Expert: C.L. Fornari - 5/20/2008

Question
i submitted this question before but did not receive a response. we have some small (about 1/16") diameter hard shell casings all over the leaves of our gardemia bush. The plant looks healthy & has many blossoms on it. we have sprayed it against black spot & white flies. any ideas?

Answer
Joe,
If you submitted it before it must not have come through because neither I nor AllExperts has it on record - they are very good about letting me know if anything has slipped through the cracks!
 
There is no disease that I'm aware of that causes what you describe. If a gardenia has a sucking insect such as whitefly it can get a charcoal colored coating that is called "sooty mold" which is what grows on the fluids that the insects secrete. The problem will be corrected when the insects are gone.

Caterpillar poop might look as you describe - or perhaps what you see is something falling from neighboring trees?  In any case, if this were my plant I would brush anything you see off the leaves and watch the plant on a daily basis. Look at neighboring plants and see if they show the same thing, and if so, look to see if there are taller plants that might either be shedding something or be harboring caterpillars or other insects.  If the gardenia is growing well and the buds and blooms are developing well then you can assume that the casings you report are not a problem.

all the best,
C.L.