The Q&A Archives: Gardenias and horticultural oils

Question: I noticed the leaves on my gardenias were turning black and looked terrible, but the plants still bloomed in June. I read I should apply horticultural oil to get rid of the scales. But it is July here and too hot for the oil. Any other way I can help my gardenias?

Answer: Debora,

Scale treatments are usually applied in late winter. Oil can be damaging in the heat of summer, especially dormant oils although horticultural or "summer" oils are safer. That said the black leaves could be from some other insect such as whiteflies, aphids or mealybugs. You may want to take a sample to your County Extension Office and see if they can identify the problem and if necessary prescribe an appropriate remedy.

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