Most plants can tolerate low numbers of aphids without noticeable damage.

Aphids are very small, soft-bodied insects. They have pear-shaped bodies with long legs and antennae, and most species have two tube-like structures called cornicles protruding from their hind end. Under certain conditions some species can produce adult forms with wings.

• Tolerate low to moderate numbers of aphids as long as they aren't causing noticeable plant damage. There is a reason for this: aphids have many natural enemies such as spiders, ladybugs, lacewings, and minute parasitoids ("mini-wasps") that often keep aphid numbers below damaging levels. These beneficial insects rarely appear on the scene until after aphids have begun attacking plants. This "lag-time" can be a day or two or as long as several weeks. As the season progresses, aphid control by these natural enemies improves because more natural enemies are attracted to your garden and more stay to breed.
• Aphids commonly found on trees will not infest your garden annuals, and these aphids can help attract natural enemies that will attack pests on other plants.

• Learn to recognize beneficial insects. Among the most important natural enemies of aphids are the mini-wasps ("parasitoids") that lay their eggs inside the bodies of aphids. These tiny wasps cannot sting people. A parasitized aphid (called a "mummy") looks puffed-up, and its skin hardens and changes color, often to tan, light brown, or black.
• Attract beneficials to your garden by planting a wide variety of flowering plants. (See "Naturally Managing Pests . . . With a Healthy Garden"). The adult forms of many beneficial insects, including mini-wasps and lacewings, feed on pollen and nectar.
• Consider buying beneficial insects (see the Resources section below). Lacewings are more likely to stay in your garden than commercially available ladybugs.
• Buy beneficials before aphid numbers are high. If you have an aphid emergency, first use soap or oil sprays (see the Resources section below) to reduce the population. Then, if necessary, release natural enemies. On the other hand, don't purchase beneficial insects before you have aphids. You will be releasing them into your garden to starve.
• Wipe off or prune away colonies of aphids from leaves and buds.
• Use a forceful stream of plain water to wash off aphids and honeydew.
• Use insecticidal soaps to kill aphids on contact and spare beneficials such as lacewings. These products do not leave toxic residues.
• Use spray (horticultural) oils to control aphids without leaving toxic residues for natural enemies.

• Use slow-release fertilizers. Some aphids reproduce more quickly on plants with high levels of nitrogen in their leaves and buds. Fertilizers such as compost, sewage sludge, or encapsulated materials (Osmocote®) are better because they slowly release moderate levels of nutrients.
• Avoid excessive pruning because it stimulates aphid-attracting growth.
• Use a row cover (Tufbell®) to exclude aphids and other pests but allow air, light, and irrigation water to reach plants.
• Control ants by spraying or painting a 4" wide sticky barrier (Tangle-foot®, Stickem® Tree Pest Barrier) around woody shrubs or trees. (See the Ant fact sheet in this series.)

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