Eumerus figurans | Pest Rating Proposals and Final Ratings

California Pest Rating for

Eumerus figurans (Walker): Ginger Maggot

Diptera: Syrphidae

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

Eumerus figurans is occasionally intercepted by CDFA’s high risk programs and is presently assigned a temporary rating of “Q”. A pest rating proposal is required to assign a permanent pest rating.

History & Status:

Background: Eumerus figurans is a syrphid fly whose larvae feed on various bulbs, corm, and roots¹. Female flies are attracted to and lay eggs on injured and rotting bulbs, corms and roots^1,2. Larvae are gregarious and hollow out bulbs as they feed². Damage by the larvae is considered secondary to bacterial and fungal rot organisms¹. Known hosts include ginger roots, lily bulbs, narcissus bulbs, decomposing pineapple stumps, and rotting dry land taro¹. Larvae of Eumerus figurans may be transported long distances when infested ginger roots or other plant parts are moved.

Worldwide Distribution: The native range of Eumerus figurans is probably the tropical forests of South-east Asia. Walker described the species from Celebes and there are undescribed sibling species present in Thailand, suggesting an evolutionary origin in that region. Eumerus figurans has spread throughout much of Asia and the Southwest Pacific¹. It was first found in Hawaii in 1902¹.

Official Control: Eumerus figurans itself is not known to be under official control by any other states or nations³. However, all members of the genus Eumerus are considered harmful organisms by Bermuda³, Iceland³, and Japan³.

California Distribution: Eumerus figurans has never been found in the environment of California.

California Interceptions: Between January 1, 2000 and December 31, 2014 Eumerus figurans was intercepted 20 times by CDFA’s high risk programs. All interceptions for which data were recorded were on shipments of ginger root from Hawaii.

The risk Eumerus figurans (ginger maggot) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Ginger grows as a perennial plant in USDA zones 9 through 12. This corresponds with much of California. Eumerus figurans is likely capable of finding injured ginger roots to feed on throughout this area. However, the fly is typically found in humid tropical and subtropical environments. Ginger maggot 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: Eumerus figurans is known to feed on injured ginger roots, lily bulbs, narcissus bulbs, decomposing pineapple stumps, and rotting dry land taro1. It receives a Low (1) 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: Species of Eumerus are thought to have 3 generations per year in Israel³. Since California also has a Mediterranean climate Eumerus figurans is likely to have 3 generations per year here. Female flies lay eggs in groups of 10-20 per bulb³, giving them a high reproductive rate. The flies may be transported long distance through the movement of infested plants or plant parts. Eumerus figurans 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: Eumerus figurans is considered a secondary pest of ginger and there appears to be more literature published on the fly’s role as a pollinator than a pest. It is not expected to lower any crop yields in California. Ginger maggot is likely to be considered a quarantine pest by Iceland³, Bermuda³, and Japan³ and has the potential to disrupt exports of ginger, lily, or narcissus bulbs to those markets. However, Eumerus figurans is unlikely to establish in Iceland and is already present on Nansei Island in Japan. Lost markets may therefore be limited to exports of ginger, lily, and narcissus bulbs to Bermuda. The fly may also increase crop production costs if growers manage populations of the flies. Eumerus figurans is not expected to negatively change normal cultural practices, vector pestiferous organisms, injure animals, or interfere with water supplies. It receives a Medium (2) 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: If Eumerus figurans were to enter California it is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. Ginger maggot is not expected to directly affect threatened or endangered species or disrupt critical habitats. It is possible that the flies could trigger new treatment programs in the nursery industry, ginger gardens, or by residents who consider flies a nuisance. Ginger maggot is not expected to significantly impact cultural practices, home/urban gardening, or ornamental plantings. Eumerus figurans 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 Eumerus figurans (Ginger Maggot): Medium (10)

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: Eumerus figurans has never been found in the environment 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: Medium (10)

Uncertainty:

There is some speculation that Eumerus figurans might play a role in the spread of bacterial and fungal rot organisms between ginger plants¹. If confirmed, this could increase its economic impact.

Conclusion and Rating Justification:

Eumerus figurans (ginger maggot) has never been found in California. It is expected to have limited economic and environmental impacts if it were to enter the state. A “B” rating is justified.

References:

¹ Mau, R.F.L., J.L. Martin Kessing. 1992. Eumerus figurans (Walker). Hawaii Crop Knowledge Master. http://www.extento.hawaii.edu/kbase/crop/type/eumerus.htm

² Hill, Dennis S. 1987. Agricultural Insect Pests of Temperate Regions and Their Control. CUP Archive. 659pp. https://books.google.com/books?id=3-w8AAAAIAAJ&dq=eumerus+figurans+ginger&source=gbs_navlinks_s

³ USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). https://pcit.aphis.usda.gov/pcit/