurrence. Before
you say to yourself that "this is easy to say but difficult to put into practice" THINK! Habits are
hard to break. Why do you implement a certain maintenance practice? Because that is the way
you have always done it? Is that a good reason? If changing a practice will prevent problems
later, then maybe it is reasonable to change that practice.

If you are a landscape maintenance professional, explain to the landscape owner
your reasons for altering a practice. Provide them with records indicating disease outbreaks,
cost of fungicide applications, turf replacement, etc. Explain the potential benefits for altering a
maintenance practice in both economical and ecological terms.

The cultural practices discussed below are all designed to alter the turfgrass envi-
ronment to prevent diseases or at least lessen their severity. For more specific details on each
topic, see the relevant chapters in the Florida Lawn Handbook.

Turfgrass selection

The selection of turfgrass species (St. Augustinegrass, centipedegrass, bahiagrass, etc.)
and cultivars within that species (example: 'Floratam' vs. 'Raleigh' St. Augustinegrass) should
be based on your location, and how the turf will be used and maintained. Selections that are not
suited for a particular area will be continually stressed, more susceptible to diseases (and other

pests) and require increased maintenance costs in terms of labor and pesticides. For example, it
is difficult to grow St. Augustinegrass without supplemental irrigation. Centipedegrass should
be grown on soils with low pH (below 6). Check with your county extension office for local

Mowing practices

Mowing is the most common turf maintenance operation, and the most damaging when
done improperly. Mowers must be sharp so they cut rather than tear the turf leaves. Turfgrasses
that are cut below their optimum height will become stressed and more susceptible to diseases,
especially root rots. This is especially true during periods of low light intensity (cloudy days)
or in shaded areas. Be sure to mow as frequently as necessary so that no more than one third of
the leaf is being removed at any one time. The actual recommended turf height depends on the
turfgrass species being grown. It is especially important not to mow St. Augustinegrass too
short, as the growing point of this grass is aboveground.

When any disease occurs, raise the cutting height! A low height of cut reduces the leaf
tissue necessary for photosynthesis, the process by which the plant produces energy for growth.
An active disease eventually reduces the leaf canopy and photosynthesis is reduced even fur-
ther. Raising the height of cut increases the green plant tissue available for photosynthesis
resulting in more energy for turfgrass growth, and the subsequent recovery from the disease.

Mulching mowers do not increase diseases. However, if a turfgrass area has an active
leaf disease, this area should be mowed last to prevent the spread of the disease. Likewise, wash
the mower with water after mowing the diseased area to remove diseased leaf clippings. Put
the clippings collected from diseased areas or washed from the mower into a compost.

Water management

While irrigation is essential to prevent drought damage during the dry season, the amount
of water and the timing of its application can prevent or contribute to disease development.
Most fungal pathogens that cause leaf diseases require free water on the leaf or very high hu-
midity to initiate the infection process.

Dew (more importantly, the length of the dew period) is a critical factor for leaf disease
development. Dew is dependent on temperature and humidity. Extending the length of the
dew (free water) period by irrigating in the evening before dew forms or in the morning after the
dew evaporates extends the dew period. Therefore, irrigate when dew is already present, usu-
ally in the pre-dawn hours. A good time range is between 2 and 8 AM. In addition, this will
dilute or remove the guttation fluid (fluid being forced out of the leaf tips by internal plant
pressure) that can accumulate at the cut leaf tip and may provide a food source for some patho-

Irrigate only when drought stress (curled leaf blades) is observed, and then apply enough
water to saturate the root zone of the turfgrass. Make sure the irrigation system is applying the
water uniformly across the area. Irrigating everyday for a few minutes is not beneficial for the
turfgrass because it does not provide enough water to the root zone, but it is beneficial for the
turfgrass pathogens.

Nutrition management

Many diseases are also influenced by the nutritional status of the grass, especially nitro-
gen. A perfect balance is the goal. Both excessively high and low nitrogen fertility contributes to
turfgrass diseases. Excessive nitrogen applications encourage Brown Patch and Gray Leaf Spot
diseases, whereas very low nitrogen levels encourage Dollar Spot disease. Remember, it is easy
to add nitrogen but impossible to remove it. Therefore, apply the minimal amount of nitrogen
required for your particular turfgrass type.

Potassium (K) seems to be an important component in the prevention of diseases, per-
haps because it prevents plant stress. Again, a non-stressed plant is not as susceptible to dis-
eases. This has probably best been documented with 'Helminthosporium' diseases. To main-
tain healthy turfgrass, the amount of elemental potassium applied should either be the same or
greater than the amount of nitrogen applied. In an area prone to disease, it may be beneficial to
increase the potassium level applied. It is important to remember that potassium will leach just
as readily as nitrogen. The use of both slow-release nitrogen and potassium sources is highly
encouraged. If it is not possible to obtain slow-release potassium, then apply smaller amounts
of quick-release potassium, but more frequently. This would be especially useful during the
rainy season.

Even micronutrient deficiencies may play a role in disease development, as is the case
with take-all root rot. Also, you can use micronutrients, specifically iron sulfate and manganese
sulfate applied as a foliar spray, to keep the turfgrass green rather than applying nitrogen.

When turfgrass roots are damaged or not functioning properly from diseases, nematodes
or water-saturated soils, it would be beneficial to apply nutrients foliarly (liquid nutrient solu-
tion sprayed on the leaf tissue). Damaged roots will have a difficult time absorbing nutrients
from the soil. Frequent applications of small amounts of nutrients to the leaves will help to keep
the plant alive until new roots are produced.

Thatch management

Thatch is the tightly bound layer of living and dead stems and roots that develops be-
tween the zone of green vegetation and the soil surface. It is a natural component of turfgrass.
When an excessive thatch accumulation occurs, it means plant tissue is being produced more
quickly than it is being decomposed. Thatch is decomposed by bacteria, fungi, earthworms and
other organisms that naturally live in the soil.

Factors that prevent or slow down decomposition are excessively wet or dry conditions,
very high or low thatch pH, inadequate or excessive nitrogen levels and repeated use of chemi-
cal pesticides that may reduce the level of organisms responsible for decomposition. These
factors may also be conducive for disease development. Physical removal is the best way to
eliminate excessive thatch. To prevent excessive thatch from occurring again, review your main-
tenance practices. Are you applying too much nitrogen? Are you applying too much water
when you irrigate? Or not enough? Correct those practices that may be promoting excess thatch

Soil physical and chemical status

Compacted soils will prevent proper drainage resulting in areas that remain excessively
wet. Once they dry out completely, they are often difficult to rewet. Turfgrass in these areas
may have root systems that are deprived of oxygen resulting in a weak plant. This is also an
ideal situation for root rots to develop. High soil pH may affect nutrient uptake and weaken the
plant. High salt concentrations will impact turfgrass health resulting in a plant more susceptible
to diseases.

If you have areas in the lawn or landscape that appear to dry out first or are the first to
appear 'sick', use a metal rod to be sure that there is nothing buried at that location. It is not
uncommon to find building materials buried in the landscape. If you have an area that is water
logged for long periods, build that area up and make it level with the rest of the lawn.

Chemical Control Practices

What is a fungicide?

Fungicide is the name for a pesticide used to manage fungal diseases. Fungicides sup-
press or slow down fungal growth or prevent the fungus from reproducing. They do not elimi-
nate or kill the pathogens in the turfgrass area. Most fungicides are active against a limited
group of fungi. This is why it is important to know which pathogen you need to control.

Fungicides do not promote the growth of the turfgrass. The only way healthy turfgrass
will reappear is when new growth occurs. For example: A leaf spot will remain on the leaf, even
after a fungicide is applied. This diseased leaf area will remain until it is removed by mowing,
and new leaf tissue replaces it. Since many of the turfgrass diseases to be described later occur
when the grass is not growing actively, complete recovery may be very slow. You may think
you are seeing no response to the fungicide application when in fact the fungicide has been
effective against the fungal target. It is simply that the turfgrass has not grown enough to replace
the diseased tissue.

When to use a fungicide

Fungicides should be used only during those time periods that are conducive for disease
development. It is acceptable to use fungicides on a preventive basis (prior to disease develop-
ment) as long as you really understand what diseases/pathogens you are protecting the grass
from at any given time of the year. For example: Why apply a fungicide to protect against
Pythium Blight on St. Augustinegrass when this an extremely rare disease on warm-season
turfgrasses? Why apply a fungicide to prevent take-all root rot when you have never observed
this problem in the landscape that you manage?

Only use fungicides when absolutely necessary as overuse has the potential to increase
or shift the disease spectrum on turfgrasses or lead to development of fungicide-resistant strains
of pathogens. Just because one site has a disease does not mean that disease will occur on the
lawn next door as the management techniques or turfgrass cultivar may be different. Remember
that the primary factor for turfgrass disease development in Florida is the environment, not just
the overall environment, but the microenvironment created by placement of the buildings in
your landscape site or your management practices. In fact, each side of the house may have its
own microenvironment as influenced by trees, other buildings, lakes, etc.

