Lawn Diseases - Necrotic Ring Spot

Symptoms of necrotic ring spot appear as circular, ring-shaped, or serpentine patches of dead or dying turf. Affected areas may be a few inches to a foot or more in diameter. These patches may at times coalesce, or they may stand out as individual dead rings. Leaves and stems of affected turf appear yellow or red, then turn a light tan as the disease progresses. Roots and crowns of diseased plants are rotted and recovery of affected areas is slow. Necrotic ring spot seldom occurs in newly planted turf but can occur on turf that has been recently sodded. It may begin during the fourth or fifth year following seeding and can become progressively more severe.
Necrotic ringspot is caused by a soil-borne fungus called Ophiosphaerella korrae. The fungus survives from year to year on dead, colonized bluegrass roots and crowns or on the surface of living roots. The fungus actively colonizes the outside of roots at soil temperatures between 65 and 80 F. These temperatures occur from mid-May through mid-September along the Front Range, but may vary somewhat on the Western Slope and at higher elevations. The fungus eventually penetrates roots and colonizes the root cortex. This either debilitates or kills roots and leads to a decrease in water and nutrient uptake by the plant. Plants with extensively damaged root systems are more prone to injury or death, particularly during periods of high temperature or drought stress. Thus, NRS symptoms often don't show up until July or August even though root colonization begins in May and continues throughout the summer.
Lakeville MA
Mockingbird Hill
Tree and Lawn Care
Since 1987