| More on Lawn Diseases |
Foliar and
root diseases can affect both warm- and cool-season grasses. The disease-causing
fungi are almost always present in the soil waiting for a time when conditions
are right (or wrong) to attack. The most common times are when the host
(turfgrass) is under stress. Examples of environmental stress are excessively
wet or dry weather and exceptionally hot or unseasonably cool temperatures.
In addition
to being a reaction to environmental changes, lawn diseases can also be
signals of soil problems. Any part of a lawn can be affected. Slopes,
depressions, high traffic and shady areas are vulnerable. Improper mowing
or watering habits, too much or too little fertilizer, thatch and compacted
soil all increase the chances of disease.
Diseases
often start as yellow, tan or brown areas of varying sizes in the lawn.
But before you assume you have a lawn disease, make sure it isn't something
else. Injury, stress or deficiencies can produce similar symptoms and
also set the stage for infection. These are often things that you can
control, so it's wise to recognize and remedy these situations.
To help
identify whether the problem is injury, stress or a deficiency, here
are some examples:
Injury
Pesticide, fertilizer
or gasoline spills |
Refill spreaders, sprayers and outdoor power equipment carefully.
Use a funnel or a "no-spill" container. Dry products can
be raked up, collected and used. Flood the area with water to dilute.
Liquid spills need to be removed with an absorbent product and disposed
of properly. |
| Dog urine |
These
spots are indicated by a dead area with a green ring around it. Flush
the area with water as soon as possible after the occurrence. Work
with your dog to use a less conspicuous area. |
| Foot traffic |
Aerate to relieve soil compaction and reseed. Redirect the traffic. If that proves impossible, install a walkway. |
| Scalping (mowing too close) |
Raise the mower blade to the proper cutting height for your variety of turfgrass. Fix high spots in the lawn. |
| Compacted soil |
Aerate to relieve soil compaction. Add organic matter and reseed. |
Stress
| Too much or too little water |
Water only when needed. Do it as early in the day as possible to allow evaporation from grass blades. |
| Too much or too little fertilizer |
Too much causes excessive growth. Too little does not provide enough nutrition
to promote the strong roots, crowns and leaves needed to withstand
disease. Follow the proper feeding schedule for your turfgrass. |
| Excessive pesticide use |
Applying too much insecticide or herbicide can "burn" turfgrass.
Follow the manufacturer's specifications on amount and frequency of application. |
| Hot and cool temperature extremes |
Wait for a change in the weather. Keep your eyes open for early signals of lawn problems. |
Deficiencies
| Nitrogen |
Older grass leaves are light green. Lawn growth slows. The entire lawn
is affected. Fertilize according to the needs of your turfgrass variety. Follow the application instructions carefully. |
| Iron |
New leaves are yellow. The lawn continues to grow. Signs occur in patches. Apply a chellated iron product. |
| Water |
Turfgrass begins to resemble straw. Walking on the lawn leaves footprints in the turf. Water if you are able. |
|
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| Other Things to Look for |
In addition
to injury, stress and deficiencies, there are things other than fungal
infection that may be making your lawn look less than picture perfect.
Damping
off is a fungal infection that is usually limited to newly seeded
areas. When seeds are sown too densely, then fertilized and watered
excessively, the crowded young seedlings collapse and die. The area
will need to be raked and reseeded.
Dormancy
is a natural occurrence. Cool-season grasses will turn brown when the
weather gets hot and/or dry. Warm-season grasses go dormant when cooler
temperatures arrive. They will return to normal conditions when the
weather changes. If dormancy occurs late in the growing season, they
will remain dormant until the next growing season arrives.
Insects
are another possibility. Signals are holes in the leaves and chewed-off
spots. If the turf can be pulled up easily, grubs are the likely culprit
(diseased grass remains firmly rooted). Other lawn-harming insects include
billbugs, chinchbugs, nematodes, mole crickets, mites, leafhoppers and
various larvae. Upon close examination you can see many of these bugs.
 |
Good idea:
The biggest problem you may encounter is identification.
Many of these lawn maladies look alike. Your local Cooperative Extension
Service can help. Locate yours using the USDA's directory. |
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| Lawn Diseases |
When you've eliminated the afflictions mentioned above as possible causes
of lawn discoloration, it's time to review the possibility of disease.
Warm season grasses are most susceptible when temperatures are cooler than normal.
Cool season grasses are at risk when weather is warmer than normal. Other
weather patterns to look for are excessively wet or dry weather and cloudy
or overcast skies (inhibits grasses ability to dry out sufficiently and
means that dew is unable to evaporate). If any of these conditions prevail, then disease is likely.
