PROBLEMS ON
CENTIPEDEGRASS
Centipede decline is a name used to describe the most common problem observed on
centipedegrass. Recent research in North Carolina has shown that this problem can be
caused by several different factors.
Nutritional factors, including low potassium levels in sandy soils, high phosphorus
levels, the use of too much nitrogen fertilizer, and low or high soil pH (5.5 is best)
have been associated with the problem. High soil pH will cause centipedegrass to turn
bright yellow, especially in the spring, due to iron deficiency (iron chlorosis). High
phosphorus levels can increase iron chlorosis since it can replace iron in the plant. The
use of fertilizers high in phosphorus may contribute to the decline of centipedegrass.
Soil test results should be used to correct these problems and to determine fertilizer
requirements.
Nematodes have been associated with the decline in sandy soils in some cases. The sting
nematode has been shown to cause very serious damage on centipedegrass in sandy soils in
southeastern North Carolina. Centipedegrass affected by this nematode will become
thin and even die during hot-dry weather. The importance of the ring nematode which occurs
frequently in centipedegrass lawns is not known. Damage from large numbers of this
nematode has not been observed in many test plots
established in the state. Since no nematicides are currently labelled for use in
residential lawns, management practices will have to be used to help overcome damage from
nematodes. A good management program that includes irrigation when needed can be used to
overcome the effect of the
ring nematode, but not the sting nematode. Another grass such as bermudagrass or
bahiagrass may be an alternative to use in centipede lawns with high levels of sting
nematodes. Incorporation of organic matter in the soil may help overcome nematode damage;
however, care must be taken to
avoid too much nitrogen being released for centipedegrass.
Fairy rings have been shown to be the cause of some centipede decline problems. Fairy ring
symptoms are large circular dead spots, dead rings, or green rings (3 to 20 feet in
diameter) that enlarge for several years. Mushrooms of the fungi that cause this disease
may be present at the edge of the rings or throughout the circles sometime during the
year. Mushrooms may not develop for several years and suddenly appear following
weather pattern that induces mushroom development. Effective treatments
are not known for fairy rings in lawns, however, rototilling the soil and replanting
healthy grass has eliminate the problem in some cases.
Ground pearls which are small scale insects that attack the roots of centipedegrass may
cause circular dead areas that resemble fairy ring. The spots enlarge each year and
only weeds grow in the spots. Ground pearls are identified by the presence of small
pearl-like bodies on the roots or in the soil. The pink adult stage that crawls is present
during early summer. A control is not know for the ground pearls. Other types of grass,
such as bermudagrass or bahiagrass, appear to be less sensitive to ground pearls and
should be considered for lawns with severe ground pearl problems.
Improper mowing and fertilization have been
indicated as factors in experimental plots where centipede decline developed. More decline
was observed in the spring where the grass was mowed at 2 inches than at 1 inch and where
high nitrogen rates (2 pounds per 1,000 sq. ft.) were used. More thatch accumulated
at the higher mowing height with high nitrogen and caused the stolons to be above the
soil. These stolons are more susceptible to damage by cold weather. More centipede decline
usually occurs in the spring and summer following very cold winters or following winters
with unusually warm weather and then late cold periods. Excess nitrogen increases the
thatch and reduces cold and drought tolerance of centipedegrass. Usually not more than 1
pound of nitrogen per 1000 sq. ft. per year is needed on sandy soils. The use of
fertilizers that are high in potassium and low in nitrogen may help to reduce stress
during the summer and winter. This grass has grown well on clay soils without any
fertilization for many years. Centipedegrass has a naturally light green color when
managed properly. If a darker green turf is desired in the lawn, another type of grass
such as bermudagrass or zoysiagrass should be considered.
Centipedegrass is not very drought tolerant and may be damaged during very dry weather.
Irrigation when needed will help reduce damage from drought stress. Localized dry spots of
soil that are hydrophobic (difficult to wet) have been associated with declining patches
of centipedegrass. The soil in these patches may be powder-dry even after rain or
irrigation. Loosening of the soil and heavy irrigation is needed to wet the soil in
these spots.
