Paracoccus marginatus Williams and Granara de Willink: Papaya mealybug

California Pest Rating for
Paracoccus marginatus Williams and Granara de Willink: Papaya mealybug
Hemiptera:  Pseudococcidae
Pest Rating:  A

Initiating Event:

February 26, 2014, USDA distributed a Deregulation Evaluation of Established Pests (DEEP) report proposing to change the status of Paracoccus marginatus, papaya mealybug, from actionable to non-actionable for the entire United States.  The insect is currently unrated by CDFA, so a pest rating proposal is needed to determine future direction.

History & Status:

BackgroundParacoccus marginatus is a polyphagous mealybug that feeds on at least 55 plant species in at least 18 families1.  Although papaya is the preferred host, other hosts include economically important crops such as citrus, avocado, cotton, cherry, tomato, and a variety of ornamentals1,2,3.  Infestations of the mealybug are typically observed as cotton-like clusters on the above ground portions of plants2.  Feeding can result in chlorosis, plant stunting, leaf deformation, early leaf and fruit drop, a heavy build-up of honeydew, and plant death2.   Paracoccus marginatus can move long distances through commerce in infested fruit, plants, or leaves.

Worldwide Distribution: Paracoccus marginatus is believed to be native to Mexico and Central America.  From there it has spread throughout the Caribbean, southern Asia, and to Benin, Ghana, Togo in Africa, and French Guiana in South America.  It was found in Florida in 1998, Puerto Rico in 2001, Guam in 2002, and Hawaii in 2004.   A greenhouse infestation in Illinois in 2001 was successfully controlled with biological control agents.

Official Control: Paracoccus marginatus is not known to be under official control in any states or nations.

California Distribution:  Paracoccus marginatus has never been found in the environment of California.

California Interceptions Paracoccus marginatus has been intercepted four times by California, on Plumeria rubra and betel from Hawaii, papaya from Mexico, and rambutan fruit from Honduras.  USDA has intercepted the mealybug nearly 650 times since 1994, mostly on fruit and other plant parts from Mexico destined for California1.

The risk Paracoccus marginatus (Papaya mealybug) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: The present distribution of Paracoccus marginatus is limited to USDA plant hardiness zones 10+. In California this corresponds with portions of the southern part of the state as well as greenhouses.  Papaya mealybug receives a Medium(2) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score: 2

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: Paracoccus marginatus is known to feed on 55 species of plants in at least 18 familes1.  It receives a High(3) in this category.

Evaluate the host range of the pest. Score: 3

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: Mealybugs reproduce rapidly; Paracoccus marginatus is thought to lay 100-600 eggs each and have up to 15 generations per year.  Mealybugs may be dispersed long distances by wind, as hitchhikers on clothing or animals, and through commerce in infested plants and plant parts.  Papaya mealybug receives a High(3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score: 3

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: Paracoccus marginatus is not reported to cause economic damage in Florida and has been successfully controlled by biological control on several Caribbean islands.  Papaya mealybug is not expected to lower crop yield, change normal cultural practices, vector other organisms, injure animals, or interfere with water supplies.  Although marginatus is not known to be listed as a quarantine pest by any nation, due to its limited worldwide distribution and frequent interceptions on fruit it is reasonable to conclude that it may disrupt some markets for fresh fruit exports.  It is also possible that the mealybug may increase crop production costs in the nursery and/or fruit industries by triggering additional treatments or disfiguring plants with their presence.  Papaya mealybug receives a Medium(2) in this category.

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

Economic Impact: 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.

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: Paracoccus marginatus is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  San Diego ambrosia (Ambrosia pumila) is a potential host of the mealybug and is listed as an endangered species.  The mealybug is not expected to disrupt critical habitats.  Papaya mealybug may trigger additional treatment programs in the nursery industry, fruit industry, and by some residents.  The mealybug receives a High(3) in this category.

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

Environmental Impact: B, D

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 Paracoccus marginatus (Papaya mealybug):  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: Paracoccus marginatus has never been detected in California 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)


It is likely that incursions of Paracoccus marginatus into California may have already occurred based on the large number of interceptions by USDA.  It is possible that the mealybug may already be present in parts of southern California.

Conclusion and Rating Justification:

The polyphagous nature and high frequency of Paracoccus marginatus interceptions make it likely that papaya mealybug will establish in southern California.  Economic impacts of the mealybug may include possible disruptions to fresh fruit exports as well as possible increased production costs in the nursery and fruit industries.  Potential environmental impacts include triggering new chemical treatments and direct feeding on endangered San Diego ambrosia.  An A-rating is justified.


1Landry, Cynthia.  2014.  Deregulation Evaluation of Established Pests (DEEP); DEEP Report on Paracoccus marginatus Williams and Granara de Willink: Papaya mealybug.

2Walker, Alison, Marjorie Hoy, and Dale Meyerdirk.  2006.  Papaya mealybug.  University of Florida Featured Creatures.

3Sakthivel, P., Karuppuchamy, P., Kalyanasundaram, M. & Srinivasan, T. 2012. Host plants of invasive papaya mealybug, Paracoccus marginatus (Williams and Granara de Willink) in Tamil Nadu. Madras Agricultural Journal 99(7-9): 615-619.

Responsible Party:

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

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Pest Rating:  A

Posted by ls