Gray Scale | Pseudoparlatoria ostreata

California Pest Rating for
Gray Scale | Pseudoparlatoria ostreata Cockerell
Hemiptera: Diaspididae
Pest Rating: A



Initiating Event:

Pseudoparlatoria ostreata was reported to be established on the island of Oahu, Hawaii (J. Matsunaga, pers. comm.).  It is currently Q-rated, and a permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background:  The scale cover is thin and circular in adult female P. ostreata.  These scales can form dense aggregations on host plants.  Pseudoparlatoria ostreata is reported to feed on (apparently causing damage to plants, in some cases) plants in 39 families, including Agavaceae (Agave sp.), Arecaceae (various palms), Cactaceae, Caricaceae (Carica papaya), Euphorbiaceae (including Acalypha spp.), Fabaceae, Orchidaceae (various orchids), and Vitaceae (Vitis sp.).  (Malumphy & Redstone, 2012; Sweezey, 1945; Wolff, 2008).  In agricultural situations, this scale is reported to be a pest of papaya (J. Matsunaga, pers. comm.; Miskimen & Bond, 1970; Wolcott, 1948) avocado (McKenzie, 1935), and Acalypha species (Dekle, 1965; Wolcott, 1948).  It appears to be primarily tropical and subtropical, but it has managed to become a pest in greenhouses in temperate areas (in the United Kingdom, for example) (Malumphy & Redstone, 2012).

Worldwide Distribution:  Pseudoparlatoria ostreata is native to the Caribbean and has been introduced to North America (Mexico, Florida, and Texas), Central America (Guatemala), South America (Argentina, Brazil, Chile, Ecuador, and Venezuela), Hawaii, Africa, and Europe (indoor plantings only) (Claps et al., 2001; Claps et al., 2006; García et al., 2016; Malumphy & Redstone, 2012; J. Matsunaga, pers. comm.; Sweezey, 1945).

Official Control: Pseudoparlatoria ostreata is considered a prohibited, declared pest in Australia (Government of Western Australia).

California Distribution:  Pseudoparlatoria ostreata is not known to be present in California.

California Interceptions:  Pseudoparlatoria ostreata was intercepted in 2012 at a California border station on palms from Mexico (BL0P06030809).

The risk Pseudoparlatoria ostreata would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Most of the areas where Pseudoparlatoria ostreata is known to occur have a subtropical or tropical climate. For example, in the United States, it is restricted to Florida, Texas, and Hawaii.  However, some locations (for example, in Argentina) have a more temperate climate (Claps et al., 2001).  This scale is highly polyphagous, and suitable host plants are probably present over much of California.  It appears possible that Pseudoparlatoria ostreata could become established in a significant portion of California.  Therefore, it receives a Medium (2) in this category.

– 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: Pseudoparlatoria ostreata is highly polyphagous, and has been reported to feed on plants in 39 families. Therefore, it receives a High (3) in this category.

– 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: It is apparent that Pseudoparlatoria ostreata is easily transported on infested plant material, as it has been introduced to many locations.  In addition, another species in this genus, parlatorioides (Comstock), has a high reproductive capacity (females lay up to 130 eggs) and is suspected to be parthenogenic, and this may apply P. ostreata as well (Miller & Davidson, 2005).   Therefore, it receives a High (3) in this category.

– 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 Pseudoparlatoria ostreata became established in California, it could become a pest of many different crops because it is so polyphagous.  Avocados and grapes are known hosts, but there could be many more.  Infestations of this scale could increase production costs and affect normal cultural practices.  As scales are easily transported with infested plant material, the presence of this scale in California could also result in the loss of markets because of the phytosanitary risk to an area importing California plants or plant products.  Therefore, it receives a High (3) in this category.

Economic Impact:  B, C, D

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.

Economic Impact Score: 3

– 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: Pseudoparlatoria ostreata is a polyphagous scale insect that has been documented to cause damage to plants through its feeding. It is possible that this scale could directly affect rare plants.  There are rare California plants in some of the plant families that are hosts of this scale, for example, Shaw’s agave (Agave shawii), which occurs in southern, coastal California (Calflora).  If this scale becomes established in California, it is also likely to impact ornamental plantings and it could trigger treatments as well.  Therefore, it receives a High (3) in this category.

