Lawn DiseaseTips


Lawn Diseases

To avoid disease, provide the best lawn care you can by giving the grass just the right amount of water and fertilizer and keeping the soil open and loose.

If grass blades are wet for long periods or you water daily so your soil never dries out, you lawn is more likely to be infected. Water properly (at least ½ inch twice a week) in the early morning so that the grass blades can dry during the day.

Thatch is a breeding ground for pathogens. Aerate to reduce thatch, relieve compaction, and improve drainage.

Necrotic ring spot (NRS) is a perennial disease of Kentucky bluegrass. NRS results in circular or doughnut-shaped patches of dead grass. Symptoms often develop in late summer. NRS can be controlled by the use of resistant varieties, which includes ScienTurfic Sod, good turf management practices, and fungicide applications.

Ascochyta leaf blight has become a common problem on Kentucky bluegrass lawns in Colorado. Large uniform areas of affected turf will turn straw-colored. Leaves usually start dying back from the tips. Ascochyta can occur throughout the growing season but is more prevalent in the spring when there are extended wet periods. The first line of defense against Ascochyta leaf blight is to manage the turf properly.

Dollar spot, a major turfgrass disease in Colorado, often is confused with Ascochyta leaf blight. Turfgrass under stress is more susceptible to infection. Proper lawn management, such as aeration, and proper watering and fertilization will reduce dollar spot problems. Use fungicides only in situations with recurrent dollar spot problems. Ensure nitrogen levels are sufficient to sustain a moderate rate of shoot growth.

Heavy rains, prolonged rainy periods, or excess watering often encourage the growth of mushrooms (toadstools) in home lawns and other turf areas. Most often, the mushrooms will appear randomly across a new lawn because of the extra water required to get the sod to root in. Once the moisture in the soil reduces, the mushrooms should stop appearing. Since young children and pets may be tempted to eat mushrooms, remove the obvious fungal structures by raking, mowing, or hand picking to avoid the possibility of poisoning or illness.

Mushrooms may grow in a circle around grass forming “fairy rings.” Construction debris, old tree roots, and stumps encourage their growth. Spring and fall aeration along with several applications of a few ounces of dish washing soap dissolved in a gallon of water on the ring may make the ring less noticeable. No Fungicides control fairy rings.

Gray and Pink Snow Mold appear as fluffy white to salmon pink mixture of fungal strands & spores visible at the edge of the patch. Usually 6-24” in diameter throughout the lawn or side-by-side. Turfgrasses are very prone to diseases when snow or ice cover persists for long periods of time in the winter, thus trapping moisture and preventing sunlight in the turf. Lightly rake the matted turf. This will increase air circulation around the grass plants and allow the grass to grow and fill in. As soon as the soil begins to thaw out, it is a good idea to aerate the turf to encourage root and rhizome growth.

Small to large areas of the lawn, especially in shady to partial shade locations, show symptoms of grass being dusted with flour or talc. As the disease progresses, turfgrass blades wither and die.

Powdery mildew is caused by a fungus. It is not considered to be a serious disease on turf, but is more of an esthetic problem. Sever outbreaks tend to occur in shaded areas in late spring through fall. High humidity and temperatures above 60 degrees favor this disease.

Increase sunlight penetration by pruning trees and shrubs to allow more light to infected areas. Adjust water so that areas prone to the disease will stay drier. Fungicides can be applied as a preventative before the disease becomes established. Blades already infected will not benefit from chemical treatments.

Brown patch commonly starts as a small spot and can quickly spread outwards in a circular or horseshoe pattern up to a couple of feet wide. Often times, while expanding outwards, the inside of the circle will recover, leaving the brown areas resembling a smoke-ring. The best prevention for brown patch is to aerate often, reduce shade to effected areas, and follow a fertilization schedule to help prevent fertilization with excess amounts of nitrogen.

Rust gets its name from the orange, "rusty" appearance it gives leaf blades. Rust tends to flourish in conditions of morning dew, shade, high soil compaction, and low-fertility. The best way to check for rust problems is by taking a white tissue or paper towel and rubbing a few grass blades through it. If an orange color remains, then it's usually rust. The best prevention for rust is to aerate your lawn, water well in the morning hours, reduce shade to grass, mow more frequently while bagging the grass, and by following a fertilization schedule to help increase the amount of nitrogen levels in your lawn.

Red thread is most common to Fescues, Ryegrasses, and Kentucky Bluegrasses during times of moist and cool weather. Red Thread gets its name from the pinkish-red threads that form around the leaf blades and bind them together. Eventually, the affected grass will turn brown and the red treads will be most visible when wet. The best prevention for red thread is to aerate often and remove thatch. Mowing to proper levels, reducing shade on lawn, and following a fertilization schedule can also help.