Lawn Diseases - Dollar Spot
Dollar spot is another common fungal disease of turfgrass. All of the commonly used turfgrasses including bluegrass, tall fescue, fine fescue, perennial rye and zoysia grass are susceptible to Dollar spot although some cultivars of each grass species have greater resistance to the disease.
Dollar spot is most severe on lawns that do not receive adequate fertilization. Warm, damp nights that result in high humidity around the grass canopy for long periods of time are optimal for the growth of Dollar spot fungal spores. Injury is usually most severe when daytime temperatures are 70 to 80 degrees and the soil in dry. Excessive thatch and low soil nitrogen and potassium levels also promote Dollar spot development.
Dollar spot gets its common name from the size of the affected spots of grass in the lawn. Usually the spots will be about the size of a silver dollar. Large leaf spots or lesions develop across the entire width of the leaf blade and are light tan or whitish with a medium reddish-brown border. On coarser bladed grasses like tall fescue, the lesions may develop along the edges of the leaf blade and could be confused with Brown patch. Brown patch, however, has a much darker brown or purplish-black margin around the leaf spot. Dollar spot lesions are also typically 'pinched in' at the middle of the lesions giving an hourglass effect. Infected leaf blades eventually die leading to quarter or silver dollar sized dead spots in the lawn.