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Shelterbelt Centre Pest Leaflets
Pine Needle Scale
Hosts: Scots pine, Colorado spruce, white spruce and other pines and spruces.
Appearance and Life Cycle: Pine needle scale is a microscopic insect that
overwinters as an egg under the scale formed by the mother. Nymphs emerge in early June and
search for suitable feeding sites on old needles. In 3 to 4 weeks the male nymphs form a narrow,
white, waxy protective scale about 1.5 mm in length. Meanwhile the females remain as free-
feeding insects without a scale covering. During the next 3 weeks the males develop into winged
adults and emerge from the scales to mate with the wingless females. By mid-August the
females produce a smooth, white, oblong shaped scale about 3 mm in length. Each female
produces about 40 overwintering eggs under the protective scale. There is one generation per
year.
Damage: Pine needle scale causes damage by inserting its mouthparts into
the needle and extracting sap. This feeding causes a yellowish-green area to form around each
puncture. In severe cases yellow spots merge, needles drop prematurely and the tree assumes a
dull, unhealthy appearance. A severe infestation would be 20 or more scales per spruce needle
and 50 or more per pine needle. Trees with repeated heavy infestations have reduced vigor and
annual growth and become more susceptible to secondary insects.
Control: Lady beetles, parasites and weather contribute to the natural control
of the scale. When natural controls fail, serious damage can be prevented by applying
insecticides. Insecticides recommended include: dimethoate, malathion, diazinon or carbaryl.
Two applications may be required; once in mid-June when nymphs are unprotected and
searching for feeding sites, and a second in early August to control the females before they
produce their protective scale covering.
For more information contact:
PFRA Shelterbelt Centre
Indian Head, Sask. S0G 2K0
Phone: (306) 695-2284 or Fax: (306) 695-2568
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