The beginning of the year, when nature reawakens, is the time
to again think about caring for your lawn. It should fulfill your
requirements and meet your expectations. In order for a lawn to
remain in an optimal state, that is, for the soil to be aerated
and the water and nutrient supply to be ensured, tasks other than
mere mowing must be implemented.
The Most Important Care Activities for Lawns
Lawn care is greatly dependent on the demands of the lawn. A
representative lawn needs much more intensive care than a flower
lawn.
There are numerous fungal infections that can affect lawns, but
there are only a few that can cause such severe damage that countermeasures
are required. The most important diseases/infections are as follows:
Dethatching is done to remove thatch, which also removes moss.
During dethatching, rotating blades cut through the sod in distances
of 2-3 cm up to a soil depth of 1-3 mm. Dethatching is best done
at the beginning of the strong growth period (April) shortly after
pruning (with pruning product cleared). After clearing the thatch,
regeneration fertilization and follow-up sowing should be done.
Aerating a lawn improves the supply of oxygen to the roots. There
are two methods:
a) Spiking
Between 200 and 400 holes per m2 with a diameter of 1.5-2.5 cm
up to a depth of 5-15 cm are made into the lawn. When the raised
material is sand-rich, it can be distributed onto the lawn via
towing. The forming cracks and lumps increase the effectiveness
of the measure, as does the incorporation of sand.
b) Slitting
Slitting may only be done for arid soils. The slitters should
tear open the soil in distances of 10 cm up to a depth of 8-10
cm in a width of 0.8-1 cm. Slitting should preferably be done
between September and March.
Sanding helps improve or retain the physical soil properties
on the surface (porosity for gases and water, indenting of the
sod, evening out of the surface, mixing of earthworm droppings
to a base-layer-like mixture). Sanding is best done in the spring,
for example after sowing. Typically, 2-3 liters of sand per m2
are used. Weather-resistant sands (silica sand) with a granularity
of 0/2 should be employed for this, and the sand should be largely
free of lime.
Lawns should not be watered daily, because frequent watering
spoils the grass roots, and their deep growth is inhibited. This
results in deeper-situated water no longer being available for
the roots. Lawn watering should commence upon wilting. Small areas
exhibit a gray coloring of the lawn, and the grass blades are
slightly rolled up. Lawn watering should be done at the greatest
possible time intervals. Around 15-25 l/m2 of water should be
used when watering a lawn in order to permeate deeper layers (deep
root penetration).
Mowing is one of the most important tasks in caring for a lawn.
How short to mow the lawn should be adapted to the respective
lawn type. The lawn should always be mowed when it has grown 1/3
to a maximum of 1/2. The lawn should be mowed weekly or up to
once every two weeks. Always ensure that the blades of the mower
are sharpened so that you achieve a clean cut surface.
The Nutrient Ratio of Fertilizer
As various studies have shown, a constant nutrient ratio underlies
nutrient deprivation by lawn grasses: nitrogen 1: phosphorous
0.3:
potassium 0.6: magnesium 0.1.
Distribution of nitrogen requirements of lawn grasses
The distribution of the nitrogen requirements for lawn grasses
is clearly subjected to seasonal fluctuations (see Fig.). During
the summer, growth is slowed down due to dry weather conditions
and higher temperatures. During this time, the nitrogen supply
should also be kept rather minimal. High nitrogen quantities during
this phase can weaken the lawn’s resistance to dryness and
disease. Short days and low temperatures starting in the fall
cause grasses to stop growing. Therefore, no nitrogen should be
administered in the fall. If growth is not possible due to external
conditions (temperature, light, or water), administering nitrogen
fertilizer does not make sense. Excessive nitrogen leads to increased
susceptibility to fungal diseases and a heightened risk of nitrate
washout.
Fertilization Periodt
The first fertilization of the year should be done between the
beginning and middle of March, depending on the weather. The last
fertilization of the year should take place at the end of October
at the latest.
Why do some lawns have more weeds than others? The following
factors promote weed growth:
Inappropriate fertilization
Inappropriate care measures
Bad soil structure
Incorrect lawn mixture
Environment
If a lawn has weeds, they should be combated early in the spring
as well. A selective herbicide can be used for this. When the
weed infestation is very high (>30%) and there are also many
types of undesired weed grasses, it is expedient to resow the
lawn. This will destroy all the weeds and undesired weed grasses.
Moss Control
A high degree of moss in the lawn indicates that the area has
certain problems. The following factors affect moss infestation:
Mowing that is too low to the ground
Soils that are ill-supplied with nutrients
Badly structured soil
Moisture retention, shade
Selection of incorrect grass mixture
If the lawn has a high degree of moss in it, the above-mentioned
problems should be resolved if possible; otherwise, the moss will
spread again after a short period of time. Moss control is possible
starting in the middle of March, depending on the weather. Moss
control should first be attempted using machinery, before resorting
to chemical agents. The lawn is dethatched and fertilized and
combined with resoling, where needed.
Millet Control
If millets have occurred in recent years, it is advisable to
treat the lawn with a preventive solution in order to prevent
the accumulation of millets. The solution cannot be administered
until the soil temperature at the surface is over 20° C, because
the millets do not germinate until these conditions have been
achieved (beginning the middle of April).
There is not much that can be done against the spread of fungus.
Fungal spores are spread through the air, rain, or soil, or through
direct contact with people, animals, or tools. Both the underground
aerial parts as well as blades can be affected. Each variety of
fungus needs specific growth conditions: one needs warm and humid
weather, the other loves cool and damp environments, and yet a
third variety thrives in the winter under the cover of snow.
Causes of the spread of fungal diseases are as follows:
Continuous high degree of stress on the lawn
High air humidity
Shady location
Standing air
pH value too high or too low
Thick lawn thatch
Continuous deep cutting (mowing too close to the ground)
Excessive supply of water and nitrogen
Too much grass or thick foliage cover during the winter
Preventive Measures for Combating Fungal Diseases
When selecting seeds, opt for varieties that are resistant
to diseases
Avoid a strongly shaded location
Ensure aeration
Do not mow grass too close to the ground (deep cutting)
Ensure sharp lawn mower blades for smooth cutting
Balanced nutrient and water supply
Combating Fungal Diseases
If a lawn has been infected with a fungal disease, you should
first attempt to improve the habitat conditions. If the soil is
compacted or there is a thick layer of thatch, try to achieve
improved porosity and aeration through dethatching and aeration
measures.
This means the implementation of mechanical measures that correct
the compaction in the root area of the lawn up to a depth of 10
cm (spiking or slitting). It is advisable to subsequently administer
sand into the holes or crevices.
Annual Incidence of Fungal Diseases
The following table shows the times of the year that the various
fungal diseases can occur.
Snow mold fungus is a common disease in fine lawns, thus above
all in decorative lawns. The affected types are the following:
Agrostis spec. (bentgrass), Lolium perenne (perennial ryegrass),
and Poa spec. (bluegrass). Less affected are: Festuca rubra (red
fescue) and Timothy grass.
Snow mold fungus: Typical infection, a dark ring with mycelia.
As the name implies, this infection is promoted by long periods
of snow cover.
Symptoms:
In the spring, small, rough round spots with a diameter of around
2.5 to 5 cm appear; these spots grow up to 30 cm in circumference
under unfavorable conditions and can overlap. A dark brown ring
can form at the edges of the circles, which signifies the active
zone of the infection. The spots are covered by a film of grayish
white to red mycelia.
Combating the Fungus:
· Improvement of the soil porosity through dethatching
or aeration
· Improvement of the soil porosity through dethatching
or aeration
· Balanced fertilization; use of potassium-rich fertilizer
in the fall
This disease primarily occurs in the spring or late summer and
fall. It typically appears in moist and ill-aerated soil.
Agrostis spec. (bentgrass) and Festuca rubra ssp. Rubra (red fescue)
are especially susceptible
Dollar spot: Straw-yellow colored, sharply defined spots
Symptoms:
Initially, individual yellow-colored spots around 1 to 2 cm in
diameter appear, some of which grow to a diameter of 5 to 15 cm.
They distinguish themselves sharply from the healthy grass. In
conditions of high air humidity, fine whitish mycelia can be seen.
In the case of severe infection, the root growth can also be affected.
Combating the Fungus:
Eliminate any thatch layers and soil compaction through aeration
and dethatching.
Ensure appropriate nutrient supply. Excessive administration of
nitrogen and potassium increase susceptibility.
This disease afflicts primarily all fine-bladed grasses, such
as Agrostis tenuis (colonial bentgrass), Agrostis canina (velvet
bentgrass), Poa spec. (bluegrass), and Festuca spec. (fescue).
Heavily limed and nutrient-poor, ill-drained lawn locations are
affected in the late summer, fall, and winter.
