While there are several toxic chemical pesticides available that kill aphids, there are natural, organic methods available. Aphids feed on the sap inside your hibiscus, which can lead to weak plants, cause buds not to open, new limbs can grow deformed. Viruses can be attracted to the open wound and the sticky residue aphids leave behind.
Purchase predatory lady beetles, also called lady bugs, from a local greenhouse or nursery and release the beetles directly onto the hibiscus. The lady beetles feed on the aphids for a period of a few days, but will eventually disperse around your garden area.
Make a homemade aphid trap by mixing a cup each of sugar, water and vinegar in an empty gallon-sized water jug. Chop a banana peel into small 1-inch pieces and add it to the mixture. Hang the jug with the lid off at, on or near your hibiscus for a week. Discard the mixture and make a new batch each week to continue to attract aphids.
Create an aphid-killing spray that is safe for your hibiscus by mixing a gallon of water with 3 tbsp. of dish soap. Spray the solution onto your plant between morning and noon when the plant is dry from nighttime dew, but it is not yet in the heat of the day. Reapply the spray every four to five days when aphids are present.