Dollar spot symptoms occur anytime from early to late summer. The disease usually reaches peak activity when air temperatures are in the 80 F range and under high humidity. Symptoms also may appear in the fall. The most severe cases of dollar spot occur on turf receiving closely-spaced summer irrigation. The disease may also occur on nonirrigated turf when humidity is high from prolonged muggy summer weather.
Dollar spot is more severe under nitrogen deficiency or when grass grows slowly.
Dollar spot lesions on Kentucky bluegrass leaves. Mycelium may be carried by the wind, water, or on turf equipment and shoes. This fungus does not produce spores. Sclerotinia homoeocarpa is thought to survive as thick-walled crusts of mycelium called pseudosclerotia in dormant infected plant tissues. On lawns, fertilizer that releases nitrogen slowly over an extended period is more advantageous than a quick-release product at this time of year.