Relationship Between Weather Factors and Dollar Spot of Creeping Bentgrass

In 1981 and 1982 epidemics of dollar spot of creeping bentgrass, caused by Sclerotinia homoeocarpa, proceeded in a series of steps. Each step began at a point where a decline in the epidemic rate was followed by an increase in the epidemic rate and continued until a new step began. A step in the epidemic occurred after two consecutive wet days if the average temperature for the period was at or above 22 °C or after three or more consecutive wet days if the average temperature for the period was 15 °C or greater. These weather conditions were referred to as "infection periods." In 1982, an application of Tersan 1991 (benomyl) 1 and 2 days after two infection periods provided an acceptable level of disease control as effective as that obtained from a regular preventive schedule of seven sprays.