Fiorinia externa

Ferris, 1942

elongate hemlock scale

Fiorinia externa, the elongate hemlock , is an to Japan and southern China. Accidentally to North America around 1908, it has become established throughout the northeastern United States and threatens hemlock (Tsuga) and related conifers. The is a pupillarial scale, with females remaining within their second- . Heavy cause yellowing, premature needle drop, branch dieback, and occasional tree death. It poses particular economic concern for Fraser fir Christmas tree production in the southeastern United States, where it can persist on harvested trees for up to 13 weeks post-harvest.

Fiorinia externa 1122009 by Eric R. Day, Virginia Polytechnic Institute and State University. Used under a CC BY 3.0 us license.

Fiorinia externa 1122010 by Eric R. Day, Virginia Polytechnic Institute and State University. Used under a CC BY 3.0 us license.

Fiorinia externa 5019025 by Pennsylvania Department of Conservation and Natural Resources - Forestry Archive,. Used under a CC BY 3.0 us license.

Pronunciation

How to pronounce Fiorinia externa: //fi.oˈɾi.ni.a ɛkˈstɛr.na//

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Identification

females are approximately 1 mm long. The second- female cover is elongated, about 1.5 mm long, and yellowish- to reddish-brown in color. male scale covers are . and are yellowish; when crawlers settle, they excrete white filaments that can give infested foliage a whitish appearance. The is distinguished from other Fiorinia species by the elongated shape of the female scale cover and its specific association with conifer .

Images

Habitat

Coniferous forests and plantations, particularly those dominated by hemlock (Tsuga), fir (Abies), and spruce (Picea). In its North range, it occurs in eastern hemlock stands, Fraser fir Christmas tree farms, and ornamental conifer plantings.

Distribution

to Japan and southern China. and established in the northeastern United States, with records from New York (first reported 1908) south to Georgia, and west to Michigan, Kentucky, and Tennessee. Isolated records exist from California and Florida on imported material, and from England on a single imported fir tree where it did not establish.

Seasonality

occurs as within pupillarial females or as mature females. Eggs hatch in spring, with migrating to new needles. One or two per year occur in North America; where only one generation completes, a partial second generation may begin but with high winter mortality.

Diet

Phloem-feeding sap-sucker; feeds on sap from conifer needles using a long tube.

Host Associations

Tsuga canadensis - primary eastern hemlock, most common in North America
Tsuga caroliniana - primary Carolina hemlock
Tsuga diversifolia - primary northern Japanese hemlock
Abies amabilis - Pacific silver fir
Abies fargesii - Farges fir
Abies veitchii - Veitch fir
Abies fraseri - Fraser fir, economically important Christmas tree
Picea pungens - Colorado spruce

Life Cycle

Pupillarial : female remains within second- . stages are within the pupillarial female or fully mature adult females. Eggs hatch in spring; are the mobile stage. Crawlers settle on new needles and secrete filaments. There may be one or two per year in North America.

Behavior

disperse to new needles on the same or are carried longer distances by wind or birds. In post-harvest Christmas trees, crawler increases when trees are moved indoors due to warmer temperatures and water availability. Baling trees for shipping reduces crawler emergence compared to unbaled trees, likely due to restricted airflow.

Ecological Role

and forest pest; contributes to decline of eastern hemlock stands in the northeastern United States. Natural caused by (including Conoideocrella luteorostrata, bassiana, lecanii) have been observed in . with Tsugaspidiotus tsugae (hemlock woolly ) has been documented, with F. externa competitively superior.

Human Relevance

Serious pest of ornamental and forest conifers; of particular economic importance to Fraser fir Christmas tree production in North Carolina, Virginia, and Tennessee. Heavy reduce tree quality and marketability. Post-harvest survival on cut trees creates regulatory concerns for interstate transport and risk of introduction to new areas. Chemical control uses or ; efforts have focused on , though poor synchrony between Encarsia citrina and F. externa in North America limits effectiveness compared to Japan.

Similar Taxa

Tsugaspidiotus tsugaealso feeds on eastern hemlock; distinguished by woolly covering and different
Fiorinia phantasmacongeneric on palms; distinguished by association and geographic range
Fiorinia fioriniaecongeneric on palms in Florida; requires microscopic or molecular identification for separation