White Prunicola Scale | Pseudaulacaspis prunicola

California Pest Rating for
Pseudaulacaspis prunicola (Maskell) | White prunicola scale
Hemiptera: Diaspididae
Pest Rating: A


Initiating Event:

In 2018, this scale was found in Solano County on Ligustrum sp. bonsai that had been purchased in Fresno County.  This scale currently has a Q-rating.  A permanent pest rating proposal is required to support an official pest rating.

History & Status:

Background:  Pseudaulacaspis prunicola is a polyphagous scale that is reported to feed on plants in 15 families.  Among the recorded hosts are fruit and ornamental trees, including Carica, Malus, and Prunus species (Agnello et al., 2015; Follett, 2000; Miller and Davidson, 2005).  Death of trees can result from feeding by this scale (Miller and Davidson, 2005).

There is some uncertainty regarding the species identity of P. prunicola.  This scale was considered a synonym of P. pentagona until 1980.  Kreiter et al. (1999) reported individuals in a single population that could be identified morphologically as either species.  Pseudaulacaspis pentagona is an A-rated (by CDFA) pest that is highly polyphagous and is reported to cause damage to a wide variety of plants, including peaches in the southeastern United States and papaya in Hawaii (Branscome, 1999; Follett, 2000).

Worldwide Distribution:  Pseudaulacaspis prunicola is thought to be native to temperate China or Japan (Miller and Davidson, 2005).  It has been introduced to Europe, the eastern United States, and Hawaii.  In the eastern United States, it is reported from Florida north to Massachusetts (Miller and Davidson, 2005).

Official Control: Pseudaulacaspis prunicola does not appear to be under official control in any country.  However, P. pentagona, which has been considered by some to be a senior synonym of P. prunicola, is a regulated pest in some countries (EPPO Global Database, 2018).

California Distribution:  Although P. prunicola has been collected at times in the state, this species does not appear to be established in California.

California Interceptions:  The P. prunicola found on Ligustrum sp. bonsai in Solano County in 2018 represents the only interception of this species in California.

The risk Pseudaulacaspis prunicola would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Pseudaulacaspis prunicola has proven itself capable of becoming established in a variety of climates, and it is highly polyphagous.  It could probably establish a widespread distribution in California.  Therefore, prunicola receives a High (3) 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: Pseudaulacaspis prunicola is reported to feed on plants in at least 15 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 Reproductive and Dispersal Potential: Pseudaulacaspis prunicola is likely to be transported via movement of infested plants.  Therefore, it receives a Medium (2) 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: Pseudaulacaspis prunicola is reported to attack fruit and ornamental trees.  Feeding damage is reported to cause death of trees.  Infestations of this scale could lower crop yield and increase production costs.  Therefore, it receives a Medium (2) in this category.

Economic Impact: A, B

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: 2

– 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: This scale is reported to kill ornamental trees.  Infestations could trigger treatment programs.  Therefore, it receives a High (3) in this category.

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

Environmental Impact: 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.

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 Pseudaulacaspis prunicola: 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: Pseudaulacaspis prunicola 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:

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


There is taxonomic uncertainty regarding P. prunicola and P. pentagona; they have been considered to be the same species.  As P. pentagona is A-rated and is also not known to be present in California, the main implication of this uncertainty appears to be that the potential impact of P. prunicola could be greater than that considered in this PRP because there are additional hosts and additional climatic niche space reported for P. pentagona.

Conclusion and Rating Justification:

Pseudaulacaspis prunicola is a highly polyphagous scale that is not known to be present in California.  It has the potential to cause economic and environmental impacts in the state if it was to become established.  For these reasons, an “A” rating is justified.


Agnello, A., Jentsch, P., and Kain, D.  2015.  Prebloom problemas.  Scaffolds Fruit Journal 24:1-3.

Branscome, D.  1999.  Pseudaulacaspis pentagona.  Accessed October 2, 2018: http://entnemdept.ufl.edu/creatures/orn/scales/white_peach_scale.htm

California Department of Food and Agriculture.  Pest and damage record database.  Accessed September 28, 2018:

EPPO Global Database.  2018.  Accessed October 4, 2018: https://gd.eppo.int/

Follett, P. A.  2000.  Arthropod pests of papaya in Hawaii.  Chronica Horticulturae 40:7-10.

Kreiter, P., Panis, A., and Tourniaire, R.  1999.  Variabilite morphologique chez Pseudaulacaspis pentagona Targioni Tozzetti dans une population du sud-est de la France (Hemiptera: Diaspididae).  Annales de la Société Entomologique de France 35:33-36.

Symbiota Collections of Arthropods Network.  Accessed September 27, 2018:

Miller, D. R. and Davidson, J. A.  2005.  Armored scale insect pests of trees and shrubs (Hemiptera: Diaspididae).  Cornell University Press, Ithaca, NY.

Responsible Party:

Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741, plant.health[@]cdfa.ca.gov

Comment Period:* CLOSED

12/6/2018 – 1/20/2019


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Pest Rating: A

Posted by ls