What is a good lawn?
Standards vary, but certainly, a good lawn, besides having a pleasing and appropriate grade, must be composed of fairly close-clipped, fine-textured turf, free of weeds, scars, and bare areas, and it should be green throughout most of the growing season.
In maintaining a lawn of this standard or improving a poor one, eradicating three major groups of pests requires attention.
These are the weeds, the insects, and the fungous diseases. Eradication of weeds and insects will be the subjects of articles in future issues of Horticulture, while this article will consider fungous diseases.
This series aims to provide the homeowner with a greater knowledge of the enemies of his lawn and to point out means to combat them.
Observe Carefully
In order to maintain first-class turf on golf-putting greens, the course superintendent must spend considerable time and money applying fungicides to keep his greens free of disease.
On the other hand, the homeowner can often overlook the same diseases in his lawn without serious damage to his turf.
This is often the wise procedure because the fungus has probably caused its damage before its actual presence is noted, and the costly fungicides are of little value.
Awareness of the Diseases
Nevertheless, the lawn owner should be aware of these diseases and take measures to minimize their damage and to assist his turf in recovering rapidly.
It should be noted at this point that properly cared for bluegrass, and fescue lawns are practically immune to fatal attacks of brown patch and dollar spot, two common diseases of close-clipped Bents.
Snow Mold in Lawns
In early spring, particularly in Northern areas, the homeowner may observe bleached, straw-colored patches in his lawn.
Sometimes these are almost perfect circular areas varying from 1” inch to 2’ feet in diameter, but more often, they have merged to form large, shapeless patches on the lawn.
This condition is caused by at least two fungi, known as snow mold, but appears with or without snow. In the majority of cases, the grass will recover on its own.
Brushing with a stiff broom will remove dead grass, allowing new green shoots to appear more quickly. Raking with a wire rake will be almost as effective.
Dollar Spot Disease
When the weather is moderately warm in late spring, summer, and early autumn, small, brown, circular patches about the size of a silver dollar sometimes show up on the lawn.
While the dew is still on the grass in the morning, this fungus manifests itself as a cobwebby growth clearly visible on the diseased patch.
The disease is known as dollar spot. To obscure the unsightly patches, a light fertilizing of sulfate of ammonia at about two pounds to 1,000 square feet will assist the healthy grass in spreading and thus covering the brown spots.
The sulfate of ammonia must be carefully watered to prevent the burning of healthy grass. To spread it evenly, the sulfate can be mixed with a pailful of dry soil or sprayed on in solution.
If the dollar spot patches continue to increase in numbers, it is recommended that a turf fungicide be applied.
Turf fungicides are available at golf-course supply houses and from seed dealers. Rates are given on the containers.
Homeowners should exercise due care in handling fungicides because many are poisonous.
Moisture Spreads Brown Patch
Large brown patches, a third disease, will appear in warm and humid weather. It is characterized by more or less circular brown patches from 6″ inches to 1′ or 2′ feet in diameter.
A grayish-black “smoke ring” is clearly visible at the brown patch’s circumference. The patches are indeed unsightly.
At their first appearance, all lawn watering should cease, and no water should be applied until the disease has stopped spreading.
The disease will spread much less rapidly if the dew is removed from the grass blades by poling the lawn in the early morning.
A long bamboo pole the length of one used for fishing is switched back and forth across the lawn to knock off the dew.
It is wise to apply a turf fungicide in particularly severe attacks when the disease spreads. A change in weather, however, will usually prevent further spread.
The fungous diseases described above appear as patches on the lawn. A fourth disease attacks the leaves.
Spots and lesions of various colors, from pin-point size to about three-sixteenths of an inch, appear on the blades, or the tips may appear scorched.
Bluegrass Leaf Spot
The lawn should be left uncut from the time the spots first appear until they have finally cleared up.
The two chief diseases causing this condition are bluegrass leaf spot and zonate eye spot.
The former appears in cool weather and the latter in warm wet weather. Sometimes in Spring, the former gives pieces of the lawn a distinct reddish-brown color.
Either will usually disappear as the weather changes. Fungicides appear to be of limited value in their control, but light fertilizing with organic fertilizers will stimulate growth.
Fairy Ring In Old Lawns
A fifth disease of lawns, known as a fairy ring, is found on turf that has been established for years.
Large, dark-green circles as much as 25′ feet in diameter will be observed. Within the circle, the grass is partially destroyed.
Fairy ring is caused by several different types of mushrooms, toadstools and puffballs. These can be seen in warm, wet weather. Since portions of the lawn will be killed, it is necessary to eliminate this growth.
Practical Procedure
A practical procedure is to treat the soil, not the mushrooms. Fairy ring fungi live in the thatch and soil, and in rings where the grass is dying they make the soil shed water. Punch holes through the ring with a hollow-tine aerator, spiking tool or garden fork, apply a soil wetting agent (surfactant), and soak the ring with heavy watering. Water the ring by hand so the rest of the lawn isn’t overwatered.
Remove excess thatch by power raking, avoid letting the soil get too wet or too dry, and fertilize according to your state university extension’s recommendations. Where the ring shows only as a circle of dark green grass, a light feeding of nitrogen or iron will hide it. Fungicides do little once a ring shows, because the trouble comes from a change in the soil that fungicides do not fix.
The Right Height To Clip
Turf diseases are more severe on bent grass lawns than ordinary bluegrass and fescue turf.
Close-clipped bent turf in many localities requires periodic applications of fungicides to remain disease-free. However, most home lawns require fungicide applications only in the most severe cases.
Lawns clipped regularly at 1 ½” inches, fertilized spring and fall, and not overwatered are seldom seriously attacked.
In diagnosing the cause of scars on the lawn, one must be careful not to jump too quickly to conclude that they result from some fungus.
Scars may arise from fertilizer and chemical burns, gasoline and oil drips, a dull or poorly-adjusted mower, or dog excretions, to name a few of the common turf injuries, or they may be the result of insect damage that is much more serious.
44659 by Geoffrey S. Cornish