My potted snapdragons started to produce new foliage after they bloomed last month, and aphids moved in to feed. There may already have been aphids on these plants, or perhaps aphid eggs hatched after the plant was moved to a warm environment. They also could have come from another plant in the building as adult aphids can fly. Once they are on a suitable plant, adult female aphids can produce several nymphs each day without needing to find a mate, which is why the population can seem to explode.
Rain will also wash off the honeydew that aphids leave on plants. Honeydew is a sticky, sweet liquid that contains excess sugar (from the plant’s sap) that the aphids can’t use and thus excrete. Honeydew can support sooty mold and it attracts insects such as ants and wasps that feed on the sweet liquid (more about that in a future post). Neither the mold nor the insects are really a problem, but the sticky honeydew is a mess by itself.
The aphids don’t seem to have spread (yet) to the dwarf pomegranate trees, sweet william, or prickly pear cactus that are also growing in my office. I thought about just sacrificing the snapdragon plants and putting the pot outside to freeze the aphids, but first I’m going to try to reduce their numbers. I plan to write more about that in a future post as well.