Red Thread Lawn Fungus and How to Control It
I’ve gotten several questions regarding lawn diseases over the last few weeks, so here is some info on a common one that appears quite often. The thing you need to remember with this lawn tip is that most turf fungus is NOT a major concern and will go away on it’s own with proper fertilization, watering and mowing on your part.
Red Thread lawn fungus appears in turf as small pinkish-red spots or patches, usually in later May and June when temps are high, and humidity is higher. Infected areas eventually turn light tan, and the leaf tips or margins may be covered with fine pink to red threads, giving the turf an overall pink coloration.
Red Thread, also known as “Pink Patch,”occurs in the cooler and more humid areas of the Pacific Northwest, Northeast, and Midwest. It is most severe on slow growing, nitrogen- deficient turfgrass during damp weather. We have had these exact conditions here in Chicago and Northwest Indiana these past few weeks of early June. (lots of rain, heat and humidity)
Susceptible turfgrasses include bluegrasses, bentgrass, fescues, bermudagrass, and perennial ryegrass. The fungus actually overwinters on the leaves and in the debris of previously infected plants. The leaves and leaf sheaths appear to be the only grass parts that become diseased.
Symptoms begin on the leaf blades as small, watersoaked spots that rapidly enlarge to cover a large portion of the leaf or the entire leaf sheath. As these spots enlarge, the tissue dries out resulting in gradual fading to a tan color that may encompass the entire leaf blade.
During extreme humidity, the leaves may be covered with a pink fungal growth, which along with the grass tissue, forms thread-like material upon drying out. The coral-pink colored thread-like material extends from the ends of leaf blades and may also be present on the surface of leaves.
Areas of diseases grass range from two inches to several feet in diameter. The outside edge of infected areas have an uneven or “ragged” appearance.
Conditions That Encourage Red Thread Disease
Development of the disease is favored by air temperatures in the 70 to 80 degree range, coupled with prolonged wet conditions (rains, heavy dew, and fog). Increased severity occurs on turfgrass growing in soil that lacks nutrients, especially nitrogen.
Control
My personal approach to controlling or eliminating Red Thread is 3-fold.
- Keep lawn properly fertilized with slow-release nitrogen: I always recommend using Milorganite Organic Fertilizer. You should apply Milorganite in April and again in early June.
- Secondly, a granular fungicide will help the situation if applied BEFORE symptoms appear. I apply 2 applications of granular fungicide per year; once in mid-May and again in later June.
- Mow your lawn the proper way and catch clippings when disease is present. If you do water, water deeply and consistently twice per week. NEVER WATER AT NIGHT!
Another way to help fight Red Thread is by keeping your lawn’s thatch layer in proper balance. Heavy thatch layers are conducive to disease development. If thatch is thick or the soil is compacted, aerate for a healthier lawn. You can aerate your lawn at any time of the year as long as you can pull plugs.
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