Turn off the sprinklers when you receive ample rain during the fall, winter and spring months.
When it is cool and moist, fungus will form in St. Augustine and Zoysia grasses. We recommend spraying Liquid Vitae organic fertilizer to reduce damage, but there is really no way to fight it except to reduce the moisture. It is recommended to water only once per week in the winter. However, in South Florida, there have been some events where it gets hot and dry all of a sudden. Best to keep an eye on the system to reduce fungus issues. My rule is this: if it rains, turn off the system (primarily mechanical timers) for about a week or so. This allows the landscape to dry out before you begin to irrigate again.
Two plant pathogenic fungi in turf grasses are Rhizonctonia solani and Sclerotium rolfsii.