Aphids

Aphids are one of the most common pest insects in the garden and are actually one of the easiest to control without using pesticides. There are over 4,000 species of aphids and most have specific plants they like to feed upon. The adults are very small - on average about 2 mm in length, and about the size and shape of a sesame seed. Aphids vary in colour: white, various shades of green, pink, rusty-red or black. The many species have similar life cycles.  The eggs hatch in the spring and females give birth to young with repeated generations occurring every two weeks.  Winged aphids migrate to new host plants.

Symptoms:

Both foliage and fruits can be injured by these piercing-sucking insects.  Evidence of their activity is indicated by curled, twisted, stunted leaves. Aphids also produce a sticky substance called honeydew. The honeydew can drip off larger plants like trees, and may blacken which is caused by a sooty mold fungus. Aphids can also transmit viral diseases in potato, raspberry or rhubarb. 

Control:

• There are many natural enemies of aphids such as beneficial lady beetles, syrphid fly (hoverfly), lacewings, soldier beetles, parasitic wasps and many others. Both the adults and the larvae of many beneficials eat aphids.
  • Never use insecticides in the garden as this will kill beneficial insects too.
  • Mulch all bare soil with a natural shredded wood mulch or shredded leaves to provide habitat for beneficial insects. Check out our Mulch and More pamphlet for more information.
• A fine, hard spray of plain water is very effective in knocking aphids off the plant and in most cases, kills them too. Wingless aphids cannot climb back up the plant, so they starve to death. No soap is necessary. In fact, soaps can injure some plants. Monitor your plant and repeat daily. They aphids will be gone in no time at all. For a demo of how to wash off aphids, see below.
• Avoid giving your plants too much fertilizer, especially nitrogen which encourages leafy succulent growth which makes feeding easier and more attractive to aphids.
• If plants are dense or over-crowded, consider thinning to encourage better air circulation.
• Silver plastic mulch has been shown to be effective in repelling aphids, whiteflies and other insects. Any silver material such as aluminum foil, foil pie plates, or thin, silver emergency camping blankets will do. Place the silver mulch at the base of plants and secure with soil or rocks to prevent it from blowing away. 
• Remove weeds near plants which can be alternate hosts for aphids.
• Ants sometimes "farm" aphids, especially in trees.

Sources:

Pests in gardens and landscapes: Aphids. (n.d.). Retrieved March 29, 2021, from http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html

Williams, S.; Skinner, H. (2011). Gardening, naturally: A chemical-free handbook for the Prairies. Regina, Saskatchewan: Coteau Books.