A thorough diagnosis will require an in-depth analysis of many factors. While water and fertilizer are first thought of they are not always the culprits. The problem may stem from a bad choice in the original grass seed, a car parking in a certain spot in the winter that transfers road salt onto the lawn, a skunk digging for grubs, a chemical from a wood stain on the house or a fence getting to the lawn, or a plethora of other problems.
Often lab samples, a great deal of time observing, and further researching are required as the naked eye just can’t see certain things.
Below is a list of common lawn problem causers. This list is not exclusive but should provide a start to your diagnosing needs.
Length of Cut
Mowing, although a common practice, is often very abusive and misunderstood. Bluegrass and fescues should not be mowed shorter than 1.5-2 inches. Shorter grass reduces the surface area (the food producer) so that the plant may not have the ability to produce the food it needs. It will then draw more from the roots. Although sustainable for some time, eventually the practice will catch up for the plant. It will be especially noticeable in hot, dry weather.
Infrequent mowing (generally less than once week), which has become fairly standard with new mower technology, cuts off too much of the blade at once. This can shock plants and trigger them to use root reserves rather than usual photosynthetic production. By standard rule no more than 1/3 of the blade should be removed at once. Also excessive clippings left on the grass can smother it which can harm the grass or even kill it. This also creates an incubator for fugal and diseases to develop.
If the grass has a gray to brown tint after mowing it is a good sign that your blades need to be sharpened or replaced. This is more common with rotary mowers but can also occur with reel mowers. The problem is that the grass is torn, split, or shredded instead of being cut sharply.
Scalping most frequently happens when terraces or hills are cut cross-ways rather than with in the direction of the terrace. It can also occur on non-level or corrugated slopes where one wheel can drop lower and lower the blade on one side.
Turf areas that are always cut in the same pattern can develop ridges running the same direction as the wheels travel. This can be eliminated by mowing in different patterns. This will also help control runners of creeping grass and help prevent the buildup of thatch.
Lack of Fertilizer Overlap
Although missing areas of lawn with fertilizer might not be considered actual damage it does result in a weird looking lawn. Fertilized areas will be dark green while the missed areas will be a pale green, or even yellow shade. Fertilizer doesn’t leach much so it is important to apply it evenly on the entire turf area.
Fertilizer can burn the lawn if applied excessively (much less common than believed). Chances of burn are increased if applied with the grass is wet and it isn’t water soon after. (Some types of fertilizer require grass to be wet during application, so read the instructions first.) Nitrogen is the fertilizer element most likely to cause a burn. Most fertilizer burns occur in a small area where fertilizer is spilled or comes out the spreader in a pile.
Grass may become pale green or yellow, and plant growth may be stunted. Often this condition is due to lack of nitrogen. If a nitrogen fertilizer application does not correct this condition, it is very likely that the cause is iron deficiency. An application of iron sulfate or chelated iron on grass with iron deficiency should result in greener grass within a day of application.
Even selective herbicides (2,4-D for example) or other dandelion/broad-leaf weed killers used to control specific weeds may hurt or kill grass if applied at rates exceeding recommendations. Don’t exceed the manufactures recommended rates and you might have to actually measure as most people get in trouble pouring from a bottle trying to guess how much 3 oz is. Chemicals sprayed off of the lawn can even leach into the lawn. This is common when the lawn is lower in elevation than the area sprayed. Rain or irrigation water could also cause these chemicals to move so be careful when spraying even away from the grass.
Over or under watering a lawn will have negative effects. This is a whole topic in and of itself and is discussed in more depth in a previous blog post. Not only will over watering hit your pocket book but it can also cause a surface crust to develop which will make watering harder and less efficient in the future. Over watering will cause root growth to stunt and encourage weed germination and disease development. Frequent shallow watering may keep upper soil layers constantly wet. This condition encourages shallow root growth and promotes weak turf which is susceptible to disease and insect attack as well as damage from traffic.
Confined Dry Spots
Dead or injured spots often develop in turf areas because of lack of water, even though surrounding turf shows no drought injury. (Lack of water doesn’t always mean it isn’t being watered or that the sprinklers aren’t working properly.) Buried debris such as concrete, rocks, bricks, or , construction debris, or gravel may result in a thin soil in the area. This soil layer has a low water-holding capacity and dries out very quickly and therefore needs water more frequently and will never develop deep roots. Thatch or clay soil could also cause problems with water absorption.
In hot weather heavy foot traffic on bluegrass or fine-leaved fescue turf usually indicates that the turf has reached its wilting point and must be watered to maintain green color. When watering, soak the soil deeply; then don’t water again until the turf shows signs of wilting.
A different type of foot printing may be observed in late winter or early spring. The turf may be injured if it is walked on when grass blades are frozen or frosted. Walking on these plants can rupture the cells causing plants to die.