The use of certain herbicides (as sprays or in fertilizers) has been associated with the
decline problem. Centipedegrass is very sensitive to some herbicides and recommended
herbicides should be used according to label directions for centipedegrass. Damage has
been observed where fertilizers containing some types of herbicides have been applied at
rates suggested for other types of turfgrasses. In addition to herbicide damage, too much
nitrogen is often applied from the herbicide plus fertilizer products for centipedegrass
and causes problems discussed above. Once a good stand of centipedegrass is established,
weeds usually are not a problem because of the allelopathic activities that centipedegrass
has against other plants. Therefore, herbicides should not be needed each year on
centipedegrass if it is managed properly.
Centipedegrass is not very shade-tolerant and does not grow well under trees with dense
foliage. Root competition from nearby trees may increase drought stress and sometimes
causes fairy ring-like symptoms. The landscape should be redesigned to use mulch or
shade-tolerant plants in these areas if the trees cannot be removed.
Dollar spot is a disease that is often seen on centipedegrass during the summer. The
symptoms of this disease are light brown spots 2 to 4 inches in diameter. It does not
appear to cause serious damage.
Centipedegrass that is declining because of other
factors may have more dollar spot than nearby healthy grass. Brown patch has been
identified on centipedegrass during wet weather in the spring, summer and fall. The
symptoms in cool, wet weather are usually large circular patches of thin grass, however,
early symptoms may be circular yellow patches. The grass may continue to decline in the
affected patches, especially in dry weather, for a long time after the disease has stopped
activity. Some fungicides may help control these diseases, but usually are not needed.
Centipede decline may be caused by a number of different factors and accurate records of
previous treatment may be useful in diagnosing the problem. Centipedegrass will usually
spread over dead areas more rapidly if the old grass is removed and the soil loosened. New
sprigs should be planted in the areas in late spring or early summer for faster recovery.
Additional information on the management of centipedegrass and diseases is given in the
N.C. Agricultural Extension Publications AG-381, "Centipedegrass Lawn Maintenance
Calendar", and AG-360, "Diseases of Warm - Season Grasses." Your local
Cooperative Extension Agent can provide these publications and additional information.
NEMATODE DAMAGE AND MANAGEMENT IN LAWNS
Nematode damage can be severe in some lawns in southeastern and southcentral North
Carolina where soils are very sandy. Turf affected by nematodes usually appears weak and
thin. It may have symptoms of nutrient deficiencies or wilts rapidly during dry weather.
Similar symptoms may be caused by other problems such as poor fertility, lack of moisture
and some diseases. Root stunting, excessive branching and even death of roots may occur
with some nematodes. These symptoms are not usually adequate to identify nematodes as the
major problem, therefore, soil samples must be assayed for nematodes. Also, a soil
fertility test is recommended to eliminate nutritional problems as a major factor.
Nematodes are small eel-like worms that are too small to be seen without a microscope.
Nematodes that attack plants have small needle-like stylets which are used to puncture
plant cells to obtain nutrients. Different nematode species that attack turfgrasses cause
root stunting, death of roots, knots on roots and some cause no apparent harm even at high
numbers. Nematodes usually do not kill the host plants, but they do increase damage from
other stresses, such as drought. Ground pearls (soil insects) cause serious damage in
sandy soils on centipedegrass that can resemble nematode injury. If this insect is
present, some of the suggestions for reducing nematode damage may be useful.
Nematodes that are found most frequently in soil from turfgrasses are ring, stunt, spiral,
lance, stubby-root and sting. Only the sting and the stubby-root nematodes have been shown
to cause severe damage on turfgrasses in research projects at North Carolina State
University. The sting nematode is known to be the most damaging nematode and frequently
occurs in the sandy soils of eastern and southcentral North Carolina. It is difficult to
grow good quality turfgrasses where this nematode is present.
Nematicides are not currently labelled for the control of nematodes on turfgrasses in home
lawns. Good turf management practices must be used in place of nematicides in home lawns
to grow healthy turfgrasses that can tolerate some nematode damage. Some organic soil
amendments, such as shrimp and crab shells, may encourage fungi that kill nematodes.
Incorporation of organic matter in the soil before planting will help the soil
increase antagonistic microorganisms and help grow healthier turfgrasses. High rates of
organic matter should be used carefully on centipedegrass because too much nitrogen may be
released and cause excessive growth that would result in decreased drought and cold
tolerance.
