Aleurodicus dispersus Russell (Spiraling Whitefly)

California Pest Rating
Aleurodicus dispersus Russell (Spiraling Whitefly)
Hemiptera:  Aleyrodidae
Former Pest Rating:  Q
FINAL Pest Rating: A
Initiating Event:  

In October 2013, USDA released a DEEP report proposing to deregulate Aleurodicus dispersus (spiraling whitefly).  The insect is currently “Q”-rated by CDFA, so a pest rating proposal is needed to determine future direction.

History & Status:

Background:  Spiraling whitefly is highly polyphagous, feeding on plants in 49 different plant families.  Known hosts include such economically important pests as avocado, citrus, eggplant, pepper, rose, Prunus spp., and palms.  Interceptions indicate that the whitefly often moves long distances in the trade of plants and flowers.

Worldwide Distribution: The native range of spiraling whitefly is believed to be the tropical Americas.  It was described from Florida in 1965 from specimens collected as early as 1950.  Since then it has been found to have a widespread distribution including Hawaii, Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa, and Mexico.  Furthermore, it is reported in numerous nations in Central America, the Caribbean, South America, Europe and the Middle East, Africa, Asia, and Oceania.

Official Control: Arizona has a state quarantine against all citrus whiteflies.  Aleurodicus dispersus is also listed as a harmful organism by Antigua and Barbuda, Chile, China, French Polynesia, Grenada, Guatemala, Honduras, Israel, Japan, Jordan, Korea, Mexico, Morocco, and New Zealand2.

California Distribution:  Spiraling whitefly has not been found in the environment of California.

California Interceptions:  Spiraling whitefly is frequently intercepted on shipments of plants, leaves, and flowers from Hawaii and Florida.  It has been intercepted more than 1300 times since 11/29/2000.

The risk spiraling whitefly would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Spiraling whitefly has been present in Florida for over 60 years but has not spread beyond the central portion of the state. Primarily a tropical species, it is reportedly limited by cold temperatures.  In California the whitefly would likely be limited to southern and coastal areas.  Spiraling whitefly receives a Medium (2) 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: Spiraling whitefly is a highly polyphagous insect that is known to feed on plants from 49 different plant families.  The whitefly 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: Whiteflies reproduce rapidly and can be spread long distances by wind or through the movement of plants and flowers.  Spiraling whitefly 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: Spiraling whitefly was originally considered an economic pest in Hawaii when it was introduced.  However, damage is now limited as a successful biological control agent was introduced.  In the absence of this biological control agent in California, the whitefly may be expected to lower crop yield by both sucking juices from plants and reducing their photosynthetic capacity by contaminating leaf surfaces with sooty mold.  They may also lower crop value by triggering treatment and/or disfiguring nursery stock with their presence and with sooty mold.  Furthermore, Arizona maintains a quarantine against all citrus whiteflies and many of California’s trading partners list Aleurodicus dispersus as a harmful organism.  This could lead to disruptions in markets for California citrus.  Spiraling whitefly receives a High(3) 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: Rosa minutafolia (small-leaved rose) is listed as an endangered species in California and is a potential host for spiraling whitefly.  The whitefly may also trigger additional chemical treatments.  The whitefly 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 Aleurodicus dispersus (Spiraling Whitefly):  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: Spiraling whitefly has not been found in the environment of 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)

Uncertainty:

Spiraling whitefly has been intercepted more than a thousand times in California.  However, it has never been found in the environment.  This may indicate that environmental conditions in the state are unfavorable for establishment of the species.

Conclusion and Rating Justification:

In the absence of a successful biological control program in California, spiraling whitefly is expected to have significant economic and environmental impacts.  An “A”-rating is justified.

References:

1 Zlotina, Marina 2013.  Deregulation Evaluation of Established Pests (DEEP); DEEP Report on Aleurodicus dispersus Russell: Spiralling Whitefly

2 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD).  https://pcit.aphis.usda.gov/pcit/


Responsible Party:

Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.


Comment Period:  CLOSED

The 45-day comment period opens on Jun 22, 2016 and closed on Aug 6, 2016.


Comment Format:

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Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

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Pest Rating: A