Winterkill happens most frequently during the late winter months. Damage occurs most on high, exposed areas that frequently hold little snow cover and are subjected to strong, drying winds. In late winter the top inch or two of soil often thaws; air temperatures are favorable for grass growth, but roots embedded in a still frozen ground are unable to take up enough water (if any) to satisfy the plant’s needs. The turf, therefore, dies from lack of moisture. This can occur on a smaller scale where grass doesn’t die, but when late spring or summer heat arrives the roots are so damaged and shallow that there is virtually no heat tolerance and the grass dies. (This is common in Cedar City and often misdiagnosed as a sprinkler problem in the summer as the grass just appears to not be getting enough water.
Disease and Fungus Problems
A number of leafspot diseases are particularly severe on many Kentucky bluegrasses and fine-leaved fescues. The most obvious disease symptoms are circular to elongated spots on the leaves. These spots have brown or straw-colored centers and prominent reddish-black to brown borders. Leaves, stems, crowns, and roots may be affected, often causing considerable thinning of the turf. These diseases first occur on the leaves during cool, wet weather. If not checked by changes in weather conditions or the application of chemical fungicides, the disease may move into the plants’ crowns and roots, causing considerable damage throughout the entire summer.
Some Kentucky bluegrass varieties are extremely susceptible to Fusarium blight, especially if nitrogen availability is high. The disease occurs most frequently during hot weather when the plants are under moisture stress. Circular to irregular patches of light green grass, 2 to 8 inches across are the first symptoms. These patches quickly turn to a reddish-brown, then to tan, and finally to a light straw color. Plants normally die during the reddish-brown stage. Apply systemic fungicides immediately after first symptoms appear to reduce disease severity.
In late summer, powdery mildew often develops on Kentucky bluegrasses, especially Merion Kentucky bluegrass growing in shaded areas. Although the white powdery substance deposited on the leaves is unsightly, it normally does not cause serious damage unless it persists for a long time. Powdery mildew can be controlled with Acti-dione fungicide applications, although the best solution is to plant more shade-tolerant grasses in these areas.
Fairy rings may appear as mushroom rings or as dark green rings of vigorously growing turf varying from a few inches to many feet in diameter. Fairy ring is caused by fungi living on decaying organic matter such as stumps, logs, or scrap lumber from building construction buried in the soil. The fungus grows out radially. Nitrogen from the mycelium of the fungus is released, stimulating growth and causing a dark green ring. During dry periods this stimulated succulent growth may die from lack of moisture. There is no effective chemical control. During dry periods keep the fairy ring well watered to prevent loss of turf from moisture stress.
Slime molds are nonparasitic fungi that live on decaying soil organic matter. During wet summer periods these fungi develop on grass blades, forming yellow to gray jelly-like structures which later mature into gray to black spore masses. These masses may damage the grass by shading or smothering. Normally, slime mold will disappear during dry weather. Brushing infested areas with a stiff broom will at least temporarily remove the unsightly condition. If wet weather favorable to slime mold persists, control the mold by applying any good turf fungicide.
Toadstools and Mushrooms
Heavy infestations of toadstools and/or mushrooms often occur in turfgrass areas. These are saprophytic fungi living on dead organic matter in the soil. They are most prevalent where trees have been removed without complete removal of the tree roots. There is no adequate control, and these organisms will continue to appear, especially during wet periods, as long as there is adequate organic matter in the soil.
Gray snowmold, a true snowmold, occurs under snow cover. The affected grass forms a mat or crust of leaves a few inches to many feet in diameter and may show a white to gray mold with tiny black fruiting bodies (sclerotia) imbedded in the leaf tissue. Thorough brushing or raking to break this crust usually results in grass recovery. Pink snowmold occurs when the temperature is approximately 40 to 60°F and abundant moisture is available. Pink snowmold is more damaging than gray snowmold and often results in death of the turf. To control snowmolds fungicides must be applied in late fall or early winter and again in early spring. Consult your county agricultural Extension office for the latest recommended control materials.
Yellowish spots that rapidly turn into brown, dead areas may be an indication of chinch bug damage. Chinch bugs are sucking insects which concentrate in limited areas and feed on the plants until they extract all available juice. The bugs then work outward from the centers of infestation, destroying grass as they advance. Chinch bugs develop best in dry weather, and injury is always more severe in hot, dry summers. They prefer high, dry locations exposed to direct sunlight. Chinch bugs can be controlled by repeated applications of diazinon, aspon, or chlorpyrifos.
Grubs of the Japanese beetle, May or June beetle, northern masked chafer, European chafer, green June beetle, Oriental beetle, and Asiatic garden beetle may severely damage turf. These grubs feed on roots of the grass and when abundant may completely sever the turf from the soil so that it can be rolled up like a carpet. Grubs can be controlled with chlorpyrifos, diazinon or trichlorfon (Dylox, Proxyl). In severely damaged areas the severed turf should be raked off prior to insecticide application and reseeding.
