Cycad Poliaspis Scale | Poliaspis media Maskell

California Pest Rating for
Cycad Poliaspis Scale | Poliaspis media Maskell
Hemiptera: Diaspididae
Pest Rating: B



Initiating Event:

Poliaspis media has recently been found in the environment of Orange and San Diego counties and is presently assigned a temporary rating of “Q”.  A pest rating proposal is required to determine a permanent pest rating.

History & Status:

Background:  Poliaspis media is a polyphagous armored scale insect that feeds on the undersides of leaves of host plants1.  The scale insect’s feeding induces galls on some host plants1.  Some of the known hosts are: Achariaceae: Melicytus alpinus1; Aizoaceae: Disphyma australe1; Araliaceae: Raukaua anomalus1; Asteliaceae: Astelia fragrans1; Asteraceae: Craspedia sp.1, Ozothamnus sp.1, Sonchus sp.1; Brassicaceae: Streptanthus sp.1; Cycadaceae: Cycas circinalis1, Cycas revoluta1; Ericaceae: Acrothamnus colensoi1, Cyathodes sp.1, Dracophyllum latifolium1, Dracophyllum lessonianum1, Dracophyllum oliveri1, Dracophyllum recurvum1, Dracophyllum sp.1, Dracophyllum traversii1, Leptecophylla juniperina1, Leucopogon fraseri1, Leucopogon sp.1, Pentachondra pumila1; Gaultheria depressa1, Gaultheria rupestris1, Gaultheria sp.1; Myrtaceae: Leptospermum scoparium1; Orchidaceae: Orchidaceae sp.1; Plantaginaceae: Veronica decumbens1, Veronica elliptica1, Veronica hulkeana1, Veronica macrantha1, Veronica pentasepala1, Veronica subalpina1, Veronica venustula1; Podocarpaceae: Lepidothamnus laxifolius1; Primulaceae: Myrsine australis1, Myrsine divaricata1, Myrsine salicina1, Samolus repens1; Ranunculaceae: Clematis afoliata1; Restionaceae: Emposidisma minus1; Rubiaceae: Coprosma arborea1, Coprosma chathamica1, Coprosma cheesemanii1, Coprosma depressa1, Coprosma propinqua1, Coprosma pumila1, Coprosma rhamnoides1, Coprosma robusta1, Coprosma rubra1, Coprosma sp.1, Coprosma spathulata1, Coprosma tenuifolia1, Coprosma virescens1; Rutaceae: Leionema nudum1; Santalaceae: Exocarpos bidwillii1; Thymelaeaceae: Pimelea prostrata1, Pimelea urvilleana1; Zamiaceae: Dioon edule1Poliaspis media may be transported long distances when infested plants or fresh plant parts are moved.

Worldwide Distribution: Poliaspis media was described from specimens collected in New Zealand before 1880, but it may be native to Asia1,2.  It has been found in New Zealand, Fiji, India, Greece, the United Kingdom, and the United States1.  It was first found in Florida in 20072.

Official Control: Poliaspis media is listed as a harmful organism by Japan and the Republic of Korea3.

California Distribution Poliaspis media was collected in the environment of California at a residence in Tustin (Orange County) in 1999 and at a residence in Villa Park (Orange County) in 2016 and again in 2017.  It was found at a park in San Diego County in 2018.

California Interceptions Since 1993, samples of Poliaspis media have been collected 22 times in inspections of nurseries in San Diego, Orange, Los Angeles, and Santa Barbara counties.  The scale insects were also intercepted once on a shipment of sago palms (Cycas revoluta) from Florida.

The risk Poliaspis media (cycad poliaspis scale) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Poliaspis media is established in nations with Mediterranean climates similar to much of California and it is expected to establish a widespread distribution here. It 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: Poliaspis media is known to feed on a variety of plants in 21 families. It receives a High (3) 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: Scale insects have high reproductive rates and may disperse long distances when infested plants or plant parts are moved.  They may also be spread by wind or by hitchhiking on plants, animals, or equipment.  Poliaspis media 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: Poliaspis media is not expected to lower any crop yields.  It may lower the value of nursery stock by disfiguring plants with its presence.  It is listed as a harmful organism by several of California’s trading partners and could potentially disrupt markets for nursery stock and other fresh plant material.  Poliaspis media receives a Medium (2) in this category.

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

B, C

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: Poliaspis media is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  It is not expected to affect threatened or endangered species or disrupt critical habitats.  It might trigger new treatment programs in the nursery industry and by residents who find infested plants unsightly.  Cycads are high value, slow-growing ornamental plants that are popular in California and may be significantly impacted by this insect.  Poliaspis media receives a High (3) in this category.

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

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:

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 Poliaspis media (Cycad Poliaspis Scale):  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: Poliaspis media is only known to be established in the environment of Orange County. It receives a Low (-1) 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)


Over the course of 20 years, Poliaspis media has been found multiple times in nurseries in California but it has only been intercepted coming into the state once.  It has been found in the environment of Orange and San Diego Counties.  There have been no recent formal surveys for this pest.  It is possible that this scale insect is more widely established in the environment of Southern California and is infesting nurseries locally.

Conclusion and Rating Justification:

Poliaspis media has been established in the environment of Orange County for several years, was recently found in San Diego County, and is not under official control.  It is expected to have significant impacts on the nursery industry and ornamental plantings as it expands its distribution in the state.  A “B” rating is justified.


1 Miller, Dug, Yair Ben-Dov, Gary Gibson and Nate Hardy.  ScaleNet.

2 Hodges, Greg and W.N. Dixon. 2007.  The Poliaspis Cycad Scale Poliaspis cycadis Comstock (Hemiptera: Diaspididae): A new exotic scale insect for Florida.,_The_Poliaspis_Cycad_Scale.pdf

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

Responsible Party:

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

Comment Period:* CLOSED

1/24/18 – 3/10/18


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Pest Rating: B


Posted by ls