If you are experiencing excessive growth of dollarweed then try cutting back on watering.
Dollarweed by nature is an aquatic species that thrives in excessive moisture.

Check Irrigation Zones

Check irrigation heads on occasion to make sure that they are providing adequate coverage throughout your lawn without spraying too much into the street or driveway.

Mow St. Augustine Between 2.5"-3" Tall

St. Augustine grass prefers to be mowed between 2.5"-3" tall. Mowing any shorter could expose the roots and cause them to dry out.

Check Mower Height

Never mow more than 1/3 of the grass blade at a time.

Aerate to Promote Growth

Aerating your lawn will help to relieve compaction and promote root growth. Thatch buildup can choke your lawn.