Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES
Pine Needle Scale
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The
pine needle scale, is, probably the most common armored scale found on
conifers in the United States and Canada. The white, oyster shell shaped
scales can completely cover needles, causing plant discoloration to needle
and branch death. Plants Attacked This
pest prefers pines, especially Scotch and Mugho, but it can infest other
pines, spruces, firs and Douglas-fir. Damage Heavy
infestations of pine needle scales remove considerable amounts of plant
juices resulting in yellowed needles. From a distance, trees appear frosted
or silvery. If heavy infestations are allowed to continue, twigs and branches
may die. |
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Description and Life Cycle
This
scale settles on the needles of its host and forms white, oyster shell-shaped
wax covers. These covers or armor are about 1/16 to 1/8-inch long when the
scales are fully grown and there is a yellowish spot, the exuvim,
on the small end. The male scales are usually smaller and more slender. This
scale over winters as deep reddish colored eggs protected under the female's
old armor. The eggs hatch in mid-May into tiny, flat nymphs called crawlers.
These pink crawlers {picture} creep to new places on the tree in order to find
suitable needles on which to feed. The crawlers are rather clumsy and they
often fall from the trees and may be blown onto nearby trees. Once settled on a
suitable needle, the crawler inserts its hair-like mouthparts, and begins to
form the new armor. After a couple of weeks, the nymph molts under the armor
and continues to increase in size for about three weeks. By this time male
scales are smaller and more slender than the females. The males molt into a pre-pupa
for a week before emerging as winged adults. The females, however, molt into
wingless nymph-like adults. After mating, the females continue to grow for a
couple of weeks before laying eggs under the armor. Females produce an average
of 40 eggs.
Two
generations of this scale occur. The over wintering eggs hatch in mid-May and
the summer produced eggs hatch in late July. Unfortunately, the eggs may hatch
over a period of two to three weeks.
Control Hints
This
scale normally is spread by crawlers being blown from tree to tree. Spread is
also more rapid when mature trees begin to touch branches. Scale crawlers may
also be spread by birds or animals which roost or brush against trees with
active crawlers. Early detection will prohibit spread and reduce the need for
extensive spraying.
Strategy 1: Biological Control - The twice-stabbed lady beetle,
a jet black beetle with two red spots and several parasitic wasps seem to
control the pine needle scale in forest stands. However, these biological
controls are often killed by the pesticides used for the control of other
insect pests. Careful monitoring of predators and parasites as well as using
pesticides with little effect on beneficials can
allow biological control to be successful.
Strategy
2: Chemical Control - Dormant Oil Sprays - Since these scales over winter as eggs, dormant
oil seems to have little effect. However, delayed dormant oil sprays applied at
the time that the eggs are about to hatch in May has produced satisfactory reduction
in scale populations.
Strategy
3: Chemical Control- Crawler Sprays - This is the time honored technique. Sprays will be
needed in a series of two or three sprays at seven day intervals.
Strategy
4: Chemical Control-Systemic Insecticides - Systemic insecticides are very effective against
young settled nymphs. Sprays should be applied after the crawlers have settled.
Information obtained through the Ohio State Extension Factsheet HYG-2053-95
Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES