Turf Diseases

Until about 1955, turf diseases were largely discussed in college courses and in meetings of golf greens keepers. No one denied that they existed, but since their treatment presented problems too difficult for the amateur to solve, the general tendency was to play them down.

Bent grass lawns, which had quite a vogue for a time following the First World War, lost their popularity almost entirely because of the disease problem. Bents are affected in such a dramatic way that anyone would realize that something other than poor nutrition was at fault. Few homeowners realized that the intense discoloration of Common Kentucky Bluegrass in midsummer was only partially due to true dormancy, and that leaf-spot diseases could cause this summer brownout even in the absence of high temperatures.

Today we are willing to face the fact that the greatest single enemy of good turf is disease. There are several major diseases which annually injure and destroy lawns to an extent previously not thought possible. For years it had been accepted that an essential preliminary to any serious attack on such an enemy was an ability to diagnose accurately the symptoms and identify the organisms causing the trouble. This the homeowner cannot be expected to do. The problem has confronted turf men for years, and a number of chemicals have been developed to treat specific diseases. Perhaps it might be said more accurately that they were manufactured to treat groups of diseases, since one chemical may be effective against more than one organism. Unfortunately, for years no cure-all could be found that would work on all diseases equally well and thus eliminate the need for accurate diagnosis.

There are about five general types of disease, each requiring a rather specific remedy.

One For All

A break in the bleak picture came in the early 195O's. I noticed in trials at various turf stations a new type of material which showed remarkable results on a wide variety of diseases. This was later introduced to the golf course trade as Kromad, as I mentioned briefly in an earlier chapter. With one or two exceptions, this chemical compound proved able to control practically all turf diseases. Its effectiveness was due to the fact that a way had been found to combine five different chemicals in a single product, so that it would be effective against all types of organisms. The product worked best when used as a preventive treatment, but would actually cure even severe cases of some common turf ills.

I was so impressed by its showing that I set up an experiment, using the back lawn of my home (which I planned to remake anyway) as a guinea pig. My first need was for a good case of turf diseases. I had no trouble inoculating the lawn with helmintho-sporium and septoria leaf spots, because the lawn contained a high percentage of Common Kentucky Bluegrass, which showed some infection each summer.

I proceeded to do everything I had learned not to do. I overfed the turf with a heavy top dressing of sludge. I used a rotary mower to chew up the clippings and deposit them on the turf. I watered heavily late at night.

By mid-July the entire lawn looked as though it had been splashed with acid. Large areas were killed out and all the grass was turning yellow. The only section that showed no disease was the one that I had treated the same as the rest of the lawn, but had also sprayed four times with Kromad. All summer long the untreated area remained pockmarked with dead and dying grass. While I could find a few flecks of disease on grass blades in the treated area, these never expanded beyond their original size.

Here was a dramatic instance of a specific control for two major types of lawn diseases. As a result of that test, and of investigations of turf men throughout the country, a modified form of Kromad for home-lawn use was introduced under the name Formula Z.

This, like its commercial counterpart, has proved highly effective when used as a preventive, and has also been an excellent cure when disease has already attacked a lawn.

Nine Types

The danger in overemphasizing disease is that even a bare description of the various organisms that attack turf grasses sounds so ominous. Actually, grasses are amazingly tough and manage to survive under infection to a remarkable degree.

Nine diseases most likely to attack home lawns are described below, with recommended treatments. While these descriptions will be helpful in identifying the specific fungus attacking a lawn, they will not be necessary where a general preventive program is used. For this program, I recommend an application of either Kromad or Formula Z (two readily available compound turf fungicides) at the rate recommended on the package for preventive spraying. Let me add that these directions may call for more frequent use than I do, but these directions need be followed only where a high degree of control is wanted, as on golf greens. On the home lawn, four sprays spaced ten days apart, starting about the time peonies begin to bloom, will result in practical control. Under this program, a few blades of grass may show spotting or staining, but there will be no allover discoloring of the turf, in ninety-nine out of one hundred cases.

