Download Scale Insects

Scale Insects
There are two general groups of
scales — the armored scale and the
soft scale. ARMORED SCALES
have a hard, protective covering of wax
under which the insect lives and feeds. It
is because of this covering that armored
scales are usually difficult to control.
Pine needle scale and euonymus scale are
examples of this type of scale.
SOFT SCALES have a soft, waxy
covering that is directly connected to the
insect's body. They secrete a sticky
substance called honeydew as they suck
the sap out of the tree. People often
complain that their tree is "dripping." It's
actually the scale that is making the mess
all over the cars and picnic tables! The
sticky surfaces often become blackened
by the development of black sooty mold.
Cottony maple scale and pine tortoise
scale are soft scales.
SYMPTOMS: Leaves are undersized
and discolored. If an infestation is severe,
A typical scale insect.
branches could die causing the plant's
canopy to thin and become severely weakened. These insects can be found on bark, twigs and
leaves or needles of plants. The specific location depends on the particular scale species and
its behavior (or "preference"). Scale insects can be one of the worst pests of trees and shrubs.
CA USE: Scales are sucking insects. Their mouthparts are needle-like tubes (stylets) and are
almost as long as, or longer than, their 1/16" to 1/8" long bodies. The stylets penetrate wood
or leaves to extract plant juices. The stage that hatches from the egg is called a crawler. This is
the dispersal stage and it leaves the protection of the dead female's scale cover in search of a
feeding site. This stage and the second instar nymph are most vulnerable to an insecticidal or
oil treatment. Because the occurrence of these stages varies, one needs to know the life cycle
of the scale.
The following plants are commonly infested by different scale species: arborvitae, lilac, ash,
maple, cherry, oaks, pine (Austrian & mugo), Euonymus spp., hemlock, juniper and yew.
SOLUTION: Most scales are difficult to control. A winter application of horticultural oil
plus one or two treatments during the growing season should be targeted for the vulnerable
stages. Control may take several years if the scale population is very large. Fertilization,
mulching, and watering will help increase your plant's resistance to scale attack and also
help it to recover if scales are already present.