In the past weeks quite a few lawns in the area have experienced blades of grass that have turned white. Areas most affected are those in shaded areas, including underneath trees where leaves had fallen.
It doesn’t wash off in the rain. But if you take your finger and rub it down the blade of grass it will probably come off. The most likely culprit is powdery mildew. Gently sweeping the grass with a broom or brush may help but take care not to actually damage the grass itself.
As with any infected lawn area whether a problem is caused by a fungus or mold avoid walking over it and clean your yard tools after they touch any infected area. One more note: never walk on frosted grass which can cause damage to a lawn.
All turfgrass species, but particularly Kentucky bluegrasses and some perennial ryegrasses are most susceptible to powdery mildew. 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.
Cool temperatures about 65°F, high humidity, and poor air circulation favor the development of powdery mildew. The disease is most severe in shady areas. The warmer than normal fall temperatures may have led to an increase in the powdery mildew being present.
Some thoughts are that when spring arrives and the grass begins to grow the white blades of grass will disappear. Others believe that chemical control is needed for everything. But remember there are usually always better options than using harsh chemicals on our lawns. Extreme caution must be used when applying chemical fungicides. Many of these fungicides could be harmful to pets and small children if they accidentally ingest them shortly after application.
One product you could try though is Neem oil used by many gardeners and is claimed to work on powdery mildew. Neem oil is a naturally occurring pesticide found in seeds from the Neem tree. It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products including toothpaste, cosmetics, soaps, and pet shampoos. Neem oil is a mixture of components. Azadirachtin is the most active component for repelling and killing pests and can be extracted from neem oil.
Better options for affected areas are to reduce shade and improve soil aeration. If possible increase sun exposure and increase air movement. Decrease moisture in these section and mow that area a little shorter and more often so it can dry out. Once spring growth kicks into high gear, affected grass will grow out of powdery mildew.
Also, aerate your lawn every year or two. By loosening the soil, you temporarily improve air circulation and drainage, reducing the likelihood of fungi attacks. Periodically perform soil tests to detect nutrient deficiencies that have the potential to invite disease. If you can identify a deficiency before it weakens your grass, you may be able to prevent fungi from developing.
Choose a type of grass that is well suited for your climate and soil. Native grasses have stronger defenses against native fungal spores. Do not use Kentucky bluegrasses in shaded areas.
Instead of allowing the leaves to pile up, remove them completely or use your lawnmower to mulch them into the grass. Powdery mildew most often attacks grass grown in conditions that are too moist and shady,
One other mention is snowmold. 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. 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.