Lawn Fungus in Late Winter

by Ashley Mackenzie

    Lawn fungus favors damp conditions and warm temperatures, which makes late winter in Mediterranean climates a favorite time for it to develop. Fungal diseases usually show up as circular patches of dead grass on your lawn, but the centers of these patches often heal, leaving dead rings of grass with healthy green centers. Occasionally, fungus can lead to related problems, such as the disease powdery mildew. Fortunately, you can prevent lawn fungus and eliminate it with special care.

    Rhizoctonia Large Patch

    Rhizoctonia large patch affects bermudagrasses, St. Augustine grass, kikuyugrass and zoysiagrass when temperatures are cool and conditions are wet. This makes late winter a susceptible time, when weather is still damp and temperatures are between 60 and 70 degrees Fahrenheit. Symptoms include circular brown patches and wilting of the grass; the infected patches grow from small spots to rings of brown grass several feet across as the disease spreads.

    Brown Patch

    Sometimes spring temperatures hit early, causing fungus to develop in the warm, damp weather. If temperatures are more than 75 degrees Fahrenheit by day and 60 degrees Fahrenheit by night, with rain or humidity leaving foliage damp, brown patch -- a type of Rhizoctonia fungus -- can become a problem. This fungal disease affects both warm- and cool-season grasses. Circular patches of thinning, light brown grass are the most obvious symptoms, but you should inspect grass carefully to diagnose the disease. The grass blades often show signs of disease, such as shriveling or brown spots with dark rings.

    Red Thread and Pink Patch

    Red thread (Laetisaria fuciformis) and pink patch (Limonomyces roseipellis) are fungal diseases that favor the same conditions, so they often go hand-in-hand. Late winter weather that's moist, with temperatures between 65 and 70 degrees Fahrenheit, support the development of these fungi. You can spot them by looking at your lawn from a distance; affected grass has a pinkish or reddish hue. Up close, this hue is a result of the fungus spores, which look like fluffy pink growths or miniscule red threads sprouting from the tips of leaves.

    Preventing Late Winter Fungus

    You can help prevent fungus from overtaking your lawn in late winter by watering in the morning; this gives your lawn a chance to dry before nightfall, when fungus develops. You should also water deeply but infrequently to prevent excessively damp conditions. If your winter is rainy, you may not need to water your lawn at all. Without warm, sunny conditions, your lawn in late winter remains damp longer, meaning less frequent watering is necessary.

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