When you do use a fungicide, read the label and follow the directions regarding rates, the
amount of water needed to apply the product effectively, irrigation requirements, as well as
safety instructions for mixing, applying and storing the product. Almost all pesticide 'failures'
are due to misapplication, including misidentification of the problem! Don't waste your money,
become a safety risk, or pollute the environment by using a product incorrectly.

Think about fungicide applications relative to other maintenance practices. Unless the
clippings are returned to the turfgrass, do not mow for at least 24 hours and preferably longer.
The fungicide is probably on the leaf. If you mow and collect the clippings, you have also
collected the fungicide. Unless the product is supposed to be irrigated into the soil, do not
irrigate for at least 24 hours after a fungicide application. Ideally, the turf area should be mowed
and irrigated prior to a fungicide application to allow a maximum time interval between fungi-
cide application and the next turfgrass maintenance operation.

Fungicide categories

Turfgrass fungicides can be divided into four broad categories based on the location of
their activity: 1) contact fungicides, 2) systemic fungicides, 3) local-penetrant fungicides, and 4)
mesostemic fungicides. They can also be divided into very small groups based on chemical

Contact fungicides

Contact fungicides are generally applied to the leaf and stem surfaces of turfgrasses.
They are considered protective or preventive fungicides. They inhibit the fungi on the plant
surface so the fungus will not be able to enter/infect the plant. These fungicides remain on the
plant surface and do not penetrate into the plant. They remain active only as long as the fungi-
cide remains on the plant surface in sufficient concentration to inhibit fungal growth, usually 7
to 14 days. Leaves that emerge after the fungicide has been applied will not be protected. Any
fungus already in the plant will not be affected. To obtain optimum protection, it is important
that contact fungicides evenly coat the entire leaf surface and are allowed to dry completely
before irrigating or mowing.

Contact fungicides are normally used to control foliar diseases and not root diseases.
The exceptions would be those used to control Pythium root rot (chloroneb and ethazol). Con-
tact fungicides have a broad spectrum of disease control activity and have been used exten-
sively in the turf industry for a number of years. However, recent changes in labeling have
occurred. Mancozeb can only be applied by a professional pesticide applicator. Chlorothalonil
can no longer be applied to the turfgrass in residential landscapes (single-family homes, condo-
miniums and apartment complexes). It can be applied to the turfgrass of commercial land-
scapes and to the ornamentals in a residential landscape.

Systemic fungicides

Systemic fungicides are chemicals that do penetrate plant surfaces and are then translo-
cated (moved) within the plant vascular system, either in the xylem or phloem tissue. Except for
fosetyl-Al (Aliette) which is translocated in xylem and phloem (primarily phloem) tissue, sys-
temic fungicides are xylem-limited.

In general, systemic fungicides have curative and protective activities with extended re-
sidual activity. Because systemic fungicides are absorbed by the plants, they 'work' inside the
plant to: a) control pathogenic fungi which have already entered the plant and initiated a dis-
ease (curative action), and b) inhibit fungi that enter the plant from initiating a disease (preven-
tive action). Their residual activity is also due to the fact that the plant absorbs them. Once a
systemic fungicide is inside the plant, it will not be removed by water or degraded by sunlight.
Newly emerged plant tissue may contain sufficient concentrations of the fungicide to protect
them from fungal infection. Therefore, systemic fungicides do not need to be applied as often as
contact fungicides; usually 21-30 day intervals are adequate.

Systemic fungicides usually have a very specific mode of action and do not have as broad
a spectrum of disease control as contact fungicides. However, they will control both foliar and
root pathogens. When attempting to control root diseases, systemic fungicides should be wa-
tered into the root zone for maximum effectiveness. As indicted above, the majority of systemic
fungicides are xylem-limited. If the fungicides are only applied to the leaf tissue, the com-
pounds may never reach their root target in the amount needed for control.

Local-penetrant fungicides

Local-penetrant fungicides are capable of penetrating the plant surface, but they only
move very short distances within the plant and do not enter the xylem or phloem tissue. The
majority of the fungicide applied remains on or near the plant surface. Included in this group of
fungicides are iprodione and vinclozolin. These fungicides are considered protective/preven-
tive type fungicides. The discussion on contact fungicides applies to this group of fungicides

Mesostemic fungicides

Mesostemic fungicides are a new group of fungicides that includes trifloxystrobin (Com-
pass). This fungicide is strongly attracted to the plant surface and is absorbed by the waxy plant
layers. It appears to continuously penetrate the leaf surface. However, it is not translocated in
the plant vascular system (xylem or phloem), and so is not truly systemic. The fungicide is able
to redistribute itself on the plant surface via localized vapor movement and surface moisture.
This fungicide works best as a preventive fungicide. Because the fungicide is not directly ex-
posed to weathering factors, reapplication intervals will be 14-21 days.

