They suck the sap and often cause new leaves and flower buds at the tips to grow in a distorted way. Heavy infestations can set a plant back a few weeks, but they are easy to knock-off with the spray from a hose.
Some adults can fly, so they'll be back. As is often mentioned, hanging a bird feeder near the affected shrubs can help (they eat aphids while waiting a turn at the feeder) until the ladybirds and other natural predators find and deal with them. Until then, just keep an eye out and squish or knock off with a spray.
A trowel in the hand is worth a thousand lost under a bush.
Posts