Fiorinia externa Ferris: Elongate Hemlock Scale

California Pest Rating for
Fiorinia externa Ferris:  Elongate Hemlock Scale
Hemiptera:  Diaspididae
Pest Rating:  A

Initiating Event:

Fiorinia externa is often intercepted by CDFA and presently has a temporary rating of “Q”.  A pest rating proposal is required to determine a permanent pest rating.

History & Status:

BackgroundFiorinia externa is an armored scale insect that is considered to be a pest of ornamental and forest conifers1.  These insects overwinter as mated females or eggs1.  Females begin laying eggs within their waxy covers in early spring1.  As eggs hatch, crawlers disperse to other needles on the same plant where they settle on the underside1.  There they insert their mouthparts and feed1.  They reach maturity in 7-8 weeks in Pennsylvania1.  Feeding causes needles to develop yellow banding and drop prematurely1.  This damage causes foliage to appear thin and weakens the trees, making them vulnerable to secondary invaders1.  Known hosts include 43 species2 including: CupressaceaeBiota orientalis5, Juniperus chinensis5 (Chinese juniper), Juniperus rigida5 (temple juniper); PinaceaeAbies spp.1,3 (firs), Cedrus spp.1 (cedars), Picea spp.1,3 (spruces), Pinus spp.1,3 (pines), Pseudotsuga menziesii1,3 (douglas fir), Tsuga canadensis1,2 (eastern hemlock), T. caroliniana1,2 (Carolina hemlock), and Tsuga diversifolia (northern Japanese hemlock); Taxaceae: Taxus spp.1 (yews).   Fiorinia externa may be carried long distances when infested plants or plant parts are moved.

Worldwide Distribution: Fiorinia externa is native to Japan1,2 and is also found in China5.  It was first found in New York in 19081 and has since been found in Connecticut, Maryland, Massachusetts, New Jersey, Ohio, Rhode Island, Virginia, and the District of Columbia.  Interceptions by CDFA also indicate that the scale is also established in North Carolina.

Official Control: Neither Fiorinia externa nor Fiorinia spp. are known to be under official control by any other states or nations4.

California DistributionFiorinia externa has never been found in the environment of California.

California InterceptionsFiorinia externa was intercepted 97 times between January 1, 2000 and December 31, 2014 by CDFA’s high risk inspections, dog teams, and other quarantine programs.  Most of the interceptions have been on fraser fir (Abies fraseri) from North Carolina.

The risk Fiorinia externa (elongate hemlock scale) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Species of Abies, Picea, Pinus, Pseudotsuga, Taxus, and Tsuga are native to the forests of California and are grown as ornamentals. Fiorinia externa is likely to establish wherever these host plants are grown.  Elongate hemlock scale receives a High (3) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Fiorinia externa is known to feed on 43 species of plants in 9 genera in three plant families.  It receives a Medium (2) in this category.

Evaluate the host range of the pest. Score:

Low (1) has a very limited host range.

Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential: Female elongate hemlock scales produce an average of 20 eggs during their lifetime and a generation may be completed every seven to eight weeks during the growing season1.  Crawlers typically remain on the same plant but may be dispersed long distances by wind or by hitchhiking on clothing, animals, or equipment.  They may also be carried long distances when infested plants or plant parts are moved.  Elongate hemlock scale receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

High (3) has both high reproduction and dispersal potential.

4) Economic Impact: If Fiorinia externa were to enter California it is likely that the scale would lead to lower yields and increased production costs in managed forests, Christmas tree farms, and in the nursery industry.  The scale is not expected to disrupt markets, change cultural practices, vector other pestiferous organisms, injure animals, or interfere with water supplies.  Elongate hemlock scale receives a Medium (2) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact: The establishment of Fiorinia externa in California would be likely to disrupt natural communities, as it infests forests and increases the susceptibility of trees to other pests and diseases.  The scale is not expected to directly affect any threatened or endangered species or disrupt critical habitats.  Elongate scale insect is likely to trigger additional treatment programs in managed forests, Christmas tree farms, and the nursery industry.  The scale is also likely to significantly impact cultural practices and ornamental plantings.  Fiorinia externa receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

Low (1) causes none of the above to occur.

Medium (2) causes one of the above to occur.

High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Fiorinia externa (elongate hemlock scale): High (13)

Add up the total score and include it here.

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Fiorinia externa has never been found in the environment and receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.

Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (13)


Impacts on forests may potentially be more significant than loss of trees.  Stands of dead trees may affect the rate of runoff and water supplies and could affect the stability of mountain and canyon slopes.  There have not been any recent formal surveys of the scales of conifers in California.  It is possible that Fiorinia externa could be present in some localities.

Conclusion and Rating Justification:

Elongate hemlock scale (Fiorinia externa) has never been found in the environment of California and would likely have significant economic and environmental impacts if it were to enter the state.  An “A”-rating is justified.


1 Hoover, Gregory A. 2009. Elongate Hemlock Scale (Fiorinia externa Ferris) Fact Sheet.  Pennsylvania State University.

2 McClure, Mark S.  Pest Alert: Elongate Hemlock Scale.  USDA Forest Service Northeastern Area NA-PR-01-02

3 Elongate Hemlock Scale Fiorinia externa Ferris.  PSU Christmas Tree Pest Fact Sheets.

4 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD).

5 SEL Catalog Query results for Fiorinia externa Ferris.

Responsible Party:

Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211,[@]

Pest Rating:  A

Posted by ls