Category Archives: Hymenoptera

Hymenoptera, Insects, Mites & Earthworms

Plebeia frontalis (Friese): Stingless Bee

California Pest Rating for
Plebeia frontalis (Friese): Stingless Bee
Hymenoptera:  Apidae
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

On September 12, 2013, Dr. Martin Hauser reported the tentative identification of Plebeia frontalis from specimens submitted from a nest found in an Ash tree in Palo Alto.  This is the first detection of this species in the United States.

History & Status:

Background:  Plebeia frontalis is a tropical stingless bee that typically nests in cavities in trees and logs.  P. frontalis is a eusocial insect that forms colonies of about 5,000 insects5.  Workers forage for pollen and nectar as a food source and to provision brood cells.  P. frontalis is documented to be a pollinator of coffee1, passion flower1, and avocado2 and may have been domesticated by Mayans for honey production3.  Colonies can have multiple queens and, when resources are plentiful, they will split and form a new colony typically 200m away5.  There are no documented pathways for the accidental human-assisted spread of these bees, but they could be transported in logs or other items with cavities suitable for a nest.

Worldwide Distribution: Plebeia frontalis has a Neotropical distribution that includes Mexico, Colombia, Costa Rica, Honduras, Nicaragua, and Panama4.

Official Control: Plebeia frontalis is not known to be under official control in any nation or state.

California Distribution:  Plebeia frontalis has been found nesting in a single tree in Palo Alto.

California Interceptions:  Plebeia frontalis has never been intercepted in a regulatory situation.

The risk Plebeia frontalis would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Plebeia frontalis is a tropical bee and is not expected to be cold tolerant. However, during cold weather the bees can be expected to shut down their reproduction and successfully overwinter in California5.  Its distribution in California would likely be limited to coastal and southern California.  frontalis 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: Plebeia frontalis nests in cavities and are generalist foragers on pollen and nectar of a wide range of flowering plants.  It may incorporate plant pieces into its colonies and at high densities may cause significant defoliation5.  When nectar is scarce the bees will pierce flowers and steal nectar, which can reduce the fitness of plants5.  It receives a High(3) rating 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: P. frontalis may have high reproductive potential under favorable conditions but does not have high dispersal potential.  Colonies can have multiple queens and when resources are plentiful they will split.  New colonies are typically 200m from existing colonies5.  Plebeia frontalis receives a Medium(2) 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: Plebeia frontalis is not expected to lower crop yield or lower crop value because there are already other insects present in California that may rob nectar and steal pieces of plants.  The bees are not expected to trigger the loss of any markets, change normal cultural practices, or interfere with the delivery or supply of water for agricultural uses.  There are parasites associated with stingless bees that are not known to be in California and can jump hosts when bees come into contact with either other or visit the same flowers5, possibly affecting honey bees or native pollinators.  These parasites and pathogens will be difficult to detect without destroying nesting cavities because they are less likely to be on healthy bees that are out foraging than on sick bees or in the brood comb.  frontalis may also be injurious to honey bees and native pollinators by competing for the same limited food supplies.  P. frontalis receives a Medium(2) rating 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: Plebeia frontalis is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  It is not expected to directly affected threatened or endangered species or disrupt critical habitats.  frontalis might trigger additional official or private treatment programs as some residents may consider their presence a nuisance.  P. frontalis is not expected to significantly impact cultural practices, home/urban gardening, or ornamental plantings.  P. frontalis receives a Medium(2) 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 Plebeia frontalis: Medium (11)

– Low = 5-8 points
– Medium = 9-12 points
– High = 13-15 points

6) Post Entry Distribution and Survey Information: Plebeia frontalis is known only from a single incursion into California, in Palo Alto. The bee 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:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (11)

Uncertainty:

There have been no surveys from Plebeia frontalis in California so it may have a much wider distribution than is presently realized.  There may be some economic benefits of having this species in California as the bees may be efficient pollinators of avocado2.  Furthermore, stingless bees were domesticated by the Mayans and dialogue in internet forums suggests that there may be a potential market for these bees in California as alternative pollinators.  The colony of stingless bees in Palo Alto may or may not have exotic parasites or pathogens.  P. frontalis and honey bees presumably coexist in Mexico and Central America and no new honey bee parasites or pathogens have been linked to this coexistence.

Conclusion and Rating Justification:

The establishment of Plebeia frontalis to California may have limited impact and a B-rating is therefore justified.  Economic impacts are expected to be limited to potential impacts on the pollination services of honey bees and native pollinators.  It is possible that P. frontalis could expose these pollinators to new exotic parasites or pathogens to which they are not adapted.  Furthermore, P. frontalis may compete with honey bees and native pollinators for limited food supplies.  P. frontalis may be a nuisance to some residents of California.  This could trigger the limited environmental impact of increased pesticide use in urban areas.

References:

1  Kennedy, C.M., E. Lonsdorf, M.C. Neel, N.M. Williams, T.H. Ricketts, R. Wilmfree, R. Bommarco, C. Brittain, A.L. Burley, D. Cariveau, L.G. Carvalhelro, N.P. Chacoff, S.A. Cunningham, B.N. Danforth, J. Dudenhoffer, E. Elle, H.R. Gaines, L.A. Garibaldi, C. Gratton, A. Holzschuh, R. Isaacs, S.K. Javorek, S. Jha, A.M. Klein, K. Krewenka, Y. Mandellk, M.M. Mayfield, L. Morandin, L.A. Neame, M. Otieno, M. Park, S.G. Potts, M. Rundolof, A. Saez, I. Steffan-Dewenter, H. Tald, B.F. Vlana, C. Westphal, J.K. Wilson, S.S. Greenleaf, and C. Kremen.  2013.  A global quantative synthesis of local and landscape effects on wild bee pollinators in agroecosystems.  Ecology Letters. http://labs.russell.wisc.edu/gratton/files/2013/03/Ecology-Letters.pdf

2Smith, R.H. and G. Ish-Am. 2006.  Stingless Bees Can Serve as Efficient Avocado Pollinators. http://www.avocadosource.com/papers/Research_Articles/GazitShmuel2006_POSTER.pdf

3 Cairns, C.E., R. Villanueva-Guiterriez, S. Kopter, and D.B. Bray.  2005.  Bee Populations, Forest Disturbance, and Africanization in Mexico.  Biotropica 37(4):686-692. http://www2.fiu.edu/~kopturs/pubs/CairnsetalBiotropica05.pdf

4J. M. F. Camargo & S. R. M. Pedro, 2013. Meliponini Lepeletier, 1836. In Moure, J. S., Urban, D. & Melo, G. A. R. (Orgs). Catalogue of Bees (Hymenoptera, Apoidea) in the Neotropical Region – online version. Available at http://www.moure.cria.org.br/catalogue. Accessed Sep/16/2013 http://moure.cria.org.br/catalogue?id=34972

5Allan H. Smith-Pardo, Ph.D.
Entomologist- Area Identifier
National Apoidea Specialist
USDA – APHIS – PPQ
389 Oyster Point Blvd. Suite 2
South San Francisco, CA. 94080

Responsible Party:

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

 Pest Rating: B

Posted by ls

Hymenoptera, Insects, Mites & Earthworms

Ochetellus glaber (Mayr): An Ant

California Pest Rating for
Ochetellus glaber (Mayr): An Ant
Hymenoptera: Formicidae
Pest Rating:  A
PEST RATING PROFILE
Initiating Event:

Ochetellus glaber is frequently intercepted by CDFA and presently has a temporary rating of “Q”.  A pest rating proposal is required to establish a permanent pest rating.

History & Status:

Background:  Ochetellus glaber is a species of ant that is adapted for living around the interface of open and scrub habitat1.  It often nests arboreally, under stones, or in dry fallen logs1.  The ants are generalist foragers that may feed on honeydew, insects, or worms.  They sometimes forage in houses for fluids or sweets but are not considered a major house pest1.  Colonies have multiple queens and colonies may reproduce by budding when a queen and some workers move to a new area.  This allows the ants to be transported long distances when nests or queens are moved as contaminating pests in commerce.

Worldwide Distribution: Ochetellus glaber is probably native to Australia.  It was first found in New Zealand in 19271 and Hawaii in 19772.  It has also invaded Japan and parts of Asia.  It recently spread to Florida3.

Official Control: Ochetellus glaber is not known to be under official control in any other states or nations4.

California Distribution:  Ochetellus glaber has never been found in the environment of California.

California Interceptions:  Between January 1, 2000 and December 31, 2014 Ochetellus glaber was intercepted 199 times by CDFA’s high risk programs and dog teams.  These interceptions have been on nursery stock and fresh plant parts from Hawaii.  The ant was also intercepted once at a border station on beehives from Florida.

The risk Ochetellus glaber would pose to California is evaluated below.

 Consequences of Introduction: 

1) Climate/Host Interaction: Ochetellus glaber is found in regions with similar climates to California. The ant can be expected to establish a widespread distribution in the state and receives a High (3) 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: Ochetellus glaber 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.  Ochetellus glaber 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: Ochetellus glaber is not expected to lower crop yields or increase crop production costs.  It is not expected to disrupt any markets for Californian agricultural commodities.  It is not expected to change cultural practices or vector other pestiferous organisms.  Ochetellus glaber is known to tend honeydew producing insects and may consume parasitoids, disrupting biological control of pests such as pink hibiscus mealybug5.  The ants are not expected to interfere with water supplies.  Ochetellus glaber receives a Low (1) 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 Ochetellus glaber 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 private treatment programs by residents who find infestations unacceptable and in the nursery industry.  Ochetellus glaber 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 Ochetellus glaber: 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: Ochetellus glaber has never been found 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)

Uncertainty:  

Invasive ants such as argentine ant (Linepithema humile) are already widespread in California and occupy many of the niches that Ochetellus glaber might be expected to colonize.  It is possible that competition from argentine ant may help preclude establishment of other invasive species such as Ochetellus glaber.  There is some evidence that Ochetellus glaber is a species complex and should be considered two or more distinct species6.

Conclusion and Rating Justification:

Ochetellus glaber has never been found in California and is expected to have limited economic and significant environmental impacts if it were to establish here.  An “A” rating is justified.

References:

1 Landcare Research Manaaki Whenua. Ochetellus glaber fact sheet.  http://www.landcareresearch.co.nz/publications/factsheets/Factsheets/ochetellus-glaber

2 Kirschenbaum, Ranit and J. Kenneth Grace. 2008. Agonistic Interactions Among Invasive Ant Species (Hymenoptera: Formicidae) from Two Habitats on Oahu, Hawaii.  Sociobiology 51(3): 543-553.  http://manoa.hawaii.edu/ctahr/termite/aboutcontact/grace/pdfs/241.pdf

3 Deyrup, M. 2003. An updated list of Florida ants (Hymeoptera: Formicidae). Florida Entomologist 86:43-48.  http://antkey.org/content/updated-list-florida-ants-hymenoptera-formicidae

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

5 González-Hernández, Héctor, Neil J. Reimer, and Marshall W. Johnson. 1999. Survey of the natural enemies of Dysmicoccus mealybugs on pineapple in Hawaii.  BioControl 44: 47-58.  http://link.springer.com/article/10.1023/A:1009954625169#page-2

6 Hoffman, Benjamin D., Alan N. Andersen, and Xiang Zhang. 2011. Taxonomic confusion of two tramp ant species: Iridomyrmex anceps and Ochetellus glaber are really species complexes. Current Zoology.  http://www.actazool.org/site_media/onlinefirst/downloadable_file/2011/06/30/11.1_incomplete_taxonomy_hinders_invasion_research.pdf

Responsible Party:

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

Pest Rating:  A

Posted by ls

Hymenoptera, Insects, Mites & Earthworms

Pheidole megacephala (Bigheaded Ant)

California Pest Rating for
Pheidole megacephala (Bigheaded Ant)
Hymenoptera: Formicidae
Pest Rating: A
PEST RATING PROFILE
Initiating Event:

On April 18, 2014, Dr. Rosser Garrison identified samples of ants collected at a residence in Costa Mesa, CA as Pheidole megacephala, bigheaded ant. The species is currently Q-rated, so a pest rating proposal is needed to determine future direction.

History & Status:

Background: Pheidole megacephala is a “tramp ant” invasive species that has spread around much of the tropical, subtropical, and temperate world where it is typically associated with the disturbed environments created by human habitations. Bigheaded ant primarily nests in soil and is often found nesting in disturbed soil, lawns, flowerbeds, under objects like bricks or cement slabs, flower pots, around trees and water pipes, and along the bases of structures and walkways2. Unlike other ants in the genus Pheidole, bigheaded ant is a major nuisance pest which frequently invades homes in search of food. Like subterranean termites, the ants sometimes build covered foraging tubes on building foundations or shrubs2. Bigheaded ants are omnivorous. Outdoors, they typically feed on honeydew, insects, seeds, and small vertebrates such as bird hatchlings. Indoors they are often found feeding on meat, pet food, oily foods such as peanut butter, and grease on stoves, counters, walls, or dish cloths3. Bigheaded ant invades homes so frequently in southern Florida that it is now considered to be the most common ant that triggers residents to call pest control companies2. Colonies of bigheaded ant have multiple queens and often form “supercolonies” where groups of queens and workers move off to expand the colony2. These large interconnected colonies make control of the ants difficult, as colonies can extend between and across properties. Other ant species are excluded from these areas. The most likely pathway for the long distance spread of bigheaded ant is when colonies in potted plants are moved1,2.

Worldwide Distribution: Pheidole megacephala is believed to be native to Africa1. From there it has spread to parts of Asia, Oceania, Central America, South America, Europe, Hawaii, and the Caribbean1. In the continental United States, bigheaded ant has been present in Florida since before 19332.

Official Control: Pheidole megacephala is listed as a quarantine pest by French Polynesia, Japan, and the Republic of Korea14.

California Distribution: In April 2014, Pheidole megacephala was found at a residential property in Costa Mesa. CDFA conducted a visual and SPAM-bait survey of a 5-mile radius around this site. At this time the ants were found to be confined within a 400m radius within the single residential neighborhood and an adjacent golf course. As of December, 2014, bigheaded ants have not been found in the environment of California outside of this neighborhood.

California Interceptions: Pheidole megacephala is commonly intercepted by CDFA. There have been 1,514 interceptions since January 1, 2000.

The risk Pheidole megacephala (bigheaded ant) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Pheidole megacephala tends to favor cool areas with high humidity3. The ants are likely to do well in coastal California and in irrigated areas elsewhere. Bigheaded ant 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: Pheidole megacephala is omnivorous and 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: Pheidole megacephala reproduces rapidly. Colonies have multiple queens and each queen lays up to 292 eggs each month2. Bigheaded ant spreads relatively slowly naturally, but colonies in potted plants can be transported long distances rapidly. Bigheaded ant 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: Pheidole megacephala is likely to injure agriculturally important animals when it tends honeydew producing insects in agricultural systems. The ants are known to tend economically important insects such as Asian citrus psyllid (ACP) (Diaphorina citri)9, green scale (Coccus viridis)4, grey pineapple mealybug (Dysmicoccus neobrevipes), and many others. While the ants are tending honeydew producers they consume predatory insects such as lady bugs and parasitic wasps including Tamarixia radiata9. This can disrupt the biological control component of existing IPM programs4 and allow honeydew producing pest insects to flourish, increasing crop damage and production costs. In southern Florida bigheaded ants are the primary ants that tend ACP9. In experiments they have been shown to greatly reduce the success of biological control with Tamarixia radiata9. For example, on Murraya paniculata bigheaded ants reduced the parasitism of ACP from 20.36% to 0.39%9. Furthermore, in their native range in Africa, bigheaded ants are known to use detritus and soil to build protective shelters over the psyllid Diaphorina enderleini10. These structures offer psyllids protection from environmental threats such as predators and contact insecticides. Bigheaded ants are listed as a quarantine pest by Japan, Korea, and French Polynesia14. The presence of these ants as hitchhikers on a wide variety of commodities may trigger disruptions to California exports. Bigheaded ants have also been documented chewing into drip irrigation systems, which may interfere with the delivery of water for agricultural uses5. Pheidole megacephala receives a High(3) in this category.

There may also be some positive economic impact from the entry of bigheaded ant to California. Bigheaded ants have been shown to help control pest insects in some circumstances by consuming damaging pest insects that do not produce honeydew and replacing them with less damaging honeydew-producing insects7. They also consume termites8.

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: Pheidole megacephala has the potential to cause massive, long-term alterations to natural communities and large-scale changes ecosystem processes. Although they are limited by the absence of water in dry areas, they can be expected to gradually invade most ecosystems and severely affect all native invertebrates. For example, they are well known to displace native ant fauna13. In an Australian rainforest, all insect larvae were found be absent from areas colonized by bigheaded ant12. Bigheaded ants can be expected to consume any threatened or endangered invertebrates that they encounter. The ants are also likely to facilitate the spread of noxious weeds through the environment by feeding on beneficial insects introduced for biological control6. Furthermore, bigheaded ant is also likely to trigger new treatments by residents as it invades homes in search of food and water. Many residents of Florida contact pest control companies to arrange chemical treatments due to infestations of homes by these ants2. Bigheaded ant 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 Pheidole megacephala (bigheaded 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: Pheidole megacephala is only known from a single incursion into a neighborhood in Costa Mesa. It 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 (14)

Uncertainty:

There is much uncertainty with the introduction of exotic ants to California. New species of ants may play a role in slow, long-term changes to our ecosystems that are difficult to observe on a short time scale. Alternatively, there are other species of ants already present in California and new species may have lesser effects. Argentine ant (Linepithema humile) occupies a similar niche to bigheaded ant and is already widely distributed in the state. It is possible that argentine ant may be able to outcompete bigheaded ant under some environmental conditions.

Bigheaded ant has not been observed building dirt shelters to protect ACP like it does closely related psyllids in its native range. However, most places where both ACP and bigheaded ant occur have frequent rainfall that may destroy any shelters. It is possible that the drier climate of California may be more favorable for this shelter-building behavior. If this occurs, it may complicate control of ACP by contact insecticides. If bigheaded ant were to both disrupt biological control of ACP by Tamarixia radiata and build shelters that protect ACP from contact insecticides, this may trigger additional management changes to organic citrus production in California.

Conclusion and Rating Justification:

Pheidole megacephala is likely to have significant economic impacts in California by disrupting biological control components of IPM programs and disrupting exports. This can be expected to increase production costs by triggering additional pest management. Bigheaded ant can also be expected to have significant long-term environmental impacts on the state and is under consideration for official control. An “A”-rating is justified.

