Posted by mike g on June 08, 2003 at 23:55:43:
In Reply to: Gardenias: Sooty black mold & shiny black bugs posted by Dolly Samson on May 25, 2003 at 21:13:43:
: We have two gardenia plants. One is fine. The other is covered with sooty black mold. For the past year, I've washed the leaves with dish soap, but the mold keeps reappearing.
: I see no sign of white flies on the gardenia. However, there are a number of green-black iridescent bugs, shaped like ladybugs. I've also sprayed it with Volck.
: Any suggestions? I'm tired of washing those leaves!
: Dolly Samson
The plant has sooty mold. This is caused by several fungi that grow on the sugary material left on plants by aphids, mealybugs, scales, whiteflies, etc, that suck sap from the plant. Sooty molds are ugly but are harmless because they dont attack the leaf directly, but only the substance (honeydew) left behind by the bugs.
The green-black ladybug-shaped irridescent bugs may be aphids or leafhoppers. You'd want to find out which is which and proceed with action. I'd spray the tree with a bacterial insecticide called baccillus thuringiensis (Bt.) and stop washing the plant with dish soap.