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Diseases

Steps to Prevent Disease

Diseases can occur from spring until fall, but are most common during the summer. They can occur for a number of reasons, but usually moisture and temperature are the main factors. Most diseases form under cool, moist conditions, but damage does not appear until high humidity and temperatures begin. Grass will generally turn yellow or brown in the sunny areas of your lawn, and damage can become severe if curative steps are not taken. Below is a list of important things to remember that will help your lawn recover and prevent disease in the future.

Water in the early morning (4am-8am).

Dew naturally forms on your lawn overnight, generally drying out by mid morning. Watering during the late morning or evening will extend the period of time the lawn is wet, allowing diseases the opportunity to form and spread.

Water less frequently, but longer each time.

Watering everyday also promotes disease activity. Watering less frequently, but longer each time will help dry out the lawn between waterings, but still provide the 1.5-2.0″ of water per week that is needed.

Bag your clippings.

Bagging your clippings will remove the diseased grass blades from your lawn. Mulching after a disease has formed can worsen and lengthen the disease activity.

Mow tall.

Mowing tall will reduce heat and drought stress on your lawn and help it recover more quickly.

Sharpen your mower blade.

This will provide a cleaner cut making your lawn less susceptible to disease.

Plant disease resistant seed.

This will help prevent disease from re-occurring in the same areas of your lawn.

Aerate your lawn in the spring or fall.

Aeration will reduce thatch and strengthen the root system making your lawn more disease resistant.

Apply a preventative or curative fungicide.

This will greatly reduce the chance for disease and its severity. It will also help the lawn recover more quickly and prevent the disease from spreading.

Common Lawn Diseases

DOLLAR SPOT– Dollar spot damage first appears as small, round, bleached spots ranging in size from a quarter to a silver dollar. In severe cases, the spots will merge into larger patches. Individual grass blades develop a bleached lesion that spans across the grass blade. Dollar spot can occur from late spring through fall, but is usually most active between 70-80 degrees. An application of fertilizer high in nitrogen and potassium will generally help the lawn recover. A fungicide application will usually control the disease.

LEAF SPOT– Leaf spot damage first appears as fading out of the turf. In severe cases, rotting of the grass roots and crowns may occur. Small oval, dark spots appear on grass blades causing the lawn to lose color. Leaf spot is most active during the late spring with temperatures between 65-80 degrees and during prolonged periods of cloudy and overcast days. Leaf spot is fairly easy to control and several general curative fungicides will help the lawn recover. 

SUMMER PATCH– Summer patch damage first appears as 6-12″ semi-circle or crescent shaped dead patches in the sunny areas of the lawn. As the disease worsens, the patches often run together forming a “frog-eye” pattern. The dead grass is yellowish brown and matted. Summer patch is most active between 80-90 degrees and usually breaks out during hot weather that follows a wet period. It can be a very damaging disease spreading throughout an entire lawn. Although curative fungicides can help the lawn recover, preventative fungicides are recommended. Applications need to be applied repeatedly beginning in late May.

BROWN PATCH– Brown patch damage first appears as light brown, roughly circular patches that have a sunken look. As the disease worsens, the patches may grow up to 2 feet in diameter, and cover large areas of the lawn. A grayish “smoke ring” may be seen around the edge of the patches. Grass blades will have irregular bleached spots surrounded by dark brown margins. Brown patch is most active during hot, humid weather with temperatures above 85 degrees. Like summer patch, brown patch can be a very damaging disease. Curative fungicides can help the lawn recover.

POWDERY MILDEW– Powdery Mildew appears as white to gray dust on grass blades. It usually occurs in areas with heavy shade and poor air movement. In severe cases, grass plants may wither and die. Powdery mildew is most active during the summer and fall. Increasing light intensity and air movement will help the lawn recover. A general curative fungicide will also help, but is rarely needed.

RUST– Rust appears as orange to reddish brown pustules on grass blades. It is easily noticed on shoes and mowers that have passed through an infected area. In severe cases, the lawn will thin out from the loss of leaves and stems. Rust is most active during the late summer when cooler nights produce heavy dew. Avoid watering during the evening and limit activity in the areas that have rust to keep the disease from spreading. A general curative fungicide will also help the lawn recover.

FAIRY RINGS & MUSHROOMS– Fairy rings appear as dark green circles or semi-circles in the lawn. They vary in size from 1 to 10 feet in diameter. They are caused by the decay of buried stumps and other pieces of wood. Fairy rings often contain clusters of mushrooms and puffballs. Mushrooms grow from decaying organic matter and are most likely to form in areas with high organic debris, such as buried wood. Mushrooms grow best under wet conditions, but die off quickly with warm, dry air and sunshine. Fungicides do not suppress fairy rings or mushrooms, so it is recommended to dig up and remove the soil in the infected area.