Dollar spot fungus is caused by a fungus that causes blight to grass blades, but does not harm roots or crowns. Infections start as small circular areas about the size of a silver dollar, hence the name.
Dollar spot is commonly found on lawns with excessive thatch and low moisture in the soil. It also is found in lawns with low fertility.
This fungus is active from late spring through early fall. High humidity and air temperatures of 65° to 80° F encourage the growth of the dollar spot. Infected areas of turf are straw-colored, matted patches about the size of silver dollars. Dollar spots can infect turf along the tracks made by lawn mowers and lawns mowed higher than two inches. These infected patches are usually larger and more irregular.
Fine, “cobwebby” fungal threads (mycelium) may be evident in infected areas in the morning when dew is present. Individual leaf blades display an hourglass-shaped lesion, or spot, which is straw-colored with a reddish-brown margin.
A fungicide application program may be necessary when dollar spot is prevalent. Good cultural practices can also reduce the potential for a dollar spot to infect your lawn. These include removing excess thatch, maintaining adequate fertility and soil moisture, and seeding or sodding with disease-resistant cultivars. Also, do not mow when the turf is wet. To find out which fungicide may be best for your property, consult your local landscape professional