Tuff Turf Molebusters needs your help with calling when you see problems with your grass.  We can identify diseases for you and suggest treatment. They will also help you understand the characteristics and potential such diseases can have on your lawn.

These are some of the most common lawn diseases in the Western Michigan area.

Dollar Spot

Fungus: Sclerotinia homeocarpa

Symptoms: lesions are light tan with a reddish brown border and may extend downward from the leaf tip to an inch or more in length. Stems may also be affected. In early morning, when grass is wet, wisps of white fungus mycelium or threads may be observed on diseased turf. The name, dollar spot, was derived from the usual occurrence of dead, bleached spots in bentgrass putting green turf, about the size of a silver dollar. Spots rarely enlarge beyond that size. However, if not controlled with fungicides, spots become so numerous that the individual spots overlap to produce large, irregular areas of dead turf.

Grasses susceptible: Annual bluegrass, Italian ryegrass, Kentucky bluegrass, red fescue, redtop, sheep fescue, and velvet bentgrass.

Conditions favoring disease: Moderate temperature (60 degrees to 80 degrees F) and excess moisture, excess mat and thatch favor dollar spot. Turf deficient in nitrogen tends to be more susceptible to dollar spot than turf adequately fertilized with nitrogen.

Red Thread or Pink Patch

Fungus: Corticium fuciforme     

Symptoms: Coral-pink to red fungus strands may be seen on leaves and leaf sheaths binding leaves together. Affected turf areas are usually more or less circular and vary from 2 to 15 inches in diameter. When dry, the pink strands resemble red threads. The infected leaf first appears water-soaked, but rapidly dies, becoming light tan. Leaves and often the sheaths are killed.

Grasses susceptible: Bentgrass, bluegrass, fescue and ryegrass.

Conditions favoring disease: Red thread is most serious during periods of prolonged cool, wet weather, especially on turf deficient in nitrogen.

Leaf Spot Disease Melting Out, Going Out, Leaf Blotch

Fungus: Helminthosporium spp

Symptoms: Leaf spot, melting out and going out symptoms include general thinning out of grass in scattered areas, often general browning is evident on affected plant. Circular to elongate purplish, brown to dark brown, or reddish brown spots with white, tan, brown or straw-colored centers on leaf blades, leaf sheaths and stems. Crowns and roots frequently are attached. In hot, windy weather, such plants generally die. Leaf blotch is manifested as tiny purplish to reddish spots on leaf blades and leaf sheaths. Seedlings are very susceptible but developing plants rapidly become resistant. Affected seedlings may die. Small lesions may develop on roots and crowns.

Grasses susceptible: Kentucky bluegrass, ryegrass, bentgrass, and fescue. Improved selections of bluegrass – Marion, Pennstar, Anheuser Dwaft – exhibit a high degree of resistance: Cougar and Delta are moderately resistant: Arboretum and Park are highly susceptible.

Conditions favoring disease: Various species of Helminthosporum are pathogenic over a wide range of temperature conditions (50 to 90 degrees F) under high humidity. Leaf spot generally appears first on grasses in shaded areas and is most severe and damaging on closely clipped turf. Leaf blotch damages young seedlings or adult plants weakened by excess thatch, deficient nitrogen and unfavorable growing conditions.

Snow Mold

There are typically two kinds of snow mold:  Gray snow mold and pink snow mold.  This disease is usually noticed first as the snow melts in the spring. It is commonly found in those turf areas of greatest snow accumulation, such as along driveways or over the brink of a hill where snow drifts tend to accumulate. The most notable symptoms are white crusted areas of grass in which blades are dead, bleached, and matted together. These bleached areas can range from several inches to several feet across. Snow mold has pinhead-sized fungus bodies called sclerotia. These light to dark brown sclerotia are embedded in the leaves and crowns of the infected grass plants.

Recovery can be jump started by raking the matted turfgrass, which facilitates air movement within the turf canopy.

To prevent Snow Mold next year, you need to think about it this year.  Late this fall, mow your grass as low as you dare cut it, the lower the better.   We have a preventative fungicide that can be applied late in the fall before the first snowfall.   Upgrading your fertilizer program to our all organic Nature Safe® fertilizer will also introduce soil microbes that break down the spores of the disease that cause snow mold.

Necrotic Ring Spot

Symptoms
In the early stages, symptoms of NRS often appear as small, scattered, circular, light green to straw-colored patches. As the symptoms progress, the patches become sunken or crater-like and appear as rings or arcs of dead turf. These arcs range in diameter from a few inches to 3 feet or more. Often tufts of apparently healthy grass remain in the center of this  circular area, producing  a “frog eye” pattern. Symptoms may increase in severity at particular sites and then decrease.

About the Disease
The pathogen responsible for NRS survives year to year as mycelia (fungal threads) in dead plant debris, in the thatch layer, and in infected plant parts. NRS most commonly occurs when wet weather is followed by hot, dry periods. Symptoms of the disease on Kentucky bluegrass appear under cool, moist conditions, so it is common to see NRS from mid spring through late fall. The fungus is most active when temperatures are between 50 and 70 degrees F.

Environmental stresses, such as heat and lack of moisture, may weaken the host and make it more susceptible to the disease. Turf grass may be more susceptible to infection when stressed for several years in a row. NR is particularly evident two to three years after sod lawns are established.

The most common problem leading to NRS is laying sod on top of hard, compacted clay soil. The hard soil inhibits root development, enhances thatch buildup, and is water resistant. This leaves the grass drought stressed even though it is watered frequently. Proper site preparation before sodding a lawn may seem expensive at the time but results in a healthier, more pleasing lawn with overall lower maintenance costs.

Control

As with most turf diseases, NRS is principally a disease of stressed turf.   Dense turf with heavy thatch tends to be more prone to infection.  Aerate the lawn twice a year to help reduce thatch buildup and improve soil condition. Mow grass as necessary to maintain a height of 2 1/2 to 3 inches. Make sure mower blades are sharp. Never remove more than one-third of the grass blade at a time.  Water every day with 0.15 inches of water. Avoid watering after 5:00 PM and before 4:00 AM.  During prolonged droughts, when measurable rain does not occur during a two week period, the irrigation should be raised to 0.20 inches per day.  This allows the infected plants with a depleted root system to survive the heat stress of the day.  Use organic fertilizer to increase soil microbial activity.

Rust

Rust is a disease of slow growing turf.  Rust is most noticeable on lawns that are newly planted and malnourished, both excellent conditions favoring the development of this turf problem. The good news is that rust is seldom a serious problem and will rarely completely kill a turf.  Mostly it is just aesthetically unpleasing.  From a distance, rust-infected turf has a yellow green cast.  Close inspection of the rusted leaves reveals numerous yellow-orange pustules on the blades of grass.  Walking through grass that has been significantly infected will result in a rust color orange on one’s shoes or lawn mower.

Maintaining a healthy lawn is the most effective and efficient method of control.  Fertilize the turf with a high dose of nitrogen and avoid watering in the evening.  The grass will eventually outgrow the disease.