This will be possible, however, only when the precautions I have stressed are observed, namely, a clean soil surface without a damp mass of debris, and a well-fed lawn that is not overwatered. If these conditions are maintained, the lawn will be able to resist the development of harmful organisms, often without spraying.

Not every lawn can be managed so as to provide complete protection in this way, and so the handling of severe invasions on untreated lawns is also considered below.

FADING-OUT, Black Mold, Curvularia spp.

This disease seems to be increasing in virulence or perhaps it is being better diagnosed today. Lawn looks unthrifty, either with general allover yellowing, or fading out of grass in small areas. These small areas may melt together to produce irregular dead patches.

When examined under a magnifying glass before the entire area is attacked, tips of individual grass blades are tan or yellow, with a browner area at the base, covered with dark spores that are produced on clusters on stalks.

Grasses Attacked: All commonly used turf grasses except zoysias are attacked; general throughout the United States.

Control: Requires more drastic treatment than diseases which can be controlled by the four-time spraying recommended. Maintain lawn in vigorous growing condition with good nutrition. Remove all duff, clippings, etc., and avoid use of organic fertilizers to prevent buildup of a mat of organic matter on surface. Use Formula Z or Kromad as preventive treatment, 2 ounces to 1,000 square feet every five to seven days from time apple blossoms drop petals until early fall. If disease occurs when preventive schedule was not followed, use same dosage every two or three days until disease is under control. Several weeks may be needed before grass again grows vigorously.

MELTING-OUT, Leaf Spot, Leaf Mold, Helminthosporium spp.

The most obvious signs are bright yellow leaf blades or distinct yellow-brown leaf spots with darker outlines around spots. May also attack roots, leaf sheath and stems. Often damages turf severely (particularly common Kentucky bluegrass) before it is recognized.

Grasses Attacked: All commonly-used turf grasses except zoysias are attacked. Most severe on old forms of fescue and Common Kentucky Bluegrass.

Control: Four-stage treatment recommended will give good control. Where disease gains a head-start, spray every three days for two weeks to destroy active spores. Because it seriously affects the turf by the time it is visible to the naked eye, preventive treatment is recommended where this disease has occurred in the past.

RED THREAD, Pink Patch, Cortichim fudforme

With a glass, the pinkish web can be seen attacking the leaf sheaths. This will often bridge from leaf to leaf, spreading the disease. Areas attacked will be about 2 to IS inches across. The dried fungus resembles coral-colored thread.

Grasses Attacked: In cooler, humid regions, this will attack all grasses except zoysias. Merion quite resistant when well fed.

Control: Four applications as recommended give practical control in all except severe cases. Where grass is attacked and no preventive treatment was used, two applications three days apart will check it.

RUST (Leaf and Stem), Puccinia graminis

Rust attacks in a dramatic way: affected grasses are covered with a reddish rust that will stain shoes and clothing. Affected plants shrivel and die.

Grasses Attacked: Most species, including all bluegrasses.

Control: See discussion under Merion bluegrass for control applicable to all grasses attacked by rust.

DOLLAR SPOT, Sclerotinia homoeocarpa

Affected turf is peppered with bleached straw-colored areas, about 2 inches across. These gradually run together and affect larger areas. When dew is on the grass, a fine cobweb-like growth can be seen covering these spots.

Grasses Attacked: Bents are most severely affected, other grasses less so.

Control: Regular four-part application gives practical control. For badly attacked lawns, two applications three days apart will check growth of fungus.

COPPER SPOT, Gloeocercospora sorghi

Sometimes confused with Red Thread but Copper Spot spores will stain a white cloth rubbed over affected areas.

Grasses Attacked: All strains of bent, particularly in humid, cool areas along the seacoast.

Control: Preventive four-application treatment recommended. For cleaning up severe infections, use two applications three days apart.

