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Aphids

General Facts

Also known as plant lice, aphids cause more damage to cultivated plants than any other insect. With about 1,350 species of aphids in North America, most types of crops, garden plants, houseplants, trees, and decorative shrubs can be at risk.

Appearance / Identification

Aphids are tiny insects measuring 4 to 8 mm in length with soft, pear shaped bodies. Their colour can vary from pale green, black, red, or cloudy white. Depending on the season, these pear-shaped pests may be winged or wingless.

Habitat

Aphids can be found throughout North America. While they attack many plant species, common hosts include the coniferous and deciduous trees that grow across Canada. Aphids live on or near the plants they eat and collect under leaves and sheltered areas.

Diet

Aphids feed on plant sap. They pierce leaves and stem surfaces and suck up the sap (juice) from the plants. They can feed on any part of a plant but they prefer new plant growths. As they feed, aphids produce a sweet, sticky substance known as honeydew which attracts ants and other insects to the plant; it can also cause fungal growth on the plant surfaces, which is detrimental to the plant. Since they often feed in large groups, aphid infestations can quickly destroy gardens and flowerbeds.

Life Cycle / Reproduction

Aphids have a complex reproductive cycle. The first aphids of the year hatch from eggs during the spring. This generation of females reproduces through self-cloning until their host plant is crowded. The next generation develops with wings and flies off to find another plant. At the end of summer, all aphids return to their original host to lay eggs for the next year. While they may only live for one to six weeks, each female aphid can produce as many as 12 young per day.

Problems Caused by Aphids

Plants attacked by aphids often suffer stunted growth, low crop yields, and even death. The pests also leave large heaps of sticky, shiny sugars called honeydew on sidewalks, cars, or other objects under their feeding area. Besides creating a mess, honeydew may also grow black mould and attract other pests like ants, bees, flies, and wasps. Additionally, aphids can spread dozens of plant diseases.

Detection / Signs of Infestation

Aphids often cause leaves to spot, yellow, curl, or wilt. Galls may also form on plant stems and branches. Check the undersides of leaves, the tips of branches, or new plant growth to find aphids. In addition, gardeners can look on the soil under infested plants for aphids’ cast-off skins, which look like small white flakes.

Prevention Tips

Even small aphid problems can grow to overwhelm homeowners, so prevention is key. To keep winged aphids away from houseplants, repair screens and weather stripping around doors and windows. The best way to spot and stop infestations is to inspect plants often during the growing season. Before bringing plants inside or adding them to gardens, always check for aphid colonies.

Control / Removal

Adding plants that repel the pests, such as coriander, basil, catnip, chives, and dill, is another way to help protect at-risk gardens. Sweet alyssum, yarrow, or herbs in the carrot family can also attract helpful bugs like lady beetles, lacewings, and flies that eat aphids. For the most effective and reliable solutions, contact local pest professionals.

There are appropriately registered and labeled insecticides for controlling these pests. If they have invaded an indoor structure, you should consult a professional, licensed pest control provider to control the infestation. For outdoor plant infestations, you can consult your local garden centre.