The list of potential lawn diseases reads like a file of Dick Tracy® villains:(either
that or a science fiction B movie marquee)
Necrotic ring spot, red thread, smut, fairy ring, slime mold, fusarium
patch, dollar spot, snow mold, powdery mildew, anthracnose and rust head
the list of turfgrass maladies.
Identify the problem, find the solution, control the problem and take steps to prevent future occurrences.
| Disease |
Grasses
Affected/Season |
Symptoms |
| Anthracnose |
Any, but primarily bluegrass and centipedegrass.
Summer and fall.
|
Irregular-sized
tan, brown, reddish-brown patches of grass ranging in size from
several inches to several yards. Spots may also be present on grass
blades. Can kill turfgrass if left untreated. |
| Brown
Patch |
Fescue,
bluegrass, centipedegrass, ryegrass, St. Augustinegrass, bentgrass,
and zoysiagrass.
Spring and fall. |
Circular
area of dead grass. The circle may be small or large. The outer
portion may be a "smoky" color. The leaves can be easily
pulled from the stem. Affected areas may have a sunken appearance.
Does not usually cause permanent damage. |
| Dollar spot |
Bentgrass, bermudagrass, ryegrass, bluegrass and fescue.
Late spring, summer and fall. |
Small
(silver dollar-sized) spots of tan/brown grass appear over the lawn.
The spots may merge into large affected areas. Grass blades will
have tan/brown areas on them. Does not usually cause permanent damage.
|
| Fairy ring |
All turfgrasses.
All year. |
Dark
green circle or semi-circle of grass. Area next to it may be a lighter-colored
area of dying grass. Mushrooms may or may not be present.
The entire affected area must be dug up and reseeded. |
| Fusarium blight |
Bluegrass |
Prompted by hot, dry weather, color transitions from light green to brown to tan before dying. |
| Fusarium patch/snow mold |
Cool-season grasses and zoysiagrass.
Fall, winter and spring. |
Fusarium
patch (or pink snow mold) usually occurs after snow melts but can
be caused by cold, wet weather at other times. Starts as greenish
yellow but turns a distinctive pink shade.
Gray
color indicates another snow mold variety that matures under snow
layers during colder winters. It also starts with a yellow tint
but runs grayish white. |
| Leaf spot |
All turfgrasses.
Spring, summer and fall. |
There are leaf spot infections that attack warm- and cool-season grasses.
Grass begins to appear gray, tan or brown. Upon closer examination,
tan, red or purple spots are evident. Can severely thin or kill turfgrass. |
| Necrotic
ring spot/summer patch |
Bluegrass,
bentgrass, bermudagrass and fescue.
Spring,
summer and fall. |
Round,
sunken areas of reddish-tan grass that resembles a bull's eye. The
very similar summer patch takes a more oval or irregular shape. |
| Powdery
mildew |
Bluegrass,
bermudagrass and zoysiagrass.
|
Common
in shady areas, the infection resembles white dust. Blades eventually
turn tan to brown. The damage can be permanent. |
| Pythium
blight |
All
turfgrasses |
Also
called grease spot due to the brown slimy areas it produces. White
patches may also appear. Can spread and kill grass quickly. |
| Red
thread |
Fescue,
bluegrass, ryegrass and bentgrass. |
Red
or faded patches, reddish or pink threads reach from leaf tips to
adjoining leaves. Damage is usually not permanent.
|
| Rust
|
Bluegrass,
bermudagrass, St. Augustinegrass and ryegrass.
Summer
and fall. |
Distinctive
orange rust-like appearance. the spores will attach easily to tools
and clothing. Not usually harmful. |
| Slime
mold |
All
turfgrasses.
Summer
and fall. |
Patches
of white/gray/black deposits on leaves. May appear powdery in early
stages. Forms tiny balls as the infections matures. Slime molds
will not cause permanent damage, but they can inhibit growth if
the infestation is heavy. Remove with a rake, broom or by spraying
with a garden hose. |
| Smut |
Bluegrass
and bentgrass.
Spring
and fall. |
Yellowing
blades turn to black and begin to curl. The entire plant is affected
and is likely to die. |
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| Control |
- To prevent
disease from spreading, remove grass clippings from infected areas.
Avoid walking through the area and clean any tools you have used before
they come in contact with other parts of the lawn.
- Apply
fungicides when needed. Make sure you choose one that's formulated for
the specific disease that's affecting your lawn. Follow the manufacturer's
instructions carefully.
|
NOTE: Frequent
applications of fungicide can have an adverse effect - over time,
many diseases will develop a resistance to them. Spot-treat affected
areas rather than the entire lawn. Alternate fungicidal products to
maintain efficiency. Some fungicidal remedies can be applied only
by a licensed pesticide applicator. |
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