I have a 2 foot tall hibiscus on my balcony and the underside of the leaves and the buds have pale yellow and black spots on them. It doesn’t look like they are bugs or aphids as there is no movement and they squish easily. Picture attached. Please advise, thank you.
Close inspection of your photograph reveals that your hibiscus is indeed infested with aphids. These small insects come in many colours and attack a very wide variety of plants. Reproduction and consequently, infestation, takes place rapidly. Aphids suck plant sap, which causes distorted leaves, buds and flowers and excrete a sticky substance called honeydew, allowing a sooty mold to grow. This mold is unsightly and blocks light from the leaves. Normally, aphids cause damage but do not kill a plant. Remove and squish any you find. As well, move the affected plant away from others for several days. If you purchase new plants, keep them away from your other, established plants until you’re certain they are not infested.
The easiest method of controlling aphids is simply to dislodge them with a forceful stream of water from a hose. This can be repeated a couple of times a week. If the spray is not enough, wash each infested plant thoroughly in soapy water [about 2tsp (10 mL) of mild detergent per gallon (4.5 L) of water — by this, I mean the soap that you use to hand-wash dishes, NOT dishwasher detergent] – spray this onto the plant, making sure you coat all surfaces. Rinse with fresh water after around 10 minutes. You may need to repeat this after a few days.
Although many cosmetic pesticides are now banned in Ontario, insecticidal soaps available at your local garden center are still available. Always read the label carefully, and use only products whose labels specify they are to control aphids.
This website has some good background information on aphids
Good Luck with your hibiscus