Some management practices can be used to help minimize the damage from nematodes. The use
of good fertilization programs to insure proper levels of nutrients, irrigation to supply
adequate soil moisture, and recommended cutting heights will help turfgrasses tolerate
certain levels of damaging nematodes. In some cases an alternative turfgrass may be
considered. For example, centipedegrass is more susceptible to the sting nematode than
bermudagrass or bahiagrass . Therefore, bermudagrass would be the best choice for use in
residential lawns where high quality turf is desired if irrigation is available.
Zoysiagrass has been observed to be very sensitive to damage from sting nematodes and
would not be a good replacement for centipedegrass in sting nematode infested soil.
Bahiagrass may be the best choice for lower quality lawns and in large commercial lawns in
eastern North Carolina. Very little damage from nematodes has been observed on this course
textured grass.
Nematode management practices must be incorporated into lawn management systems where
nematode damage occurs. This approach will offer new challenges to turf managers and
homeowners since chemicals are no longer available to control nematodes in residential
lawns.
DISEASES OF BENTGRASS ON HIGH-SAND-CONTENT GOLF GREENS
Bentgrass has been difficult to manage on some golf greens constructed in recent years.
Most of these greens have been constructed using 80 to 90% sand, mixed with some type of
peat. The advantages of these mixtures are high percolation rates that allow play to
resume soon after heavy rains and the reduction of compaction problems. The disadvantages
are the decline of bentgrass on these greens from diseases, nutrient deficiencies and
imbalances and harmful soil and water relationships.
Deep root systems usually develop in the sand mixtures during the fall and spring but
decline severely during the summer. The first above ground symptom associated with the
root decline is yellowing of the grass. The turf continues to decline and becomes weak and
thin and may die in late summer. This condition is often referred to as black layer or
Pythium root rot, however, the name summer decline seems more appropriate since a number
of factors have been associated with the problem.
A black layer may develop near the surface, or deeper in the soil, and has been indicated
as the cause of the decline in some states. The black layer appears to be a symptom of the
problem because anaerobic (lack of oxygen) conditions in the soil are needed for it to
develop. The black layer is visible in the high- sand-content greens due to the light
color of the sand. It is formed from the reduction of sulfur compounds in low oxygen
conditions to sulfides that combine with iron and manganese which are black. Sulfur is
oxidized to sulfates which are not black in soils with good aeration. The first indication
that this layer is developing is a bad smell, like rotten eggs, from sulfides in the soil.
The lack of oxygen (drowning) can kill the bentgrass roots and the sulfides can be toxic
to roots. Therefore, the roots probably die sometime before the black layer becomes
visible in the soil. Also, algae have been indicated as the cause of the black layer, and
are associated with the problem in many cases. The growth of algae is favored by wet soils
which produce substances that interfere with the movement of water in sandy mixtures.
The algae contribute to the development of anaerobic conditions. The best
management practices to avoid anaerobic conditions, black layer and algae problems are to
irrigate carefully and to aerify the greens as often as needed. The mancozeb fungicides
can be used to help control some diseases and algae in combination with the management
practices.
The development of a thatch layer on the surface of high-sand-content greens contributes
to the decline. The thatch layer which has a finer texture than the sand below causes a
perched water table and water does not move into the sandy mixture until the layer becomes
saturated. Water can be squeezed out of the thatch layer in a plug from these greens for
several days after irrigation although the sand mixture below is relatively dry. This
saturated condition in the thatch layer causes an anaerobic condition, favors the growth
of algae and provides an environment favorable for fungi that cause brown patch and
Pythium root rot. A layer of thatch is necessary on these greens to obtain acceptable ball
holding qualities. However, mixing of a proper topdressing soil with the thatch is needed
to reduce the adverse effects of the thatch layer. Applications of topdressing soil
in combination with aerification in the spring and fall has worked best. Aerification with
small hollow tines or solid tines has helped to reduce the problem of saturated thatch
layers during the summer. Reseeding with bentgrass following aerification in the summer
has aided in recovery in some cases. Topdressing with large amounts of sand should be
avoided in the summer since abrasive damage from traffic and equipment can cause more
damage when the bentgrass is weak. Localized dry spots are often a severe problem on
high-sand-content golf greens. Dry spots of soil are thought to be caused by sand
particles becoming coated with microbical products. Once the soil in these spots becomes
dry, it is almost impossible to wet again without aerification or using wetting agents.
