Information on aphids can also be seen on the Healthy Canadians website.
Aphids are small, soft-bodied, pear-shaped insects with long antennae and a pair of cornicles (short tubes) sticking out on either side of their stomachs. Their see-through bodies are usually green, red, black, yellow or white.
Aphids are common garden pests. These tiny creatures have hundreds of species and almost as many colours.
Aphids have an unusual lifecycle. In the spring, hibernated eggs hatch into females that give birth to 10 or more live female young each day. This allows a colony of aphids to grow very quickly, especially indoors. In the fall, the males are born and the fertilized females produce eggs for hibernating outdoors. These shiny black eggs are tucked into the crevices of bark and bud scales.
Winged adults are produced only when the colony must migrate, like when the colony is overcrowded or the climate is unfavourable.
Although aphid damage is easiest to spot on ornamental, fruit and shade trees, they can also infest flower and vegetable gardens.
You will find aphid colonies on the underside of leaves, the tips of branches or anywhere there is new growth. An initial infestation of aphids is usually localized, but can spread quickly if allowed to develop unchecked. Aphids damage plants by sucking the sap from leaves, twigs, stems or roots and can sometimes spread plant virus diseases in the process.
Leaves attacked by aphids have spotty yellow discolourations, usually on the undersides. The leaves may later dry out and wilt or curl. Some species of aphids cause plants to form galls (swellings of plant tissues that are globe or spindle-shaped). The galls, which often turn brown, contain many aphids in all stages of development.
When aphids moult, they cast off their skins, which look like small white flakes.
Many aphid species produce large amounts of "honeydew", a sweet sap that makes leaves shiny and sticky, accumulating on anything found under infected trees or plants. Because of its sweetness, aphid honeydew attracts other pests like ants, flies and wasps. The honeydew can also predispose an affected plant to develop black sooty mould, making the leaves appear dirty and grey.All of these factors contribute to making the aphid a pest. To keep damage to a minimum, it is important to control an aphid infestation in the early stages.
Try to attract the natural enemies of aphids by planting a variety of flowering plants. Small-flowered plants like sweet alyssum, yarrow and herbs in the carrot family are often visited by insect species that prey on aphids, like the lady beetle, the lacewing and syrphid flies. Parasitic wasps are also attracted to these flowers.
Some natural predators or parasites can be bought from specialized suppliers and certain garden and greenhouse supply stores. Follow instructions carefully if buying these biological control products.
Aphid infestations may also be treated with pesticides. There are many active ingredients registered for domestic class use on aphids. Insecticidal soap sprays, which must be in direct contact with the insects, may also be effective and leave no residual effect.
Tall heavily infested trees may be hard to treat without special equipment. For infestations bad enough to threaten the health of a tree, you may want to hire a licensed pest control operator.