Succulents are low-maintenance, drought-resistant plants that have adapted to life in arid climates. To survive lengthy periods of dry weather, succulents store water in their leaves. As a result, the plants bear plump, fleshy foliage that expands or contracts in response to the amount of moisture in the environment. While succulents tend to be pest-free, the occasional insect problem can arise, particularly during hot weather when pests are drawn to the succulents' soft tissues and their ample supply of fluids.
Aphids are tiny, soft-bodied black, green, yellow or pink insects that cluster on the undersides of shoots, leaves, flowers and stems. This not only hides them from predators, it keeps them from being washed away by rain or irrigation. Adult aphids use their needle-like mouth parts to pierce plant tissues and remove vital fluids, which leads to shriveled foliage and stunted plant growth. In addition, aphids coat plants in a sticky residue that can lead to the development of a fungal disease known as sooty mold.
Many aphid infestations can be resolved by spraying the affected foliage with a strong stream of water each morning until the insects are no longer apparent. Desert-dwelling succulents do not respond well to daily doses of water, however. Treat aphid infested succulents with a soap-and-water solution made from 2 cups water, 1 tsp. liquid dish washing soap and 1 tsp. vegetable oil. Pour the ingredients into a plastic spray bottle, shake gently, then lightly mist the affected foliage. Coat both sides of the leaves; the insects must come into contact with the solution for the treatment to be fully effective. Wait three to four hours, then wipe the leaves with a damp rag to remove the soapy residue. Reapply every three days until the situation is resolved.
How it Works
Aphids and other insects breathe through small openings known as spiracles. The combination of soap and oil clogs the spiracles, making it impossible for them to draw air, causing them to suffocate. Additionally, detergents found in most liquid dish washing soaps strip the protective coatings from the aphid's body, which leads to death through dehydration.
Rinse the soapy film off of the leaves after the aphids have been sprayed. If the solution remains on the foliage, it can damage the plant. The same combination of soap and oil that blocks the aphid's spiracles can clog the pores on the surface of the foliage, interfering with processes such as transpiration and foliar feeding.