Q: My hibiscus shrubs bloom from mid-summer thru fall. The buds and leaves have all turned black and they have white insects all over them. 

A: Hibiscus whitefly is a common pest of outdoor hibiscus plants. The small white flies gather on the back of leaves and suck sap. The sap that cannot be digested is excreted and it falls on nearby buds and leaves. A sooty black mold grows on the sap (honeydew), causing the whole plant to be unattractive. The first way to control whiteflies is to spray the plant with a strong stream of water every three days. This will wash away many whiteflies and their eggs and will also get rid of the sooty mold. A systemic insecticide can be used as a last resort but I don’t like doing this because of the danger to pollinating insects.