Lawn Disease Articles

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Dollar Spots
Necrotic Ring Spots and Patches
Winter Mold Damage
Red Thread
Rust

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Dollar Spots

Don’t let dollar spots ruin your lawns appearance.

Dollar spot disease of turfgrass is named for the straw-colored, silver dollar-sized spots that appear on golf greens. The disease causes larger spots on higher cut turfgrass. Dollar spot disease of lawns usually appears in somewhat irregular circles 3 to 6 inches in diameter. If the spots coalesce, a more general blight may be observed.

A more certain diagnosis of this disease can be made by examining individual leaves. The typical dollar spot lesion is straw colored and girdles the entire leaf blade. The top and bottom borders of the lesion are usually dark reddish-brown. The lesion often has an hourglass shape. If the infected grass is examined in the morning while dew is still present, the white web-like bacterial mass of the fungus may be observed.

Dollar spot is most common in early summer, late summer, and early fall in humid weather with warm days and cool nights. Dollar spot is less prominent in very hot weather.

Usually, only the leaf blades become infected. Dollar spot rarely causes severe damage on lawn grasses. All turfgrasses are susceptible to dollar spot disease, but some Kentucky bluegrass cultivars are relatively resistant.

Dollar spot disease usually occurs on lawns that are nitrogen-deficient. Application of fertilizer will stimulate growth, so the infected leaf blades may be mowed off. Sufficient water should be applied when rainfall is sparse. Thick thatch stresses the turfgrass and increases dollar spot. If dollar spot is present in the lawn, it is best to mow only when the grass is dry to prevent spreading the fungus, and to remove the clippings. Mow the grass high and do not remove more than 1/3 of the leaf blade at a single cutting to avoid stress. Water deeply and infrequently. Light sprinklings, especially late in the day, will increase disease. Increase air movement by pruning trees and shrubs so the grass will dry more quickly.

Dollar spot disease responds readily to fungicides, but application of fertilizer and attention to watering practices is usually sufficient to minimize the disease. Dollar spot rarely causes sufficient injury to lawns to justify the use of fungicides.

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Necrotic Ring Spots and Patches

Despite the different names, these two diseases have essentially identical symptoms. As the names suggest, symptoms of necrotic ring spot and patch disease include rings and circular patches of dead or dying turfgrass. Sometimes there is a center of relatively healthy grass in the center of the patch. In addition, weeds or non-susceptible turfgrass species may colonize the centers of patches where the diseased turfgrass has died. Both diseases are most severe on Kentucky bluegrass lawns that were seeded or sodded two to four years previously. Symptoms often become obvious in warm to hot, dry weather when the lawn becomes stressed. Areas along driveways, walls, sidewalks and other places that are heat-stressed or water-stressed will often show symptoms first.

When the disease first begins, rings or patches of blue-green wilting turfgrass will develop in the heat of the day. With time, the patches may grow together, obscuring the circular pattern of the damage. In lawns containing mixed turfgrass species, symptoms are not as distinct, but circular patterns of diseased turfgrass are generally present. Both diseases are caused by root-infecting fungi. Above-ground symptoms may be confused with other diseases such as brown patch disease. However, the roots and crowns of plants with necrotic ring spot or summer patch will be brown to black and rotted.

The fungi produces very similar dark brown, microscopic threadlike filaments that are found along the roots, crowns, and rhizomes of turf-grass. In both diseases, infection occurs before symptoms appear. The fungi spread from plant to plant and travel longer distances when feet and mowers spread spores, soil or infected plant parts.

Severe damage is most common on sodded Kentucky bluegrass lawns that have been planted on poorly prepared sites with poor drainage and compacted soil. It is important to properly prepare a lawn site with well-drained topsoil, correct pH, and balanced fertility. When possible, plant Kentucky bluegrass cultivars with resistance to these diseases or consider using sod with perennial ryegrass in the mix. This will help mask areas of infection. Similarly, overseeding with resistant cultivars and perennial ryegrass will improve already damaged areas. Once an area has been seeded or sodded, avoid stressful growing conditions.

There are also simple preventative measures you can take to lessen the severity of the disease. You should water deeply without causing moisture stress. Avoid early evening watering. Mow frequently to the recommended mowing height. It would be a good idea to fertilize to maintain appropriate nutrient levels and aerate to relieve compacted soils. A double aeration at right angles every spring and fall will reduce thatch layer and stimulate a deeper, healthier root system.

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Winter Mold Damage

As snow melts each spring, lawns often show damage from the winter. Mold Damage can be very destructive to lawns. There are preventative measures to take to minimize the damage.

Snow mold damage appears in the spring when the snow melts creating visually unattractive matted, crusty looking areas on your lawn. As they dry out throughout the season, the infected areas may remain in the form of weak or even dead turf. If your grass is dead then you will have to reseed, which can become costly if it is an annual problem.

Severity of the mold may vary yearly, but the areas that are infected may weaken and spread. Fertilization programs are offered to lessen the risk of snow mold. A simple solution to prevent mold is removing dense vegetation bordering the problem area of the lawn and mowing until the lawn is dormant in the fall.

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Red Thread

Don’t let red thread disease take over your lawn.

Red Thread affects blue grasses, fescues, ryegrasses and bent grasses. The disease is mostly cosmetic and does not infect the crown or roots. Symptoms include the grass blades dieing from the leaf tip downward. Irregular circular areas of dead leaves that are tan in color. Circles vary from 4-8 inches in diameter. The disease development is most common in the spring and fall during periods of intense moisture in slow growing turf's that are deficient in nitrogen and moisture and soils that are compacted.

Water deeply and infrequently without causing moisture stress. Avoid early evening watering. Mow frequently to recommended mowing height. Incorporate management practices that encourage leaf growth. Fertilize to maintain appropriate nutrient levels. Aerate to relieve compacted soils. Seed thinned turf with disease resistant cultivars

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Rust

Don’t let rust disease ruin your lawns appearance.

Rust diseases affect all turf grass species. Severe infection thins the turf but does not attack the roots. Early symptoms appear as yellow flecks on leaf blades. As the disease advances, yellow, orange or dark red postludes split open. The colored powdery spores will rub off on your fingers. Severely infected lawns will turn an orange/brown color and show signs of thinning. There are some things that promote disease. Those are leaf wetness from long evening dew periods, Hot and dry conditions, and slow growing turf. Outbreaks are most common in late summer or early fall.

There are preventative measures you can take to lessen the severity of the disease. You should water deeply without causing moisture stress. Avoid early evening watering. Mow frequently to the recommended mowing height. Incorporate management practices that encourage leaf growth. It would be a good idea to fertilize to maintain appropriate nutrient levels and aerate to relieve compacted soils. Seed thinned turf with disease resistant cultivars.

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