Dollar spot is caused by a fungal pathogen (Sclerotinia homoeocarpa) that attacks grass leaf tissues but does not affect turfgrass roots or crowns. The disease is common in residential lawn turf and can impact the lawn’s aesthetic quality and contribute to an overall decline in grass health. Dollar spot is one of the most readily identifiable diseases with it’s characteristic small round, tan-colored spots. The spots often occur in clusters and can cause considerable damage to the lawn surfaces if not appropriately managed.
The dollar spot fungus begins to grow and infect susceptible grasses in the spring when night temperatures exceed 50°F, even though symptoms of the disease may not appear until later in the spring or early summer. In addition, the pathogen requires extended periods of leaf wetness, 10 to 12 continuous hours. Heavy dews that often form during cool nights in the late spring or early summer are most conducive to the disease. Extended periods of wet, overcast weather can also lead to severe dollar spot epidemics on susceptible grasses. Dollar spot remains active throughout the summer in many areas, but disease activity typically slows when high temperatures consistently exceed 90°F.
Dollar spot is most prevalent when nitrogen levels drop. A healthy dose of fertilizer can knock out the disease and improve the appearance of the lawn, but sometimes an anti-fungal treatment is required to kill the disease. If you see these circular spots in your lawn, give us a call to discuss the options.