BROWN PATCH, Rhizoctonia solani

A conspicuous smoke ring forms on infected grasses. Small at first, rings may spread to cover several feet. A light infestation may not form a ring, but grass blades will be darkened, giving a slightly smoky appearance to turf. Blades turn dull tan when dead.

Grasses Attacked: Bents in particular but all other turf grasses except zoysias may show symptoms.

Control: Four-stage preventive schedule. For severe attacks, use every three days until spread of rings is stopped.

ANTHRACNOSE, Leaf Spot, Leaf Blight, Collectotrichum sp.

Blades become spotted, yellow at first but darkening until they die. Dark "spines" form in the spots, and can be seen with a magnifier.

Grasses Attacked: Particularly bad on clover, fescues and bents also severely affected, bluegrasses less so.

Control: No reliable control has been developed other than good culture. The regular four-stage spray treatment does reduce the severity of the disease, but is not entirely effective.

COTTONY BLIGHT, Grease Spot, Fire Streak, Damping-Off, Pythium spp.

This is worst in wet weather when the white cottony fungus can be seen on the grass blades. Later, blades turn dark and have a typical "greasy" appearance. Fungus is spread by run-off water, so if an attack starts on high spots, lower areas are soon infected. Young grass is particularly sensitive and may kill out entirely.

Grasses Attacked: All; worst on poorly drained soils.

Control: Be sure lawn has good drainage and do not overwater. If soil is acid, apply 2 # hydrated lime to 1,000 square feet and and water in lightly.

Remember that chemical treatment can only be a crutch. The best way to avoid disease is to keep the lawn healthy by assuring proper growing conditions. It is important, too, to make sure that soil insects or malnutrition is not responsible for the lawn's decline; disease and insect effects sometimes are superficially similar. At the same time, do not underestimate the danger of turf fungus infections: they are much more prevalent than most people think.

Snow Mold

Snow mold rates a discussion of its own. Symptoms vary greatly from lawn to lawn. Fortunately, snow mold is fairly easy to identify because it occurs at a time when no other organisms are at work.

Suspect that snow mold is present when, in early spring (soon after snow melts) dead-looking patches of grass appear in the turf. These may vary in color from near-white through light tan to pinkish buff. If the infection is light, the grass plant crowns may still be alive, but otherwise the dead grass can be pulled out by the handful.

Then about all that can be done is to rake out the dead grass and treat with either Tersan or Formula Z. This is not done to kill the spores of snow mold, which have done their damage, but because if one fungus organism found conditions favorable for growth, the chances are that other lethal spores are also present. The area may be re-seeded immediately after treatment.

To repeat: the real remedy is prevention. Never follow the practice of grinding up dead leaves and working them into the lawn as a mulch. These form a damp, fluffy overcoat which is just as effective as a layer of snow in protecting the snow mold organisms while they do their deadly work. Also, in fall, keep mowing the grass as long as it keeps growing. Pick up all grass clippings. Do not use an organic fertilizer.

Until the lawn-owner can be sure he has cleaned up the conditions which favored the development of this trouble, it will be well to apply a fungicide (either Tersan or Formula Z) before the ground freezes for the winter. One application should be enough: there will be no fresh spores to reinfect the area until the following spring.

Chips Off The Chapter

1. The intense cultivation practices employed by modern lawn-owners have resulted in finer turf; but, as usual when nature's patterns are disturbed, these practices have created some new troubles and intensified some old problems, too. Turf diseases certainly are near if not at the top of the lawn enemy list.
2. Fortunately, however, science never sleeps. New and more powerful fungicide chemicals are being developed. The latest boon are the all- purpose compounds which are able to control a variety of fungus diseases.
3. These products are effective against snow mold, a disease that many authorities regard as the chief lawn hazard. The all-purpose fungicides, however, make it unnecessary for the modern gardener to worry about diagnosing snow mold or any other lawn disease.

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