Leek Moth | Acrolepiopsis assectella (Zeller)

California Pest Rating for 
Leek Moth | Acrolepiopsis assectella (Zeller)
Lepidoptera: Acrolepiidae
Pest Rating: A



Initiating Event:

On July 3, 2018 USDA released a New Pest Advisory Group (NPAG) report proposing to change the status of Acrolepiopsis assectella (leek moth) to non-actionable within the continental United States.  A pest rating proposal is required to determine future direction.

History & Status:

Background:  Leek moth is a leaf-mining moth that feeds on plants in the genus Allium1. Preferred hosts of the moth are garlic, leek, and onion1. Over-wintering adults become active when temperatures reach 15ºC1.  Female moths lay eggs on leaves which larvae mine1.  Mature larvae emerge from the leaf tissue and pupate on the external surface of the plant1.  When adults emerge they either begin another generation or overwinter1, depending on the time of year.  Leek moth can rapidly spread long distances when infested plant material is moved.

Worldwide Distribution: Leek moth is presumably native to Eurasia. It was first found in North America in Ontario in 19931.  Leek moth was first detected in the United States in New York in 2009 and has since spread to New Hampshire, Maine, and Vermont1.

Official Control: Leek moth is listed as a harmful organism by Chile, Colombia, Costa Rica, Ecuador, French Polynesia, Honduras, Israel, Japan, the Republic of Korea, Mexico, New Caledonia, Nicaragua, Peru, and Taiwan3.

California Distribution:  Leek moth has not been found in the environment of California.

California Interceptions:  Leek moth has never been intercepted in California.

The risk Acrolepiopsis assectella (leek moth) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Leek moth is expected to be able to establish a widespread distribution in California wherever Allium plants grow. Based on its current widespread distribution in Europe and northern Africa it is not expected to be limited by climate in California.  It 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: Leek moth is only known to feed on plants in the genus Allium.  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: Leek moth has a high reproductive rate with each female laying an average of 100 eggs and the population completing as many as 8 generations per year1, depending on climate.  The moth can rapidly spread long distances when eggs, larvae, or pupae on plants or harvested plant parts are moved.  Adults can also fly.  Leek moth 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: California is the largest producing state in the U.S. of garlic, onions, and green onions.  The state produces 90%+ of the commercial garlic, is the largest producer of processing onions, and is one of the top fresh market onion producers in the nation2.  Both garlic and onion crops are valued at $150-$300 million each annually2.  California also leads the nation in the production of green onions with a 2009 crop value of $28 million in Monterey and Riverside county alone4.  If leek moth were to establish in California it is expected to lower crop yields and increase production costs of these crops, especially on organic farms.  Leek moth causes damage of economic importance in Allium  Yield reductions can be as high as 50 percent and have the potential to reach 100 percent for organic growers who do not implement sufficient control measures1.  Its presence in the state would likely affect markets for fresh garlic and onions.  Growers in other places infested with leek moth have changed cultural practices including crop row netting, crop rotation, delayed planting, removal of old and infested leaves, destruction of pupae or larvae, early harvesting, avoidance of planting crops near known infestations, and destruction of plant debris following harvesting1.  The moth is not expected to vector other organisms, injure animals, or interfere with water supplies.  Leek moth receives a High (3) in this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D

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.

Economic Impact Score: 3

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 leek moth were to establish in California it is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  It is likely to affect threatened and endangered species such as Munz’s onion (Allium munzii) and Yosemite onion (Allium yosemitense).  Leek moth would not be expected to disrupt critical habitats.  It is likely to trigger additional treatment programs in agriculture and in residential gardens.  Species of Allium are grown in home/urban gardens and would be significantly affected by this pest.  Leek moth receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Economic Impact: B, D, E

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.

Environmental Impact Score: 3

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 Acrolepiopsis assectella (leek moth):  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: Leek moth 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)


Leek moth causes significant damage to plants in the genus Allium.  Its presence in California would rapidly come to the attention of garlic and onion growers, so there is little uncertainty regarding its absence from the state.  There is low uncertainty with this pest.

Conclusion and Rating Justification:

If leek moth were to become established in California it would have significant economic and environmental impacts.  An “A” rating is justified.


1 USDA New Pest Advisory Group:  NPAG Report Acrolepiopsis assectella (Zeller): Leek moth.  June 29, 2018.

2 California Garlic & Onion Research Advisory Board.  http://www.cagarlicandonion.com/

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

4 Smith, Richard, Michael Cahn, Marita Cantwell, Steven Koike, Eric Natwick, and Etaferahu Takele. 2011.  Green Onion Production in California.  UC Vegetable Research & Information Center Vegetable Production Series.  http://anrcatalog.ucanr.edu/pdf/7243.pdf


Jason Leathers, 1220 ‘N’ Street, Sacramento CA 95814, (916) 654-0312, plant.health[@]cdfa.ca.gov

Responsible Party:

Kyle Beucke, 1220 N Street, Room 221, Sacramento, CA, 95814, 916-403-6741, plant.health[@]cdfa.ca.gov

Comment Period:* CLOSED

9/24/18 – 11/8/18


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Pest Rating: A


Posted by ls