They must have time to harden off before the threat of frost. Read the label carefully. Aphids on crape myrtle and gardenia. Sooty mold on citrus, gardenia, crape myrtle, and other ornamentals. Caused by aphids, whiteflies, and mealy bugs, it may be controlled with an insecticide or insecticidal soap spray.
Spider mites on ornamentals.
Look for their presence on the underside of leaves. A cold blast of water from the garden hose will knock most of them off. If you still aren't sure, rub your hand over the specks and look for tiny streaks.