Aphids

Aphids are small, soft-bodied insects, usually green, black or gray, that feed by piercing plant stems and leaves to draw out sap, typically clustering densely on tender new growth, flower buds and the undersides of leaves. They are among the most common pests on balcony container plants, since the plants are often isolated from the natural predators, like ladybugs, that would keep aphid numbers down outdoors in a larger garden.

A heavy aphid infestation can cause curled or yellowing leaves, stunted new growth, and a sticky residue called honeydew that aphids excrete, which can attract ants and encourage a black sooty mold to grow on leaf surfaces. Because aphids reproduce very quickly in warm weather, a small cluster can turn into a serious infestation within a week or two if left unchecked.

Control usually starts with the least aggressive option, a strong spray of water to physically knock aphids off the plant, followed by insecticidal soap or neem oil for persistent populations, applied to the undersides of leaves where aphids cluster. A common mistake is spotting a few aphids and assuming they will go away on their own, when checking new growth every few days and treating early keeps a small problem from becoming a plant-wide infestation.