I owuld say to call your local extension office. My husband and I are in the process of being liscensed as a backyard nrsery and the inspector said parts of our town are infested ith a type of hibiscus scale.. She said they cause yellowing leaves and appear to be a fuzzy crawling ick that is actually a pink scale, it also causes flower buds to fall off. She didnt say what hemicals to use but that they were releasing benificial bugs to deter it where it is found so they may be able to help.

Good Luck
Donna / Jacksonville

you have scale on the woody part spray them with soap and water to kill the scale. The leaves will fall of this time of year because of the cooler temps. You might want to talk to the folks at http://www.hendrychapterahs.com/photo_player_flash11.html they are the hibiscus chapter in your area or get a hold of Curt Sinclair at his Phone: 941-322-2841
Add'l: 863-674-1902