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Fiorinia Scale (Elongate Hemlock Scale)

Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org
Fiorinia externa Ferris. The elongate hemlock scale, sometimes known as the fiorinia scale, is a serious armored scale insect pest of hemlock, Tsuga spp., on ornamental and forest trees in our area. The principal host plants include eastern hemlock, T. canadensis , Carolina hemlock, T. caroliniana , and northern Japanese hemlock, T. diversifolia , fir, Abies spp ., and spruce, Picea spp . This key pest also feeds on cedar, Cedrus spp ., Douglas-fir, Pseudotsuga menziesii , pine, Pinus spp ., and yew, Taxus spp ., but these are not preferred hosts. These less preferred host plants, if infested, are usually growing adjacent to infested hemlocks.

The waxy covers of this species can be observed on the lower needle surface as well as on new cones. The flattened, elongate, light yellow brown to brownish orange waxy cover of the adult female is about 1.5 mm long. The adult female's body beneath the waxy cover, eggs, and crawler stage are yellow. The white, waxy cover of the male is smaller. When closely examining infested hemlock needles, adult males may look like tiny wasp parasitoids as they crawl across the needles. Adult male scales only have one pair of wings. Sometimes waxy secretions from settled crawlers may build into a mass of tangled strands. These waxy strands may be so abundant that it gives the lower surface of infested needles a white appearance. When this condition is present, it may cause uninformed individuals to misdiagnose this as hemlock woolly adelgid.

Scales injure host plants by inserting their threadlike, piercing-sucking mouthparts into needles and withdraw vital nutrients necessary for plant growth from mesophyll cells. Armored scale insects do not feed on the contents of vascular cells. Excessive loss of plant fluid reduces the growth and health of the plant. Feeding injury causes needles to develop yellow banding on the top of infested needles. This injury causes needles to drop prematurely giving the crown of an infested tree a thin appearance. Frequently, this key pest is found on the same hemlock tree with hemlock woolly adelgid, Adelges tsugae . There are several key insect and mite pest species that feed on hemlock foliage. It's important to accurately identify what pest species or causal organism is present when maintaining the health of hemlocks. An infestation of this armored scale weakens trees allowing successful attack by secondary organisms such as the hemlock borer, Melanophila fulvoguttata , or Armillaria root rot.
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