The insects survive by sucking the sap and juices from the soft, new growth, causing injury to plants. These injuries damage the plant's ability to properly process food and causes the plant to lose vigor, wilt, distort or show spots. Aphids can also transmit viral diseases from unhealthy plants to healthy plants.
Aphids often live in large clusters or colonies and are found in the company of ants. Aphids and ants have a symbiotic relationship. Aphids excrete honeydew after digesting the plant substances. (Honeydew is a sticky, sweet substance that is produced by the aphids when they can't use all of the sugar taken from plants.) The ants feed on this honeydew and protect the aphids in return, often keeping their eggs through the winter in their nests. In the spring, the ants transport the aphids to host plants and then protect them from enemies.
Natural enemies play an important part in controlling aphids. Lady beetles, lacewings, damsel bugs, flower fly maggots, certain parasitic wasps, birds, and fungal diseases all attack aphids.
There are a number of methods used in controlling aphids:
- Ladybugs prey on aphids, control small infestations and can be encouraged to come to your garden.
- Hose aphids off of infested plants with a heavy spray of water, taking care not to use so much pressure that it will injure delicate plant parts.
- Prune off and destroy heavily infested plant parts.
- For a step up from water, aphids can be controlled organically with of insecticidal soaps. Insecticidal soaps are non-toxic and safe to use in backyards. Please follow manufacturer instructions for application for the safest and best results.