Chemical names and classes

Each fungicide has three different names. It will have only one chemical name (a long
technical name based on its chemistry), and only one common name (a simpler one-word name).
This fungicide can have multiple trade or brand names. Fungicides are also divided into chemi-
cal classes based on their chemical properties and activities. Table 1 lists fungicides based on
chemical class and provides the common names of turfgrass fungicides and a trade name ex-
ample. Table 2 lists the common fungicide names and their corresponding chemical name.

To prevent fungicide resistance from developing in a pathogen population, it is impor-
tant to know which fungicides belong to the same chemical class. Fungicides in the same chemi-
cal class will have the same mode of action. Fungicides should be periodically alternated or
used in mixtures with fungicides belonging to different chemical classes to prevent fungicide
resistance. For example, alternating between Bayleton (triadimefon) and Banner MAXX
(propiconazole) does not mean you have alternated between chemical classes because both fun-
gicides belong to the same chemical class, the demethylation inhibitors.

Read labels!

You would not or should not give a family member any medication without following
the instructions on the label. Turfgrass pesticides deserve the same amount of respect. In addi-
tion to rates and intervals for application, labels provide information concerning the use or non-
use of additives (such as surfactants) with the material, compatibility with other pesticides or
fertilizers, amount of water to use in the application process, irrigation needs, posting or re-
entry restrictions, and more. Keep up to date with the labels. Every time you obtain a new batch
of pesticide, read the label. You should especially pay attention to where the pesticide can be
legally used, the total amount of product that can be applied in a year, and the restricted entry
interval. Remember, labels are the law; they are considered legal documents!

Except for chemicals used to buffer the water pH, do NOT add any additive (example:
surfactants) to a fungicide unless the label specifically states this is acceptable. The majority of
fungicides already have a surfactant as part of the fungicide formulation. NEVER mix fertilizer
solutions with fungicides, especially fungicides that contain metals (examples: mancozeb, fosetyl-
Al, chlorothalonil with zinc) without determining compatibility. It has taken years of research to
produce the fungicides currently on the market. Please take advantage of that knowledge by
reading the label and asking questions of university and chemical company researchers.

Biological Control Practices

Microorganisms naturally present in the turfgrass ecosystem will help reduce disease
potential or disease damage, but only if they are allowed to flourish. They accomplish these
tasks by: a) competing with the pathogens for food sources, b) producing chemicals that inhibit
the growth of the pathogens, or c) physically excluding the pathogens from the plant by occupy-
ing the space first. Therefore, it is just as critical to keep the soil microbial population healthy as
it is the turfgrass. Reducing pesticide use is one way this may be accomplished. Although
many products (sugars, enzymes, carbohydrates, etc.) are being sold that claim to increase natu-
ral microbial populations, there is no documentation that this does occur in home lawns or
landscapes in Florida.

Microorganisms not naturally present in your turfgrass environment can be introduced
in an attempt to control diseases. This can be done by applying organic materials that have
natural microbial populations (composts) or have had microbial populations added to them
(natural organic fertilizers with microbial supplements). In both cases, the products must be
applied prior to disease development as they work preventively and not curatively. Again,
there is no documentation that these products consistently prevent diseases. Natural organic
fertilizers should be used for their nutrient value (nitrogen and potassium) and not for any
possible secondary effects.

There are many products composed of living organisms, primarily bacteria and fungi,
being sold that claim they will increase turfgrass health. However, for any material to be consid-
ered a biological fungicide or microbial biopesticide, the U.S. Environmental Protection Agency
(EPA) must register it. EPA registration indicates that the safety of the product to humans, non-
humans (fish for example) and the environment has been determined. Materials that have not
been approved by EPA should be used with caution. Many naturally occurring bacteria and

Useful References for Turfgrass Diseases

Compendium of Turfgrass Diseases, Second Edition by R. W. Smiley, P. H. Dernoeden,
B.B. Clarke, 1993. Cost is approximately $30. Available from: APS Press, 3340 Pilot Knob Road,
St. Paul, MN 55121-2097 Phone: 1-800-328-7560 (continental U.S.) or 612-454-7250 Fax:

The above item is also available in an expanded form for your computer. Turfgrass
Diseases: Diagnosis and Management CD-ROM by G. L. Schumann and J. D. MacDonald. Avail-
able from APS Press (see above).

