What Are Black Powdery Spots on Grass?
- Necrotic ring spot is a common lawn disease that can manifest itself as visible black mold patches on your lawn grass. Parallel symptoms include large patches of grass (6 to 24 inches) of discolored grass with straw- and red-colored blades near the center. Necrotic ring spot can be difficult to manage in lawns. Keep thatch layers no more than 1/2 inch thick and adjust fertilization and watering schedules to recommended levels for your species of grass. Extreme cases can be treated with a fungicide approved to control necrotic ring spot.
- Another possible diagnosis is infection by slime molds. In addition to patches of black mold, you may also notice gray, pink, yellow or orange patches occurring intermittently across your lawn. Slime molds are typically nothing more than a cosmetic concern for lawns; they do not lead to turf degradation or any other serious lawn diseases. Simply rake or till away the diseased patches of your lawn and replant new grass where necessary.
- Stripe smut also can create patches of black powdery mold on your lawn grass. Stripe smut is caused by the fungus Ustilago striiformis and is also common in cooler climates. Symptoms begin as elongated streaks that are yellow-green; if the disease if left untreated, the streaks turn gray and finally black. Stripe smut can be easily controlled with a single application of nitrogen-rich fertilizer and deep watering early in the day. As with other diseases, extreme infections can be treated with a fungicide.
- Always approach the use of chemical fungicides with extreme caution. Some fungi and other micro-organisms play a beneficial role in your garden or lawn, and these micro-organisms can sometimes be adversely affected by the use of chemical fungicides. If necessity warrants the use of a fungicide, always read and understand the manufacturer's application instructions and understand all potential health and environmental effects of that fungicide before using it.
