Aphids are small pear-shaped insects (Image 1) that can be found in many colors such as green, yellow, red, gray and black (Images 2,3,4). They feed by sucking sap from buds, leaves, twigs and developing fruit, often in dense groups (Image 3).
Adult aphids are usually wingless but can form wings when populations are high, when food source deteriorates, or in the fall. They have many generations per year, often seen together (Image 3). Some lay eggs to overwinter, others can give birth to live young (Image 5) in times of plenty or under stress. There is no pupal stage and can reach reproductive stage in as little as 8 days.
Sap passes through the body and is ejected out the rear of the body. This material is called “honeydew” and is very sticky. A sign of aphids is sticky material found dripping off plants onto cars, patio furniture and more. Honeydew can become black with sooty mold fungus. Another sign can be the presence of ants (Image 4) which will protect the aphids, because they eat the honeydew.
Lady beetles eat aphids (Image 6) so their presence in high numbers can indicate aphids. Lady beetle nymphs (Image 7) can be kind of scary but they also eat aphids so they are a benefit.
Control of aphids can be done with many products. Many are contact sprays which need to be sprayed on all parts of the plant, top and bottom (underside of leaves). Because many beneficial insects like to eat aphids, always spray very early in the morning (before 8 am in most cases).
The BEST spray for aphids is insecticidal soaps and oils makes it one of the best choices for aphid control in most cases. These products kill primarily by smothering the aphid, so thorough coverage of infested foliage is required.
Many other insecticides are available to control aphids in the home garden and landscape, including foliar-applied formulations of malathion, permethrin, and acephate (nonfood crops only). While these materials may kill higher numbers of aphids than soaps and oils, their use should be limited, because they also kill the natural enemies that provide long-term control of aphids and other pests, and they are associated with bee kills and environmental problems. Repeated applications of these materials may also result in resistance to the material.
Systemic insecticides are also available for aphid management, primarily for woody ornamentals. These materials, including imidacloprid, are very effective and are especially useful for serious infestations of aphids such as the woolly hackberry aphid, which is often not effectively controlled by biological control or less toxic insecticides. Imidacloprid can have negative impacts on predators, parasitoids, and pollinators, so its use should be avoided where soaps and oils will provide adequate control. To protect pollinators, don't apply imidacloprid or other systemic insecticides to plants in bloom or prior to bloom.