PEST BULLETIN Fairy Rings & LDS   July 15, 2002 August 20: Symptoms (similar to those in photo #5) from fairy ring fungi have resurfaced after the weather front has gone through, hammered us with rain, and left dryer, cool days behind. Reports of fairy ring and localized dry spot (LDS) have slowly but steadily trickled in over the past few weeks from central Illinois and Chicagoland. Fairy ring type fungi cause a myriad of disease symptoms depending on their type. Local symptoms and damage have included rings of lush green growth (Photo 1), rings of burned out dead grass (Photo 2), puffballs or other mushrooms (Photo 3), LDS (Photo 4), and distinct, thinned out white patches (Photo 5). Fairy Rings Fairy rings are caused by a number of basidiomycete fungi, which may produce mushrooms or may be sterile. All of these fungi primarily colonize the thatch layer and rarely invade more than 0.5 to 1 inch of the underlying soil. These fungi are mostly saprophytic, as they feed on dead grass debris and therefore cause little damage. However, in times of high activity, excess nitrogen (in the form of ammonia) can be released by the decomposition of organic matter and taken up by the plant (Photo 1), and the thatch and underlying soil where the fungi are active commonly become water repellent (hydrophobic). These two factors combine to cause a severe drought condition, and in high temperatures, the succulent plants on the outer edge of the rings (Photo 2) or in patches (Photo 5) simply cook, and thin out or die. Fairy rings are classified into three types based on their appearance and the type and level of damage done to turf. Type A: Mycelium is sparse and abundant, and fruiting bodies may or may not form. The mycelium colonizes grass shoot bases, rhizomes, and stolons in the thatch. There is little or no effect on the growth of grass. Type B: The fungi stimulate turf growth and/or cause discoloration of the grass. The thatch is decomposed, but the grass plants are not severely injured and later recover. Type C: These fungi produce severe injury to the grass; earlier and  adjacent turfgrass growth amy or may not be stimulated. LDS Also associated with a number of unidentified basidiomycete fungi, LDS is common on sand topdressed bentgrass greens and on fairways. LDS commonly appears in new turf areas within 2 to 3 years after seeding or sprigging, but tends to decline over time. The patches are round to irregular and can range from several inches to several feet in diameter (Photo 4). The soil within patches remains very dry despite frequent rains or irrigation because the soil becomes impervious to water filtration. The hydrophobicity of the soil is thought to be caused by older fungal mycelium breaking down and releasing orgainic substances that form a coating over and around individual coarse sand particles. The sand particles in the upper layer of soil become bound together, preventing water entry.   Photo 1 Photo 2 Photo 3 Photo 4 Photo 5 (click on an image to enlarge it.) Management Severity of fairy ring and LDS symptoms can mostly be reduced by mechanically removing excess thatch, core aerification (spot aerifying trouble areas), water-inject cultivation, and use of a turf wetting agent, at one or two week intervals during dry periods. Daily syringing of LDS is necessary to keep turf alive during hot periods, and some managers use a water injection fork on bad areas. Fungicides with activity against basidiomycetes (ex. flutolanil) have also been shown to reduce the severity of LDS. Photo #1.   Fairy rings are normally first seen as a ring of lush green grass caused by an increased amount of nitrogen (ammonia) made available to the grass roots by the fungus as it breaks down organic matter in the thatch or soil. Photo #2. During hot periods, drought and heat stress can be induced by fairy ring fungi either by overnitrification or water repellancy. Photo #3.   Mushrooms, or puffballs, like this Lycoperdon sp., are oftentimes associated with fairy rings, and can cause problems with ball roll on putting greens. Photo #4. Fairy ring fungi in the thatch layer may also cause LDS symptoms by coating the soil particles and making them hydrophobic. Photo#5. These fairy ring type fungi may also be causing patches like this to appear on sand-based greens.