Answer: Whiteflies can be a major problem with indoor plants. Horticultural oil won't affect the adult whiteflies, although it might smother any eggs on the stems or undersides of the leaves. Instead of spraying with oil, why not try to trap the adult whiteflies? Use a square of bright yellow cardboard or stiff paper, smear it with petroleum jelly and mount it in or near the foliage of your Hibiscus. The yellow color will attract the whiteflies and they will get stuck on the surface of the trap when they land on it. Remove and replace the trap when it's no longer effective. You can also discourage whiteflies by spraying them with Insecticidal Soap. The spray has some residual effect, but will work best if you can directly spray the insects.
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