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

Environmental Impact:  B, D, E

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:

Environmental Impact Score: 3

– 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 Pseudoparlatoria ostreata: High (14)

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: Pseudoparlatoria ostreata is not known to be present in California.  It receives a Not established (0) in this category.

–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 (14)


The distribution of Pseudoparlatoria ostreata appears to be mostly limited to areas with a subtropical or tropical climate, although there are a few locations that suggest this scale could survive in a more temperate climate.  Therefore, there is some uncertainty regarding its ability to become established in a significant portion of California.  There is little uncertainty regarding the presence of suitable host plants in California, because this scale is highly polyphagous.

Conclusion and Rating Justification:

Pseudoparlatoria ostreata is a polyphagous scale that has a demonstrated ability to attack a wide variety of plants and cause damage.  It is not known to be present in California, and if it became established in this state, there is a significant possibility that it could have economic and environmental impacts.  For these reasons, an “A” rating is justified.


Calflora: Information on California plants for education, research and conservation, with data contributed by public and private institutions and individuals, including the  Consortium of California Herbaria.  [web application].  2017. Berkeley, California: The Calflora Database [a non-profit organization].  Accessed 28 December 2017.

Claps, L.E., Wolff, V.R.S, & González, R.H.  2001.  Catálogo de la Diaspididae (Hemiptera: Coccoidea) exόticas de la Argentina, Brazil, Brasil y Chile.  Revista de la Sociedad Entomológica Argentina.  60 (1-4): 9-34.

Claps, L.E., Zamudio, P., & Briz, L.D.  2006.  Las Dactylopiidae y Diaspididae (Hemiptera, Coccoidea) de la Colecciόn Kenneth Hayward, Tucumán, Argentina.  Revista Brasileira de Entomologia.  50 (1): 33-38.

Dekle, G.W.  1965.  Florida armored scale insects.  Arthropods of Florida and Neighboring Land Areas.  3:  1-265.

García, M.M., Denno, B.D., Miller, D.R., Miller, G.L., Ben-Dov, Y., & Hardy, N.B.  2016.  ScaleNet: A literature-based model of scale insect biology and systematics.  Database. doi: 10.1093/database/bav118.  Accessed 28 December 2017.

Government of Western Australia.  Department of Primary Industries and Regional Development.  Pseudoparlatoria ostreata Cockerell, 1892.  Accessed: 27 December 2017.

Malumphy, C. & Redstone, S.  2012.  Grey scale Pseudoparlatoria ostreata Cockerell (Hemiptera: Diaspididae), a pest of indoor plantings new to Britain.  Entomologist’s Gazette.  63: 107-114.

Miller, D.R. & Davidson, J.A.  2005.  Armored scale insect pests of trees and shrubs.  Comstock Publishing Associates.  Ithaca, NY.  442 pp.

McKenzie, H.L.  1935.  Biology and control of avocado insects and mites.  University of California Agricultural Experiment Station Bulletin.  592: 1-48.

Miskimen, G.W. & Bond, R.M.  1970.  Scientific Survey of Porto Rico and the Virgin Islands.  Volume XIII – Part I.  The New York Academy of Sciences.  New York, NY.  114 pp.

Sweezey, O.H.  1945.  Insects associated with orchids.  Proceedings of the Hawaiian Entomological Society.  12(2): 343-403.

Symbiota Collections of Arthropods Network.  Accessed 20 November 2017.

Wolcott, G.N.  1948.  The insects of Puerto Rico.  The Journal of Agriculture of the University of Puerto Rico.  20(1): 1-224.

Wolff, V.R.S.  2008.  Revisão de Pseudoparlatoria (Hemiptera, Diaspididae).  Iheringia Série Zoologia.  98(3): 291-307.


Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741;[@]

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211,[@]

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4/19/18 – 6/3/18


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Pest Rating: A


Posted by ls