Pine needle scale (Chionaspis pinifoliae) are very small, white, stationary insects found on the needles of pine (primarily ponderosa, Mugo and scotch), spruce and occasionally, balsam fir, hemlock, and yew. They feed by inserting their stylet into the needles and sucking the juices out. This causes spotting to the branches. Badly infested trees may have a greyish appearance with needle loss. Left uncontrolled whole branches can die.
Identification and Damage
Look for white, oblong, stationary insects on the needles. Feeding damage appears as small dead spots on the needles where they have remove the sap and chlorophyll. These spots can coalesce killing whole needles. Badly infested trees may have a greyish appearance with needle loss. Left uncontrolled whole branches can die.
Life Cycle
The insects overwinter as eggs beneath the dead mothers protective scales covering. The eggs hatch in May/June, some areas as late as July. Hatching time is temperature dependent, occurring between 298 and 448 growing degree days (Adams N.E. (n.d.)). The newly hatched nymphs (crawlers) are minute, oval in shape, and reddish in colour. They crawl to an open space on the needle and begin feeding. Their colour quickly changes to light brown/yellow and they flatten out. After this stage the life cycles of males and females differ.
In 3 to 4 weeks the male nymphs form a white protective scale over it’s self. 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. The impregnated females then build a protective scale over themselves (about 3 mm in length) and lay around 40 eggs. The female then begins shrinking and dies while the eggs overwinter beneath her and her protective scales covering. In some locations, a second generation may occur in early fall at 1388 to 1917 growing degree days (Adams N.E. (n.d.)).
Control
Natural Controls:
- Ladybugs and parasitic wasps
- Remove them by hand using a cue tip dipped in rubbing alcohol.
- Prune out heavily infested branches.
- Heavy rains at crawler stage can destroy some of these small fragile insects as will high temperatures.
Sprays:
- Dormant oil sprayed during dormancy (late winter/early spring).
- Summer oil (horticultural oil) sprayed at crawler nymph stage all the way until the adult female builds her scale.
- Malathion (not permitted for Ontario home gardeners).
Photo credit: Photo taken by the author.
References:
Adams N.E. (n.d.), (Extension Educator, Agricultural Resources) University of New Hampshire Cooperative Extension, ‘Using Growing Degree Days For Insect Management’, Retrieved on Jan. 23 from: http://ccetompkins.org/resources/using-growing-degree-days-for-insect-management
McGauley B. H and Kirby C. S. (revised 1991), Ontario Ministry of Natural Resources, ‘Common Pests of Trees in Ontario’, Retrieved on Jan. 25, 2021 from: https://www.svca.on.ca/downloads/Common_Pests_of_Ontario_s_Trees.pdf
Additional reading resources:
Missouri Botanical Garden, (n.d.). Pine needle scale. https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/scale/pine-needle-scale.aspx
Natural Resources Canada, (Date modified: 2015-08-04). Pine needle scale. https://tidcf.nrcan.gc.ca/en/insects/factsheet/5957
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