Diseases of Turfgrasses by H. B. Couch, 1995. Available from: Krieger Publishing Co.,
P.O. Box 9542, Melbourne, FL 32902-9542 Phone: 407-724-9542

Management of Turfgrass Diseases by J. Vargas, 1994. Available from: Lewis Publishers,
2000 Corporate Blvd. NW, Boca Raton, FL 33431 Phone: 1-800-272-7737

Color Atlas of Turfgrass Diseases by T. Tani and J. B. Beard, 1997. Available from: Ann
Arbor Press, Inc. 121 South Main St., Chelsea, MI 48118 Phone: 313-475-8787

Table 1. Turfgrass fingicides listed by chemical class.

Chemical Class ILocation ofActivity Ca onm Nane Trade Nane Exanple

Acetanilde Systemic; xylem-limited Mefenoxam Subdue MAXX
Aromatic Hydrocarbon Contact Chloroneb Teraneb
Etridiazole (also Ethazole) Koban, Terrazole
Quintozne (also PCNB) Terraclor
Benanide Systemic; xylem-limited Flutolanil ProStar
Bezimidazole Systemic; xylem-limited Thiophanate methyl Fungo, Cleary 3336
Benzonitiile Contact Chlorothalonil1 Daconil, Manicure
Carbai ate Systemic; xylem-limited Propamocarb Banol
Demethylation Inhibitor Systemic; xylem-limited Myclobutanil Eagle
(DMI, Triazole, Sterol Inhibitor) Propiconazole Batn rMAXX
Triadimefn Bayletn
Dicarboximide Local-penetrat Iprodione Chipco 26019
Vinclozolin1 Curalan
Dilhiocarbamate Contact Mancozeb2 Dilhane T/O
Thirani Spotete
Ethyl Phosphonate Systemic; primarily phloem Fosetyl-Al Aliette
f-methyoxyacrylate Systemic xylem-limited Azosystrobin Heitage
Oxinoacetate Mesostenmc Trifloxystrobin Compass

1Chloro1halonil, hianm, and vinclozolin cannot be applied to residential lawns (single-famy homes, condominiums and apartment
complexes). They can be applied to tufgass in business and industrial landscapes.
2Mancozeb can be applied to residential lawns only by a professional pesticide applicator.

Table 2. Common name and chemical name ofturfgrass fungicides.

Common Name Chemical Name

Azoxystrobin methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}3-methoxyacrylate
Chloroneb 1,4-dichloro-2,5-dimethoxybenzene

Chlorothalonil tetrachloroisophthalonitrile
Etridiazole (Ethazol) 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole
Flutolanil N-[3-(1-methylethoxy)phenyl]-2-(trifluoromethyl) benzamide
Fosetyl-Al aluminum tris (O-ethyl phosphonate)
Iprodione 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo--imidazolidinecarboxamide
Mancozeb coordination product of zinc ion and manganese ethylenebisdithiocarbamate

Mefenoxam (R)-2-[2,6-dimethylphenyl)methoxyacetylamino]-propionic acid methyl ester
Myclobutanil a-butyl-a-(chlorophenyl)-lH-1,2,4-triazole-l-propanenitrile

Propamocarb propyl [3-(dimethylamino)propyl] carbamate monohydrochloride
Propiconazole 1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl}-H-1,2,4-triazole
Quintozene (PCNB) pentachloronitrobenzene (PCNB)
Thiram tetramethylthiuram disulfide
Thiophanate methyl dimethyl 4,4'-o-phenylenebis[3-thioallophanate]
Triadimefon 1-(4-chlorophenoxy)-3,3-dimethyl-l-(1H-1,2,4-triazol-l-yl)-2-butanone

Trifloxystrobin (EE)-methoxyimino-{2-[1-(3-trifluoromethyl -phenyl)-ethylideneaminooxymethyl]-phenyl-
acetic acid

Vinclozolin 3-(3,5-dichlorophenyl)-5-ethenyl-5-methyl-2,4-oxazolidinedione

figure 1. damage trom an excessive rate
herbicide- no disease

lgure z. -t. Augustinegrass mowea too
short, resulting in 'scalped' turfgrass- no

Figure 3. Dry 'patches' in St Augustinegrass- no

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