Black Root Rot: Large ring with typical bronze discoloration
Symptoms:
Small, caved-in spots measuring around 5 to 10 cm in diameter
appear initially, which can then grow to 1 m in diameter. The
caved-in areas first appear dark green and later turn light brown
or reddish. In the center of the spots, the grasses die off and
weeds develop. The grass can be easily pulled out of the ground,
and the roots are brown-black in color.
Combating the Fungus:
Improvement of porosity
With appropriate pH value, no liming and no administration
of lime-containing fertilizers
Powdery mildew occurs primarily on lawns in shaded locations.
Powdery mildew thrives when the lawn is left too high when mowing
and under warm humid conditions.
Symptoms:
A white to gray-white film develops on the surface of the blade,
especially in young blades; this film eventually turns into a
flour-like cover.
Combating the Fungus:
More light
Loosening of the compacted, wet soil
Keep mowing height at 2.5-3 cm
Fertilizing with potassium and phosphate decreases risk of
infection; fertilizing with nitrogen, calcium, and magnesium
increases the risk
Red thread primarily occurs in decorative lawns, but also in
other types of lawns, when the nutrient supply is insufficient.
Especially susceptible to attack is the Festuca rubra (red fescue),
but Agrostis spec. (bentgrass), Poa pratensis (Kentucky bluegrass),
and Lolium (ryegrass) can also be afflicted. Fungal infections
occur mostly after warm humid periods from June to October. Red
thread disappears in dry weather conditions.
Red thread: The close-up shows the red, geweihartig stoma
Symptoms:
The first signs are irregularly formed spots which, over the course
of the infection, turn light brown and then hay-colored. You often
find healthy grass inside the diseased areas. In conditions of
high air humidity, cotton-like, rose-colored mycelia occurs.
Combating the Fungus:
Improved nutrient supply with phosphorous, potassium, and
especially nitrogen (use long-term fertilizers)
Poa pratensis (Kentucky bluegrass) and Lolium perenne (perennial
ryegrass) are especially susceptible to lawn rust. Lawn rust occurs
primarily from May to September after periods of dry weather.
Pustule formation during infection
Symptoms:
Light green spots begin to appear on the blades when the infection
hits. Then yellow, orange, or brown pustules develop very quickly
with dust spores in various forms and arrangements. The afflicted
grasses fall behind in their growth.
Combating the Fungus:
Balanced fertilization and water supply
Regular mowing, so that the grass does not become too high,
but do not mow too close to the ground
Prevent planting host plants for the rust fungus, such as
barberry or buckthorn, in the direct vicinity
This disease especially affects Poa pratensis (Kentucky bluegrass),
but other bluegrasses are also susceptible. The damage can occur
year round to a small degree.
Leaf spots: Brown-colored spots with a dull white center
Symptoms:
Sharply edged oval, dark brown to red spots appear on the blades.
The center of the spots dies off and becomes hay-colored.
Just like snow mold fungus, root rot is a typical winter disease.
Grass is afflicted in the late fall or winter, and the disease
becomes visible in the early spring, after the snow melts. Primarily
afflicted are Agrostis spec. (bentgrass), Poa spec. (bluegrass)
and Lolium perenne (perennial ryegrass).
Root rot: Whitish gray mycelia
Symptoms:
Light grayish fungal mycelia covers the plants in spots measuring
between 5 and 40 cm in diameter. At first glance, this disease
can easily be mistaken for snow mold fungus. However, with snow
mold fungus, the afflicted plants are moist and slimy to the touch,
whereas with root rot, they are dry and paper-like.
Combating the Fungus:
In the winter, the lawn should be about 3 to 3.5 cm high
Fairy rings can occur anywhere where grass grows. They are not
linked to specific grass types and can occur all year round. In
addition, sparse, sandy locations and former woodlands are also
prone to this affliction.
Type I fairy rings: Clear zones of dead grass
Symptoms:
There are three types of fairy rings, each of which is caused
by a different fungus.
Type 1:
This type causes the greatest amount of damage to lawns. In this
type, the grass between two parallel dark green rings dies off
completely.
Type 2:
This type is distinguished by a dark green ring with increased
grass growth in which many fungal fruiting bodies grow over the
course of several years. No visible damage can be seen on the
lawn.
Typ 3:
This type of fairy rings is characterized by circular fruiting
bodies (mushrooms). The lawn is not damaged.
Combating the Fungus:
·Balanced nutrient supply
Good aeration of the soil through dethatching, aeration,
and sanding
To combat the deep-reaching fungal mycelia, this layer must
be “poked through” as deeply as possible (bar spade,
“deep” soil loosener) and subsequently be thoroughly
watered
