Aphids are small soft-bodied insects. They are one of the most common pest
groups of ornamental plants.
Click on the thumbnail image for the larger photo.
Aphids feed in colonies. They have plump, pear-shaped bodies and two tubes,
or cornicles, which project like exhaust pipes from their abdomens.
There are many species of aphids, and they feed on all types of vegetation.
The white pine aphid feeds on the bark of twigs and branches of Eastern white
pine. Heavy aphid infestations can seriously weaken small trees.
Aphid colonies may be found on young leaves, new succulent shoots, and twigs or
branches. Many vegetables and fruit trees, as well as ornamental plants, are
attacked. This species is the green apple aphid.
Aphid feeding often causes leaves to curl and become
deformed. Once this happens, control is very difficult because
aphids inside the curled leaves are protected from contact with
the insecticide. Some aphids are important vectors of plant
Aphids excrete a sugary waste produce called honeydew.
Notice the clear drop on the left side of this picture. Ants,
bees, and wasps collect honeydew for food. Black and brown
fungi, appropriately called sooty molds, cover leaves and other
objects below aphid colonies where honeydew collects. Sooty mold
problems can be prevented by controlling the resident aphids. A
variety of insecticides are registered for aphid control.
Some aphids produce a protective coat of white waxy
filaments. Woolly alder aphids feed and reproduce on silver
maple in spring and early summer, then produce winged forms which
migrate to alder to start new colonies. While not particularly
injurious to either of its hosts, this aphid can become a
nuisance because its white, woolly threads accumulate under
heavily infested trees.
This insect is commonly called the Hemlock Woolly Aphid
even though it is not in the scientific family of true aphids.
Its correct name is the Hemlock Woolly Adelgid. Underneath the
wax, adelgids resemble tiny, plump aphids without cornicles.
The pine bark adelgid is also commonly called an aphid.
Similar adelgids feed on spruce, larch, and other conifers.
Twigs, large branches, and trunks of heavily infested pine
trees may become nearly white with wax from pine bark adelgids.
though light infestations cause little damage, persistent heavy
infestations can seriously weaken a tree and may eventually lead
to its death. The same insecticides which are registered for
aphid control may be used on adelgids; however, the results are
not always satisfactory because their protective waxy coat
reduces the amount of insecticide which reaches the insect.