Stress from dry wilt and extra water needed to wet these areas make bentgrass more
susceptible to diseases such as Pythium root rot. Most superintendents have found that it
is best to use wetting agents in a preventative program and to keep sand mixtures moist to
avoid severe problems associated with localized dry spots. A dry ring is often a problem
at the edge of high-sand-content greens where the greens mixture meets native soil. The
native soil draws water away from the sand resulting in a dry area. The sand mixture
should extend out far enough off the green to have the fairway grass growing on the sand
mixture or use a barrier between the sand mixture and the native soil to solve this
problem.
Nutrient deficiencies and excessive nutrient levels have been identified frequently as
problems on high-sand-content greens. Sand mixtures often have very low cation exchange
capacities, often less than 2, that cause rapid leaching of nutrients. The low cation
exchange capacities and rapid leaching require application of more fertilizer on these
greens. Some greens have needed as much as 20 pounds of nitrogen per 1000 square feet
during the first year. Small amounts of a complete fertilizer with micronutrients should
be applied at frequent intervals to keep nutrients in the root zone.
High soluble salts from too much fertilizer have caused damage on many of these greens due
to the low cation exchange capacities and accumulation of salts in the thatch layer. As
water evaporates from the turf and soil, the salts may be concentrated around the crowns
of the plants. The symptoms of high soluble salt damage are large areas or streaks on a
green that turn yellow, begin to decline and even die a few days to several weeks after
fertilization. The problem is usually more severe during dry weather when small amounts of
irrigation water are being applied. The streaks are usually where the fertilizer
application overlapped. Once high soluble salts are detected, which involves a simple
extraction procedure and the measurement of electrical conductivity, leaching with large
amounts of water from irrigation or rain is the only way to remove them. Smaller amounts
of fertilizer should be applied each time to these greens than to ones with higher cation
exchange capacities. Even smaller amounts of slow release fertilizers should be used.
Soil test and tissue analysis should be used regularly to determine fertilizer needs of
the bentgrass. Soil test results for high-sand-content greens usually indicate a
deficiency of phosphorus, potassium and some micronutrients The accuracy of
recommendations for large quantities of nutrients for low- cation-exchange-capacity
mixtures is questionable because tissue analysis from clippings from these greens often
show adequate levels of nutrients. Soil test results should be used as a guide to correct
any pH problems, nutrient deficiencies or nutrient imbalances by applying small amounts of
nutrients at frequent intervals. Application of large amounts of potassium, which is
often indicated, at one time could result in damage from high soluble salts. The use of a
complete water soluble fertilizer dissolved in the spray tank and sprayed at low rates,
often 1/8 pound of nitrogen per 1000 square feet, has worked well on high-sand-content
greens. This fertilizer application method is very useful during the summer and has been
used all year in some cases.
Environmental conditions surrounding bentgrass greens are important for all types of
construction, but are very important for the high-sand-content greens. Summer decline
usually appears first on greens in low areas that are surrounded by trees on the east,
south and west sides. Wind movement is usually restricted in these areas and results in
hotter and more humid environments than on nearby open greens. Trees and undergrowth
should be removed on the southwest side to improve air movement from predominant southwest
winds during the summer. The surface temperature of greens with restricted air flow is
usually higher than nearby open greens.
Diseases caused by fungi are often a problem on all types of bentgrass greens. Bentgrass
on sand mixtures often appears more succulent and more susceptible to brown patch and
Pythium blight. A fertilization program with the lowest levels of nitrogen possible in the
summer will help reduce the susceptibility to these diseases. Pythium root and crown rot
is very prevalent on high-sand- content greens. Pythium species that cause rot and crown
rot have been isolated from as many as 90% of the plants sampled from these greens. These
fungi apparently do not cause significant damage unless plants are weakened by some
condition such as anaerobic soil conditions, localized dry spots, high soluble salts or
environmental stresses. Correcting or avoiding these conditions will help to prevent
damage from this disease in the summer decline complex. A preventive fungicide program is
needed during hot and humid weather to help control brown patch and Pythium blight.