References:

1CABI Invasive Species Compendium. http://www.cabi.org/isc/datasheet/40133

2Warner, John and Rudolph H. Scheffrahn. 2013. Featured creatures: big headed ant. http://entnemdept.ufl.edu/creatures/urban/ants/bigheaded_ant.htm

3Northern Territory Government. Big headed (or coastal brown) ant fact sheet. http://www.lrm.nt.gov.au/__data/assets/pdf_file/0018/11268/BigHAnt_Fact-Sheet.pdf

4Reimer, Neil J., Mei-li Cope, and George Yasuda. 1993. Interference of Pheidole megacephala (Hymenoptera: Formicidae) with biological control of Coccus viridis (Homoptera: Coccidae) in coffee. Environmental Entomology 22(2): 483-488. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Interference+of+Pheidole+megacephala&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=1

5Chang, Vincent C.S., Asher K. Ota, and Deborra Sanders. 1980. Parallel ridge barrier to control ant damage to orifices of drip irrigation tubes. Journal of Economic Entomology 73: 403-406. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Parallel+ridge+barrier+to+control&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=1

6Reimer, N.J. 1988. Predation on Liothrips urichi Karny (Thysanoptera: Phlaeothripidae): A case of biotic interference. Environmental Entomology 17(1): 132-134. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Predation+on+Liothrips+urichi&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=1

7Jones, Vincent P., Daphne M. Westcott, Naomi N. Finson, and Roy K. Nishimoto. 2001. Relationship between community structure and southern green stink bug (Heteroptera: Pentatomidae) damage in macadamia nuts. Environmental Entomology 30(6): 1028-1035. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Relationship+between+community+structure&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=4

8Cornelius, Mary L. and J.Kenneth Grace. 1996. Effect of two ant species (Hymeoptera: Formicidae) on the foraging and survival of the Formosan subterranean termite (Isoptera: Rhinotermitidae). Environmental Entomology 25(1): 85-89. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Effect+of+two+ant+species&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=4

9Navarrete, Bernardo, Heather McAuslane , Mark Deyrup and Jorge E. Peña. 2013. Ants (Hymenoptera: Formicidae) Associated with Diaphorina citri (Hemiptera: Liviidae) and their Role in its Biological Control. Florida Entomologist, 96(2):590-597. http://swfrec.ifas.ufl.edu/hlb/database/pdf/21_Navarrete_13.pdf

10Alene, Desiree Chantal, Champlain Djieto-Lordon, and Daniel Burckhardt. 2011. Unusual behavior—unusual morphology: mutualistic relationships between ants (Hymenoptera: Formicidae) and Diaphorina enderleini (Hemiptera: Psylloidea), associated with Vernonia amygdalina (Asteraceae). African Invertebrates 52(2):353-361. http://www.bioone.org/doi/abs/10.5733/afin.052.0210?journalCode=afin

11Jahn, Gary C. and John W. Beardsley. 1996. Effects of Pheidole megacephala (Hymenoptera: Formicidae) on survival and dispersal of Dysmicoccus neobrevipes (Homoptera: Pseudococcidae). Journal of Economic Entomology 89(5): 1124-1129. http://esa.publisher.ingentaconnect.com/search/article?option1=tka&value1=Effects+of+Pheidole+megacephala+%28+Hymenoptera%3a+Formicidae+%29+on+survival+and+dispersal+of+Dysmicoccus+neobrevipes&operator9=AND&option9=publications&value9=esa&sortDescending=true&sortField=default&pageSize=10&index=1

12Hoffmann, Benjamin D., Alan N. Andersen, and Greg J.E. Hill. 1999. Impact of an introduced ant on native rainforest invertebrates: Pheidole megacephala in monsoonal Australia. Oecologia 120: 595-604. http://www.issg.org/database/species/reference_files/phemeg/hoffmann1999.pdf

13Vanderwoude, C., L.A. Lobry De Bruyn, and A.P.N. House. 2001. Response of an open-forest ant community to invasion by the introduced ant, Pheidole megacephala. Austral Ecology 25(3): 253-259. http://onlinelibrary.wiley.com/doi/10.1046/j.1442-9993.2000.01021.x/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false

14USDA 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.

 Pest Rating: A

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