California Pest Rating for
Wasmannia auropunctata (Roger): Little Fire Ant
Pest Rating: A
PEST RATING PROFILE
Wasmannia auropunctata is regularly intercepted by CDFA and is presently assigned a temporary rating of “Q”. A pest rating proposal is required to assign a permanent pest rating.
History & Status:
Background: Wasmannia auropunctata is a common tramp ant species notorious for its painful and long-lasting sting1. These tiny ants nest under leaf debris, rotten limbs, stones, in the crotches of trees, in clumps of grass, and behind the sheaths of palms1. An entire colony can establish inside a macadamia nut shell2. The ants are highly adaptable and do well under wet or dry conditions and in open or shady areas1. They feed on honeydew, dead arthropods, small animals, live insects, and forage in homes for oily foods1. Wasmannia auropunctata can easily spread long distances hidden in plants, logs, greenwaste, gravel, and even cars2.
Worldwide Distribution: Wasmannia auropunctata is native to a large region that spans from central Argentina to southern Texas4. From there it has spread throughout the Caribbean, to parts of tropical Africa, and to Hawaii and other Pacific islands4. It was first found in Florida in 1924 and Hawaii in 19994.
Official Control: Wasmannia auropunctata is listed as a harmful organism by Bermuda, French Polynesia, Japan, and Taiwan3.
California Distribution: Wasmannia auropunctata has not been found in the environment of California except for possibly in 19374.
California Interceptions: Wasmannia auropunctata has been intercepted 46 times by CDFA’s high risk programs and border stations. Most interceptions have been on cut flowers, fruit, and plants from Hawaii and Florida.
The risk Wasmannia auropunctata would pose to California is evaluated below.
Consequences of Introduction:
1) Climate/Host Interaction: Wasmannia auropunctata is found primary in warm climates. It has been present in Florida for more than 90 years but has not spread beyond the southern half of the state. It is native to southern Texas but has not spread. Wasmannia auropunctata will probably be limited to southern and coastal California. It 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: Wasmannia auropunctata is a generalist forager that can feed on a wide variety of sources. 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: Ants are capable of rapid reproduction and can disperse long distances when colonies or queens are moved. Wasmannia auropunctata 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: Wasmannia auropunctata is not expected to lower crop yields or increase crop production costs. It is listed as a harmful organism by several of California’s trading partners and could cause trade disruptions as a contaminating pest on a wide variety of commodities. It is not expected to vector other pestiferous organisms. Wasmannia auropunctata is known to tend honeydew producing insects and may consume parasitoids, disrupting biological control of pests. They are also known to be attracted to eyes for moisture2. Stings associated with this behavior sometimes lead to epidemics of blindness in animals2. This may lead to changes in cultural practices in livestock production. The ants are not expected to interfere with water supplies. Wasmannia auropunctata 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: Invasive ants such as Wasmannia auropunctata may cause slow, long-term ecological changes that have potential to lower biodiversity, disrupt natural communities, or change ecosystem processes. They may also trigger new treatment programs by residents who find infestations and the associated stings and blind pets unacceptable and in the nursery and livestock industries. This may lead to significant impacts on cultural practices. Wasmannia auropunctata 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 Wasmannia auropunctata (Little Fire Ant): 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: Wasmannia auropunctata is not known to be present 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.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (14)
There are already other invasive tramp ant species established in California. These other ants may preclude some of the economic and environmental impacts of Wasmannia auropunctata.
Conclusion and Rating Justification:
Wasmannia auropunctata is not known to be present in California and is expected to have significant economic and environmental impacts if it were to establish in the state. An “A” rating is justified.
1 Brooks, Shawn and J.C. Nickerson. Common name: little fire ant. University of Florida Featured Creatures. http://entnemdept.ufl.edu/creatures/urban/ants/little_fire_ant.htm
2 Little Fire Ant: Wasmannia auropunctata. http://hdoa.hawaii.gov/pi/files/2014/05/2014-LFA-Brochure.pdf
3 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). https://pcit.aphis.usda.gov/pcit/
4 Wetterer, James K. 2013. Worldwide spread of the little fire ant, Wasmannia auropunctata (Hymenoptera: Formicidae). Terrestrial arthropod reviews 6: 173-184. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=13&ved=0CGoQFjAM&url=http%3A%2F%2Fwww.researchgate.net%2Fprofile%2FJames_Wetterer%2Fpublication%2F257645059_Worldwide_spread_of_the_little_fire_ant_Wasmannia_auropunctata_%2528Hymenoptera_Formicidae%2529%2Flinks%2F02e7e5258d69a288fd000000.pdf&ei=2VokVdW3KYfBgwSqwIGYCw&usg=AFQjCNF29YvMf8xw_JFsjIN_lj5aEincAg&bvm=bv.89947451,d.eXY
Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.
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Pest Rating: A
Posted by ls