At less than an eighth of an inch long, aphids are small but formidable adversaries in the vegetable garden.
These insects attack the tender growth of plants and feed by sucking on their juices.
A small infestation usually does not hurt a plant, but in large numbers, aphids can weaken a plant and make it susceptible to other problems.
Vegetable plants most frequently attacked by aphids are beans, cabbage, cucumber, melons, peas, potato, pumpkin, squash and tomato.
Recognizing aphid attacks
Aphids have soft, pear-shaped bodies and come in a variety of colors including green, yellow, pink, red, gray, black or brown.
Adults are generally wingless, but under certain conditions, winged forms can occur, allowing an aphid infestation to spread to other plants.
Because aphids are small and difficult to see, they often become a big problem before the gardener notices them. The following clues can indicate you have an aphid problem:
• As aphids feed, they inject saliva into the plant which causes leaves, stems and flowers to twist and curl.
• Aphids excrete a sweet liquid called honeydew which drips onto plant foliage. Honeydew encourages the development of black sooty mold and attracts honeydew-feeding ants that protect the aphids from predator attacks.
• As aphids grow, they shed their “skins” — cast skins serve as signs of current or past aphid presence.
Aphids produce many generations each year; adult females give birth to live young without mating.
In fall, aphids mate and the females lay eggs that can survive the winter. The eggs hatch in the spring as the weather warms, allowing the aphid population to start growing again.
What to do with aphids?
To prevent the introduction of these pests into your garden, eliminate nearby weeds which can serve as a home for aphids and inspect new plants carefully before bringing them into your garden.
In the fall, remove debris and dead plants from your vegetable garden to eliminate sites where aphid eggs may overwinter.
Because high levels of nitrogen encourage aphid reproduction, use slow-release or low-nitrogen fertilizers and only when your plant is in need of a fertilizer.
Check your garden weekly for aphids, looking for signs of an infestation on tender plant tissue. If you see aphids, act immediately.
If only a few leaves or shoots are affected, hand-wipe or prune out the affected plant parts.
A strong stream of water can be used to knock aphids off a sturdy plant.
Once on the ground, it is difficult for the aphids to return to the plant and they become easily susceptible to ground predators.
Spraying an aphid-infested plant with insecticidal soap kills aphids and their eggs on contact.
The distortion of leaves caused by aphids, however, can prevent the soapy water from reaching all surfaces of the leaves allowing some aphids to escape contact with the soap and, thereby, survive.
Other chemicals are available to control aphids. While these materials may kill higher numbers of aphids than soaps, their use should be limited because they also kill beneficial insects, some of which feed on the aphids and provide long-term control.
For more local gardening information, tune into KONP (AM 1450 and FM 101.7) at 1 p.m. on the last Monday of each month for a live, hour-long gardening show with host/moderator Todd Ortloff and veteran Clallam County Master Gardeners Judy English, Jeanette Stehr-Green and Bill Wrobel.
Pearl of Wisdom
A newly born aphid becomes a reproducing adult within a week of birth. As a result, aphid numbers grow rapidly.
Be on the lookout for aphids in your vegetable garden and implement control measures as soon as you see signs of an attack. A small infestation can rapidly become a large one.
Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener.