Pythium species that cause root and crown rot are different than the species that cause
Pythium blight. These fungi, many of which are Pythium graminicola, are not sensitive to
Subdue and Banol but are sensitive to Koban and Fore. Using Koban at 5 to 6 ounces per
l000 square feet in 5 gallons of water as a preventative treatment has help controlled
Pythium root and crown rot in some cases. This treatment does not work well once the
bentgrass has started to decline. A combination of good management, summer aerification
and use of Koban has given the best results.
Some nematodes have been found in sand mixtures. The most damaging nematode found
frequently is the stubby root nematode. This nematode prefers a course wet sand like used
in these greens. It has been difficult to manage this nematode because the currently
available nematicide for golf greens, Nemacur, does not control the stubby root nematode
very well. A good healthy turf is the best means of overcoming damage from this nematode.
Good quality bentgrass can be grown on many high-sand-content golf greens if proper
construction and management techniques are used. Great care should be taken during the
construction process to ensure that proper sand and peat types are used and mixed
uniformly. Mixing can be done best off site prior to moving the mixture to a green with
very carefully prepared subsurface contours. The mixture must have a uniform depth, 12 to
14 inches, over the green for proper results.
Use of sands that have correct particle sizes and mix properly with the organic matter to
give desired percolation rates in the 10 to 15 inch per hour range is the first step in
preventing many of the problems associated with these greens. This can be done only by
using physical soil analysis which is available from several different laboratories.
Samples should be taken from the sand at time of delivery and analyzed to be sure that all
of the sand meets specifications.Special attention should be given to the selection of
topdressing mixtures to avoid layers of different types of soils. The same mixture used in
greens construction would be best if the greens are performing well. Mixtures different
from the original mixture should be used only following aerification so that it will mix
with the top 3 to 4 inches of existing material. The type of peat or organic matter used
in the mixture will make a big difference in soil properties. For example, a sand
mixed with a sphagnum peat resulted with a mixture that had a percolation rate of 17
inches per hour. The same sand mixed with a reed-sedge peat resulted in a mixture with a
percolation rate of 5 inches per hour. The addition of some loamy soil, especially with
sphagnum peat, to increase cation exchange capacity has worked well in some cases.
Addition of some sandy loam soil resulted in greens that were easier to manage,
however,follow physical analysis recomend- ations for any materials used.
The USGA recommendations for golf green construction are the best guidelines to follow for
drainage, subsurface contouring and the addition of the top 12 to 14 inches of sand
mixture. Also, you should recognize that high-sand- content greens may need a totally
different management program than that used on old greens or on greens with different
mixtures. These high-sand-content greens usually become easier to manage after several
years of growth.
The use of brand names and any mention or listing of commercial products or services does
not imply endorsement by the North Carolina Agricultural Extension Service nor
discrimination against similar products or services not mentioned. Individuals who use
agricultural chemicals are responsible for ensuring that the intended use complies with
current regulations and conforms to the product label.
DISEASE-LIKE PROBLEMS ON TURFGRASSES
IN NORTH CAROLINA
Slime molds appear as gray to black growths in small circular patches on leaves of
turfgrasses. These growths are fungi that are slimy in wet weather that develop into a
powdery mass of spores a few days later. Slime molds cause very little damage to
turfgrasses. Some damage may occur if the fungal growth is heavy enough to cause shading
of the affected leaves. The fungi can be removed by brushing, washing, or mowing the
affected leaves. Broad spectrum fungicides can be used to control slime molds if large
areas are affected and the turf becomes unsightly.
Moss may be a problem in lawns with too much shade, low soil pH and low nutrient levels.
Mosses are short, light green to brownish plants that grow in shady areas. Removal of
excess shade and application of fertilizer and lime as recommended from a soil test will
help turfgrasses grow in areas with mosses. Moss may be an alternative to grasses if the
area has very little traffic and if a low maintenance landscape is desired.
