Currently using a fish oil emulsion, which is somewhat effective, but I continually spray every two/three weeks to keep this under control. I'm in Sarasota, FL.
Need Help With Fungus on Sago Palms
Certified GKH Gardening Expert
Try neem oil. I love neem oil in my garden. It works well as a fungicide and an insecticide and it is organic and safe for people, pets and beneficial insects. It should also be more lasting as it works from within the plant and will not be washed away by rain and weather. This article explains more: