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Gardenias covered with black film

Gardening Reference » Gardening in 2006
by Dixie1961 on March 25, 2006 11:54 AM
I have several large gardenia plants that have tiny little scales on the back side of the leaves, and a black coating on the top of the leaves. I have tried several insecticides, plant shampoo, and a tonic using cayenne pepper. None of these has helped. I live in Georgia.
by Longy on March 26, 2006 12:48 AM
Scale insect is the problem, the black sooty mould is a symptom. You can spray the scale, on a cool day, with a whiteoil mixture and some insecticidal soap. It's a contact thing so you'll need to drench the underside of the leaves. Spray 3 times 7 days apart and give your gardenias a feed of low nitrogen fertiliser. Something with a little extra potash would be good. This will help the leaves to toughen up a bit and make them less palatable to the scale and other sucking insects..

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The secret is the soil.
by Buglady on March 26, 2006 01:19 PM
Are the plants growing in pots or in the ground? if in pots indoor or outdoor? This will make a difference on fertilization. Gardenias are typically heavy iron feeds but don't over feed, sometimes that can attract pest insects.

Also with scale insects, one you treat them and get contact with them, they can still look alive for several weeks. Same thing with sooty mold, it can take weeks for it to wash off even after the scale is dead.

So if you used horticulture oil and got good coverage you may have solved the problem. Do not use more them a 1% oil mix.

PS its some kind of soft scale.

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The Buglady
Suzanne Wainwright-Evans,
Educating the world... one bug at a time

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