Sooty Gardenias

April 18, 2008 | By | Comments (6)

08 04 gardenias 2 Sooty Gardenias

Q: I have 2 gardenias that are covered in black soot. I have seen tiny little white bugs flying around them (I assume these are white flies?) I would like to clear up the white fly/soot problem, as well as relocate these two plants. Each is about 4ft. tall and 5ft wide. I live in Lexington, SC, and our soil is quite sandy. Any advice you can offer would be appreciated. And I just loved your column in Southern Living and am so glad I found your blog! – Candy Hayes
Lexington, SC

A: Dear Candy,
Aren’t you sweet? (OK, I’m sorry about the bad pun. I won’t do that again.) White flies are the main culprit here. They suck juices from the gardenia foliage and then secrete a sticky honeydew upon which the sooty mold grows. Get rid of the white flies and the sooty mold goes too. Ah, but it isn’t that easy (naturally). White flies are very difficult to control and eradicate, because they multiply faster than Dustin Hoffman in “Rain Man.” My advice is to treat your gardenias with a systemic insecticide that the leaves will absorb and pass on to the white flies. Spray the plants according to label directions with a chemical called acephate, which you’ll find in several pest products, such as Orthene. You’ll have to spray several times at two-week intervals. Be prepared — the stuff smells bad. But so do husbands early in the morning.

You might also consider applying a systemic insecticide that’s absorbed through the roots, such as disulfoton. It’s often included in insecticide-fertilizer combo products like Bayer Rose & Flower Care. Again, follow label directions. –Grumpy


  1. Grumpy Gardener (His Magnificence)

    The easiest test for white flies is to brush a leaf. If white things fly, they’re white flies. If they don’t, you may have mealybugs. You can treat for them the same way.

    August 3, 2011 at 4:46 pm
  2. Bert

    I have white sticky substance on my bonzi gardenia. It had large white flowers in the spring and has 6-10 large buds on it now. Recently it has dead leaves on one side and I noticed the white sticky stuff this morning. Is this still white flies?

    August 1, 2011 at 11:25 am
  3. Grumpy Gardener (His Benevolence)

    White fly eggs might still be around and it doesn’t take many of them hatching to create a big problem. I would treat your gardenias according to label directions with Bayer Advanced 12-Month Tree & Shrub Care. Here’s a link:

    April 21, 2011 at 2:55 pm
  4. Jessica

    I have three gardenias that have the sooty black mold on them. I haven’t seen white flies on them since last spring/summer, but the mold remains. Should I still treat them the same way as you advised above?

    April 19, 2011 at 9:01 am
  5. Grumpy Gardener (His Benevolence)

    Hey, if it works, keep doing it.

    April 14, 2011 at 9:20 am
  6. Brandy

    My grandmother told me to use warm soapy water for white flies. I’ve done this before and it seems to work What are your thoughts?

    April 12, 2011 at 1:09 pm

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