The presence of small, buff colored moths flying above the turf in a zig-zag pattern during the evening hours is a sign of sod webworm infestation. The moths, harmless to turf, are the adult stage of the webworm; immature larvae and the webworm caterpillars damage the turf. The sod webworm constructs “silken lined” tunnels in the soil; webworms emerge during the evening or night to feed by clipping off grass blades at the soil surface. During the daylight they hide in the tunnels. The first symptoms of damage are small irregular patches of dead grass which enlarge as damaged areas coalesce. Carbaryl (Sevin), chlorpyrifos, or trichlorfon applied in late afternoon or early evening will control sod webworm.
Turfgrass areas infested with mole runs or tunnels become unsightly, uneven, and difficult to mow. Contrary to common belief, attempting to kill the moles by poison bait or mole traps is not the best solution. The moles are there because the soil is infested with grubs, a favorite food. Treatment with an approved insecticide for grub control will cause the moles to abandon the area as their food source is exhausted.
Skunks may damage turf by rooting for grubs. The solution, as in mole control, is to eliminate the grubs with an appropriate insecticide.
The effect of dog urine on turfgrasses depends upon the amount of soluble salts in the urine. When soluble salt concentration is high, turf in the affected area will be killed. Damaged areas are usually round or slightly irregular in shape and variable in size. Nitrogen from urine with lower salt concentration may stimulate vigorous dark green growth.
During periods of heavy snowfall (particularly if snow comes before the soil is frozen) mice may make runways in the turf under the snow. These runways are on the surface of the turf rather than under the turf as with moles, and normally are most severe in heavily matted turf where snow tends to accumulate in pockets. Mice have been known to feed on tender plants along the run.
Soils of poor physical condition or those subjected to play or heavy traffic (especially when wet) form an impervious surface layer which prevents water infiltration, nutrient penetration, and gaseous exchange between the soil and the atmosphere. Under these conditions turfgrasses may thin out and be replaced by weeds such as knotweed, which flourish on compacted soils. Aerators will remove soil plugs or cores, creating an artificial system of large pores which will permit moisture, nutrients, and air to enter the soil and help reduce the compacted condition.
Damage from winter scald may occur where poor drainage permits pooled water to freeze. Heat from the sun shining through this layer of ice can initiate growth. As no gaseous exchange can occur through the ice, some turf may die. The only solution is to correct the drainage problem.
Poorly drained areas subject to water pooling for short periods may be seriously damaged by scald. Summer thunderstorms may release large amounts of water in a short period; if the storm is followed by clearing and a hot sun, the sun’s action on the pooled water will produce anaerobic conditions which cause damage. As with winter scald, the only practical solution is to improve drainage.
Layers of partially decomposed leaves, stems, and roots at the soil surface will build up over a period of years. Thatch decreases turfgrass vigor by restricting the movement of water, air, fertilizers, and pesticides into the soil. Roots are normally quite shallow under thatch conditions, increasing the danger of drought damage to the plant. Disease attacks may be accentuated by thatch accumulations. Mechanical thatching equipment should be used in spring or fall when grass recovery is rapid. It is best to remove thatch accumulations in several treatments rather than at one time.
Trees, especially those with shallow feeder roots, compete with grass for water, nutrients, and light. Where there is heavy shade and/or many surface roots, it is best to plant a ground cover such as pachysandra, myrtle, or ivy rather than attempt to grow grass. Where competition is less severe, improve turf by the following methods: (1) use shade-tolerant grasses such as the fescues. (2) fertilize grass at 1½ to 2 times the normal rate; (3) fertilize trees; (4) water deeply and infrequently; (5) maintain a soil pH favorable to the grass; (6) prune tree branches and roots as much as possible; and (7) mow the grass higher than normal.
Many turf problems can be traced to the original seed mixture – either a poor quality mixture, or a mixture not appropriate for the particular area. Kentucky bluegrasses are unsatisfactory for use in shaded areas but are excellent in open sun. Fine fescues are well adapted to shade conditions. Tall fescue, when seeded alone, is an excellent play field or utility grass but should not be used in seed mixtures. Bentgrass requires intensive management and, therefore, is not compatible with Kentucky bluegrass and fine fescues. Select a grass seed mixture according to environmental conditions, use of the area, and the planned management program.
Gasoline and Oil
Servicing or refueling mowers or other power equipment on the turfgrass area may cause considerable damage from gasoline or oil spillage. Because it is not immediately apparent, this type of damage may be incorrectly diagnosed as disease, insect damage, or dog injury. If the soil is saturated (especially with oil) it may be some time before reseeding will be successful. To avoid the problem always service or refuel power equipment off the turfgrass area.
Turf damage often appears in late winter or early spring in grass plots between the sidewalk and the street. Frequently this damage is due to high soil salt concentration from salt materials used for de-icing highways and streets. The same type of damage may be found adjacent to sidewalks if salt or a soluble nitrogen fertilizer has been used for ice control. Normally, spring rains will leach salt concentrations below the grass root zone, permitting reseeding of these areas.
As you can see there are many lawn issues, many of which have similar symptoms but are very different in nature and treatment. Feel free to bookmark this page and come back to it as a reference to help you properly diagnose your lawn problems. We appreciate you checking out our blog.