APHIDS ON
ORNAMENTALS
DESCRIPTION
Many species of Aphids or plant lice occur on ornamental
trees and shrubs in Pennsylvania. Certain species feed on
foliage, others on twigs and branches, flowers or fruit,
and some on roots. They feed on both coniferous and
deciduous plants. Effective control of Aphids has been a
problem to homeowners and landscape managers for years.
Some of the more common Aphids include the Green Peach
Aphid, Melon Aphid, Tuliptree Aphid, Giant Bark Aphid,
White Pine Aphid, and Rose Aphid. Aphids constitute a
large group of small, soft-bodied insects. They may
measure up to 6 mm in total length. Aphids have
piercing-sucking mouth parts which enable them to remove
plant fluids from a host. Aphids generally can be
recognized by their pear-like shape, a pair or cornicles
at the posterior of their bodies and fairly long
antennae. Aphids vary in color from green, yellow, red,
purple, brown or black.
LIFE CYCLE
The life history of many Aphids is complex and unusual.
Enormous populations of Aphids can be built up in a short
period of time. Although considerable variation occurs
between species, a typical life history is described as
follows. Aphids generally overwinter as fertilized eggs.
With the approach of Spring weather, the eggs hatch into
nymphs which rapidly mature into wingless females. Each
of these Aphids is responsible for producing a large
colony of Aphids and is referred to as a stem mother.
Stem mothers produce female nymphs without mating.
Successive wingless generations are produced until the
Aphid colony becomes overcrowded. When overcrowding
occurs, a generation of winged females is produced that
will migrate to other host plants. These winged females
are referred to as Spring migrants. Spring migrants
continue to produce successive generations until the end
of the Summer when winged males and females are produced.
The winged females return to the Spring host. They are
sometimes referred to as Fall migrants. These individuals
produce females which mate with males of the previous
generation. These mated females lay eggs that overwinter.
DAMAGE
Aphids are common, persistent, and sometimes troublesome
pests of ornamental plants. Most aphids cause damage to
host plants by robbing them of plant fluid, by the toxic
action of their salivary secretions injected during
feeding, and by serving as vectors of viruses that are
harmful to plants. Feeding by Aphids can stunt plant
growth, deform leaves and fruit, or cause galls on
leaves, stems and even roots. Many Aphids also excrete a
sticky, sugar-containing substance known as honeydew.
This material will drop onto the leaves, twigs, and fruit
of a plant. A black, sooty mold soon begins to grow on
this sugar-rich substrate. This mold not only mars the
appearance of the plant, but when abundant, will also
reduce the food-making process of a plant known as
photosynthesis. Honey dew is attractive to ants, flies,
hornets, and yellowjackets. It can also mar cars, chairs,
tables or other objects that are beneath Aphid-infested
plants.
CONTROL
Non-Chemical
In some cases, proper pruning, fertilizing, and watering
play an important role in preventing or suppressing an
Aphid infestation. Beneficial insects play an important
role in Aphid control. Ladybird beetles, lacewings, some
flower flies and tiny parasitic wasps will use Aphids as
a source of nourishment for their development. Remember
certain insecticide applications will destroy these
beneficial insects as well as the targeted pest species.
This practice could leave trees and shrubs unprotected if
pest populations should increase in the future.
Chemical
Formulations of acephate (Orthene), cyfluthrin (Tempo),
horticultural spray oil (Sunspray 6E, Sunspray Ultrafine
Spray Oil, etc.), insecticidal soap (M-Pede, Insecticidal
Soap, etc.) and malathion (Malathion) are labeled for
Aphid control.* Follow all label directions for specific
information on host plant label clearance, phytotoxicity
information, safety precautions and dosage information.
* See Woody Ornamental Insect, Mite and Disease Management, The Pennsylvania State University (2005) for more details.
WARNING: Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of reach of children, pets and livestock. Dispose of empty containers right away , in a safe manner and place. Do not contaminate forage, streams or ponds.
For professional assistance
with tree and shrub problems,
contact Keystone Tree Experts at (215) 348-4444.
