Universally loathed, particularly when they make their way into a salad bowl, aphids feed on a wide range of domestic and commercial crops. The green peach aphid (Myzus persicae) is a common pest in western Oregon, afflicting more than 100 of our plants, including staple garden vegetables like cabbage and kale.
Pros and Cons: Small insect-eating birds, like bushtits, feed on aphids, as do beneficial insects such as hoverflies, green lacewings, and certain parasitic wasps. So on the plus side, aphids’ presence encourages these helpful birds and insects in your garden.
But that’s about the only virtue these critters can claim. Aphids weaken plants by sucking juices from their tissues, sometimes spreading disease. They reproduce at an alarming rate in May and June—each female can produce three to six fully formed young per day for weeks on end. Many aphids also attract small ants that “farm” the aphids, protecting them from predators in exchange for the sweet honeydew the aphids excrete. This honeydew forms a sticky residue on plants’ leaves, which leads to unsightly black mold that can interfere with photosynthesis.
Battle Plan: Most disease and insect threats affect plants that are already weak or stressed. So if you have aphids, consider the plants’ overall health and address any problems with soil, light, or other conditions. To treat the problem, first dislodge the aphids with a strong stream of water—they’re not very savvy at finding their way back. Then, count on birds and predatory insects to do their job. If that doesn’t work, step things up and plant alyssum and coriander, whose flowers will attract and provide nectar for aphid-eating hoverflies.