How to identify and control Aphids in the Garden
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, (not to be confused with “jumping plant lice” or true whiteflies) are small sap-sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions. The damage they do to plants has made them enemies of farmers and gardeners the world over, but from a zoological standpoint they are a very successful group of organisms. Their success is in part due to the asexual reproduction capability of some species.[not verified in body]
About 4,400 species of 10 families are known. Historically, many fewer families were recognised, as most species were included in the family Aphididae. Around 250 species are serious pests for agriculture and forestry as well as an annoyance for gardeners. They vary in length from 1 to 10 millimetres (0.04 to 0.39 in).
Natural enemies include predatory ladybirds, hoverfly larvae, parasitic wasps, aphid midge larvae, crab spiders, lacewings and entomopathogenic fungi like Lecanicillium lecanii and the Entomophthorales.
What Are Aphids?
Aphids seem to find their way into every garden. They are small, soft-bodied insects that can survive in almost any zone. Aphids multiply quickly, so try to control them before reproduction starts. Many generations can occur in one season. The good news is that they tend to move rather slowly and are relatively easy to control.
Aphids are tiny (about 1/32” to 1/8”), and often invisible to the naked eye. Various species can appear white, black, brown, gray, yellow, light green, or even pink! Some may have a waxy or woolly coating. They have pear-shaped bodies with long antennae; the nymphs look similar to adults. Most species have two short tubes (called cornicles) projecting from their hind end. Adults are usually wingless, but most species can develop a winged form when populations become crowded, so that when food quality suffers, the insects can travel to other plants, reproduce, and start a new colony. Aphids usually feed in large groups, although you might occasionally see them singly or in small numbers.
Nymphs and adults feed on plant juices, attacking leaves, stems, buds, flowers, fruit, and/or roots, depending on species. Most especially like succulent or new growth. Some, such as the green peach aphid, feed on a variety of plants, while others, such as the rosy apple aphid, focus on one or just a few plant hosts.
- Look for misshapen, curling, stunted, or yellow leaves. Be sure to check the undersides of leaves, aphids love to hide there.
- If the leaves or stems are covered with a sticky substance, that is a sign that aphids may have been sipping sap. The honeydew, a sugary liquid produced by the insects as waste, can attract other insects, such as ants, which gather the substance for food. When aphids feed on trees, their honeydew can drop onto cars, outdoor furniture, driveways, etc.
- The honeydew can sometimes develop a fungal growth called sooty mold, causing branches and leaves to appear black.
- Aphids feeding on flowers or fruit can cause them to become distorted.
- Some aphid species cause galls to form on roots or leaves.
- Aphids may transmit viruses to certain plants, and also attract other insects that prey on them.
How to Get Rid of Aphids
- Try spraying cold water on the leaves, sometimes all aphids need is a cool blast to dislodge them.
- Use commercially available biological controls or by spraying with insecticidal soap or horticultural oil.
- You can often get rid of aphids by wiping or spraying the leaves of the plant with a mild solution of water and a few drops of dishwashing detergent such as Ivory.
- Stir together 1 quart of water, 1 tsp of liquid dish soap and a pinch of cayenne pepper. Do not dilute before spraying on plants.
- In a spray bottle combine 2 parts rubbing alcohol, 5 parts water, and 1 tablespoon liquid soap.
- Organic controls include alcohol spray (isopropyl alcohol, straight or diluted), soapy emulsion (can be mixed w/alcohol), horticultural oil (read the directions) and pyrethrum spray. Soapy water/alcohol should be reapplied every 2-3 days for 2 weeks.
- You can also purchase beneficial insects, such as lady beetles and parasitic wasps, which will feed on aphids. These are usually ordered via mail—check the Internet for labs.
- Bring beneficial insects to your garden by adding plants that attract them. For example, nasturtiums are a good plant to rid your garden of aphids.