Algae are single-celled plants that grow on the surface of wet soils or in water. Algae
may appear as a black slimy growth on the surface of a poorly drained soil in wet weather
and may form a crust which cracks and curls when the soil becomes dry. It is usually a
problem in areas that do not drain properly, have too much shade and a low soil pH. Algae
can be controlled by improving soil drainage and eliminating shade and soil nutrient
problems.
Animal urine can damage turfgrasses because of high soluble salts and nitrogen levels.
Grasses may be killed in small circular spots 1/2 to 1 foot in diameter. The surrounding
grass becomes greener and cool-season grasses become clumpy or weeds invade the dead
areas. Warm-season turfgrasses that spread by stolons and rhizomes may be killed in spots,
however, these grasses will usually spread into the affected areas quickly. Dark green
spots with taller grasses usually remain for several weeks. The damage to turfgrasses is
caused by the high soluble salts from the urine and the greening is caused by
nitrogen-containing compounds in the urine. The effects can be reduced by irrigating to
leach the salts deeper into the soil. Grasses such as tall fescue should be replanted in
the spots before weeds become established.
Shade and tree root competition is a common problem in lawns. Often,lawns with trees that
had enough sunlight to grow good quality turfgrasses a few years ago become too shady
because the trees have enlarged. Most turfgrasses will not grow well in areas that receive
less than 50% sunlight. This amount of sunlight may filter through pine trees but not
through the canopy of hardwood trees such as oaks and maples. To allow enough sunlight for
growth of turfgrasses, lower limbs or whole trees may need to be removed. Ground covers
that grow in shady areas, or some type of mulch, may be used in areas with too much shade
for turfgrasses. Root competition will cause areas near trees to wilt during dry weather
and have poor color. Additional fertilization and irrigation may be needed on turfgrasses
near trees.
Soil compaction from construction or traffic (walking, vehicles, playing or animals) may
result in poor growth of turfgrasses. Proper oxygen and water relations in the soil are
disrupted by compaction. The soil should be loosened by renovating or coring to relieve
the compaction for better growth of turfgrasses. High soluble salts from too much
fertilizer or the use of irrigation water high in salts can damage turfgrasses. Too much
salt in the soil does not allow the roots to take up sufficient amounts of water or will
draw water from the roots. Damage from very high rates of fertilizer can be seen in a few
days. Evaporation and use of water in the soil by the turfgrass plants during dry weather
can concentrate soluble salts to the point that damage may occur. Proper amounts of
fertilizer should be distributed evenly over the lawn. Care should be taken to avoid
spills or overlapping of fertilizer. Soluble salt damage from too much fertilizer may be
in streaks or spots from uneven application, whereas damage from salts in animal
urine will be in small circular spots. Irrigation to keep the soil moisture at proper
levels can prevent soluble salts from reaching damaging levels during dry weather. If high
levels of soluble salts are detected in the soil, extra irrigation or long periods of
rain, are needed to leach the salts deeper into the soil. The warm-season grasses usually
will recover from short exposures to high soluble salts, but the cool-season grasses may
be killed.
These problems often resemble diseases and the cause must be correctly identified so that
proper corrective measures can be selected and used.
RECOMMENDATIONS OF SPECIFIC CHEMICALS ARE BASED UPON INFORMATION ON THE
MANUFACTURER'S LABEL AND PERFORMANCE IN A LIMITED NUMBER OF TRIALS. BECAUSE
ENVIRONMENTAL CONDITIONS AND METHODS OF APPLICATION BY GROWERS MAY VARY WIDELY,
PERFORMANCE OF THE CHEMICAL WILL NOT ALWAYS CONFORM TO THE SAFETY AND PEST CONTROL
STANDARDS INDICATED BY EXPERIMENTAL DATA. ALL RECOMMENDATIONS FOR PESTICIDE USE WERE LEGAL
AT THE TIME OF PUBLICATION, BUT THE STATUS OF REGISTRATION AND USE PATTERNS ARE SUBJECT TO
CHANGE BY ACTIONS OF STATE AND FEDERAL REGULATORY AGENCIES.
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.
Employment and program opportunities are offered to all people regardless of
race, color, national origin, sex, age, or disability. North Carolina State
University at Raleigh, North Carolina A&T State University, U.S. Department of
Agriculture, and local governments cooperating.
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