Always test soap or detergent on a small area of the plant. Horticultural oils are refined mineral, vegetable or paraffin oils that act as a physical control on aphids. These differ from dormant oils in that they can be used on growing plant tissue. It coats and smothers the insect while interfering with the aphids respiration. These oils will also help to remove the sooty mold that grows on the honeydew.
Complete coverage is essential with oils and soaps.
Some plants may be sensitive to oils especially during high temperatures or high humidity. Aphid problems originating from eggs that overwinter on the plant also can be controlled with dormant oils. These are less refined oils or petroleum oils than the year round pesticidal oils, and can only be used when the plants are dormant in early spring or winter. Where high water pressure is available, infested plants may be hosed with water to reduce aphid numbers. This also removes recently deposited honeydew.