- Aphids do a lot more damage than you
sometimes called greenfly, are small insects that
suck plant juices from stems and leaves and can
severely stunt or even kill their host plants.
Early detection and control with insecticidal soap
are the keys to managing aphids in greenhouses,
house plants, gardens, and landscapes.
Jack DeAngelis, PhD
OSU Ext. Entomologist
Identification of aphids
Aphids are small, soft-bodied insects
that feed exclusively on plants. These small
insects can be nearly colorless to green, yellow,
pink and even black in color. They can form dense
colonies on leaves and stems (right) sometimes
completely obscuring the plant surface. Most
aphids are wingless but a few individuals in a
colony may have wings.
Aphids occur on nearly all plants, their
populations can build quickly and their effects
can be severe. Aphids feed by inserting tube-like
mouth-parts into the plant's vascular system and
withdrawing plant sap. Plant sap is a complex
mixture of water, sugar and a small amount of
To get enough of the protein that they
need aphids must take in a lot more sugar (plant
sap) than they can use -- excess sugar is expelled
through the body as a concentrated sugar solution
called honeydew. This honeydew may drip
from the plant and attract sugar-loving insects
like ants and wasps.
|aphids on a stem, notice
single aphid above and a colony below; photo
by Elizabeth DeAngelis
While aphids feed on plant sap, they may
inject their host plant with toxins that deform
plant tissue. This is why plants are often twisted
and deformed above where aphids are feeding.
Aphids can be found on both above-ground stems,
buds and leaves and below-ground roots and
common misspellings and misnomers for
aphids: plantlice, plant lice, greenfly, green
fly, green bug, aphis
Natural aphid control in gardens
Aphids have a wide range of natural
enemies. Predators like syrphid fly larvae,
lady beetle adults and larvae, and lacewings as
well as parasitic wasps, and others, are important
in aphid control. The typical cycle is for an
aphid colony to build rapidly in spring
followed by a rapid decline in summer after the
colony is discovered by a predator. Sometimes more
than one type of natural enemy will "work" a
colony at the same time.
Aphids are important pests in gardens,
greenhouses as well as in commercial agriculture.
Accurate identification of pest species is both
difficult and extremely important a natural
control program and therefore has gotten
considerable research attention. The following is
an excellent in-depth resource: Aphids on the
World's Crops: An Identification and Information
Guide, 2nd Edition (2000)by R.
L. Blackman, V. F. Eastop. (more information).
Because aphids are somewhat host plant
specific these pests rarely spread from one type of
plant to a completely unrelated species. It is
unlikely that widely different crops will be
affected by the same aphid species. The more usual
situation is that certain crops will consistently
have aphid infestations while others seem to remain
relatively free of these pests.
Chemical & physical control of aphids
For small greenhouses and home gardeners
the best chemical control is insecticidal
soap. The guidelines for controlling aphids
are the same as those for spider mites,
using strong overhead watering and insecticidal
soap. See Using
Insecticidal Soap and Spider
Mite Control for details about this method.
The best physical control is the
use of row covers (see Related
Articles below) early in the season where
they are practical. Row covers are made of a thin,
strong, non-woven fabric that allows light, water
and air to get in but excludes flying pests like
aphids, leaf-feeding beetles and thrips. They work
great in greenhouses and over garden rows. Place
row covers, loosely, early in the season before
aphids and other pests get started.
Aphid control on indoor plants
Plants growing indoors, both house plants
and greenhouse-grown plants, often are plagued by
aphids because they are physically separated from
their natural enemies which normally keep their
numbers in check. Lacking any natural enemies
aphid populations can grow rapidly and even kill
plants. Once you find aphids, or detect
their activity by the sticky honeydew they
produce, you should take quick action.
First, rinse plants with a spray of
water. Large plants can be taken outdoors, in
summer, and rinsed with a garden hose. Once
thoroughly rinsed to remove as many aphids as
possible, spray thoroughly with a 1-2%
solution of insecticidal soap (see links
above and below). Use genuine insecticidal soap
not household soaps as these can burn plants.
After 30 minutes, rinse plants again to remove
soap residues. You may need to repeat this
procedure several times a year. See Aphids
and Spider Mites On House Plants for more
Don't forget to bookmark us for next time - press
ctrl-D in most browsers.
Mission: To provide accurate, up-to-date and
unbiased information for solving common insect and
mite problems around your home, business and landscape
using least-toxic methods.
Please see the Disclaimer
statements as well.
Copyright © 2004-...
LivingWithBugs, LLC. All rights reserved.