Plebeia frontalis | Pest Rating Proposals and Final Ratings

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