Managing Aphid Pests

Aphids are commonly found on roses, vegetables, ornamental shrubs or fruit and shade trees. They're not always a problem – some plants are damaged very little by them.

Aphids can damage leaves or new growth which may weaken a plant. Some can spread plant viruses, and most aphids secrete honeydew as they feed, which leaves a sticky coating on leaves and fruit.

Using Natural Enemies

The best long-term solution is to let native predatory insects take care of the problem. Attract these beneficial insects to your garden by not using insecticides and planting flowers and herbs with your vegetables.

If you want to speed the disappearance of an aphid infestation:

• Avoid over-fertilizing plants with nitrogen because succulent growth attracts aphids
• Wash aphids off plants with a strong stream of water, repeating as needed
• Kill overwintering aphid eggs by spraying dormant oil on dormant fruit trees and shrubs (contact your local garden centre for information about timing)
• Early in the spring, release about 250 aphid midges (Aphidoletes aphidimyza) into your yard or small orchard – this native species is sold commercially in B.C.
• Spray horticultural oil for summer use on trees and shrubs during the growing season

Spraying Plants

Aphids can be difficult to control using sprays because:

• Survivors quickly develop new colonies
• They become resistant to insecticides that are used repeatedly

A useful tip is to use a registered insecticidal soap, but be sure to follow the instructions on the label.

As a last resort, try using a botanical insecticide that contains pyrethrins. Remember that insecticides are toxic so always wear protective clothing and rubber gloves. Always follow the directions on the label. Never use them near ponds or waterways because they will poison fish.