Paracoccus gillianae and Pseudococcus inconstans (formerly variabilis and sp. a): Agave Mealybugs

California Pest Rating for

Paracoccus gillianae and Pseudococcus inconstans (formerly variabilis and sp. A): Agave Mealybugs

Hemiptera: Pseudococcidae

Pest Rating: C

PEST RATING PROFILE

Initiating Event:

Two species of mealybugs have been found outdoors in California and are often found during nursery inspections of agave plants. The two insects, Paracoccus gillianae and the undescribed Pseudococcus sp. A (the A is for agave), are presently assigned a temporary rating of “Q”. A pest rating proposal is required to assign a permanent pest rating.

History & Status:

Background: Nothing is known of the biology of the agave mealybugs except that they appear to be mostly limited to agave in nurseries.

Worldwide Distribution: Unknown, possibly native to the southwestern United States or Mexico. The species appear to be moving about in the nursery trade. Specimens of Paracoccus gillianae have been collected in nurseries in seven counties in Florida and have been found outdoors at the Jacksonville Zoological Gardens in Duval County².

Official Control: The agave mealybugs are not known to be under official control anywhere in the world.

California Distribution: In California Pseudococcus sp. A was found outdoors in Los Angeles and Santa Barbara Counties in the 1980’s and 1990’s. It was found outdoors again in San Diego County in 2012 (PDRs 1326984 and 1401481). Paracoccus gillianae was found outdoors in Riverside County in 2012 (PDRs 1590291 and 1590292).

California Interceptions: Paracoccus gillianae and Pseudococcus sp. A have both been found in nurseries many times. USDA intercepted Paracoccus gillianae on plants from Mexico at Nogales in 1952 and San Diego in 1974. CDFA intercepted Paracoccus gillianae on plants that originated in Mexico in 2008 (PDR 1357956).

The risk agave mealybugs would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Agaves are popular in the nursery industry in California. Agave mealybugs are presumed likely to establish in residential areas where agaves are grown ornamentally and in desert ecosystems where native agaves grow. The agave mealybugs receive a Medium(2) rating for 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: The agave mealybugs appear to feed primarily on agave plants (Agave spp.). There are also records from other plants in the Agavaceae: Pseudococcus sp. A on aloe (PDR 1554869) and Paracoccus gillianae on Hesperaloe sp. and Yucca sp. The agave mealybugs receive a Low (1) rating for 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: Mealybugs can reproduce quickly but do not fly and therefore do not usually disperse far from their original host plant. However, mealybugs may be dispersed long distances by wind, by hitchhiking on animals or clothing, or by commerce in infested plants. The agave mealybugs receive a High (3) rating for 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: The agave mealybugs have never been documented to cause economic damage anywhere, but dense infestations are unsightly and have been seen killing patches of leaf. Pseudococcus sp. A. has been found on the agave produced commercially for tequila production in Mexico. However, they are not documented as economic pests in their native range. Some nurseries are treating their agaves to prevent contamination by the mealybugs, increasing production costs. The agave mealybugs receive a Low (1) rating for 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: A widespread establishment of the agave mealybugs may result in increased pesticide use by nurseries and residents. Nurseries in Santa Barbara County have had difficulty in eradicating infestations using topical insecticide treatments resulting in repeated applications to get them under control. Other nurseries are using systemic insecticides to prevent the mealybugs from showing up on their agaves¹. Therefore, if the rating were changed for the agave mealybugs it is expected to reduce pesticide use. There are no plants in the genera Agave, Aloe, Hesperaloe, or Yucca listed as threatened or endangered plants in California. There are no reports of agave mealybugs causing environmental damage anywhere in the world. The agave mealybugs receive a Low (1) rating for 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 Agave Mealybugs: Low (8)

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: Agave mealybugs have been found in the environment of Los Angeles and Santa Barbara Counties. They receive 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: Low (7)

Uncertainty:

It is possible that the agave mealybugs could have a wider host range than is known, resulting in greater consequences from establishment. It is also likely that the mealybugs have spread to other states where Agavaceae grow.

Conclusion and Rating Justification:

The agave mealybugs Paracoccus gillianae and Pseudococcus sp. A have been found outdoors in California and appear to be established in the nursery system. They do not appear to be causing any economic damage (other than through their quarantine status). They are not expected to have significant environmental impacts to California. A C-rating is justified for these pests.

References:

¹http://www.xericworld.com/forums/showthread.php?t=2831

²Von Ellenrieder, Natalia and Ian C. Stocks. 2014. A new species of mealybug in the genus Paracoccus Ezzat & McConnell from North America (Insecta: Coccoidea: Pseudococcidae). Zootaxa 3873(1):025-036.