Tag Archives: Ophiomyia kwansonis

Ophiomyia kwansonis Sasakawa: Daylily Leafminer

California Pest Rating for
Ophiomyia kwansonis Sasakawa: Daylily Leafminer
Diptera: Agromyzidae
Pest Rating:  B

Initiating Event:

June 23, 2015 Dr. Martin Hauser tentatively identified an intercepted insect as Ophiomyia kwansonis.  This is the first time this insect has been intercepted by CDFA and a pest rating proposal is required to determine future direction on this insect.

History & Status:

BackgroundOphiomyia kwansonis is a leafmining fly that feeds on the leaves of daylilies (Hemerocallis spp.)1,2.  Adult female flies typically lay eggs near the tip of the leaf blade1.  As larvae feed they create mines that appear as long, prominent, whitish lines1.  Larvae pupate in mines, often near the leaf base1.  Mining does not kill plants1.  Daylily leafminer may be transported long distances when infested daylilies are moved.

Worldwide Distribution: Ophiomyia kwansonis is native to Japan and Taiwan2.  In March 2011 it was first found in the United States in a nursery in Florida1 and by 2014 had been found in Alabama, Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Mississippi, Missouri, New Hampshire, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and West Virginia2.  It has also spread to Europe1.

Official Control: Ophiomyia kwansonis is not listed as a harmful organism by any states or nations3 and is not known to be under official control in any locations.

California Distribution: No official samples of Ophiomyia kwansonis have ever been collected in California.  However, there is a published report of a photograph from Irvine (Orange County) that shows a plant that has likely been damaged by the fly4.

California Interceptions Ophiomyia kwansonis has only been intercepted once by CDFA on a shipment of daylilies (Hemerocalis sp.) from Delaware to Contra Costa County (PDR 070P06223714).

The risk Ophiomyia kwansonis (daylily leafminer) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Ophiomyia kwansonis is widespread in the eastern United States and it is expected to be able to establish anywhere that daylilies are grown. Daylily leafminer 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: Ophiomyia kwansonis is only known to feed on daylilies (Hemerocallis) and 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: Ophiomyia kwansonis has a high reproductive potential.  It can complete 2-3 generations per year in cooler climates and breed continuously under warm conditions1,2.  The leafminer may disperse locally by flying and may be transported long distances as eggs, larvae, or pupae on infested daylilies.  Daylily leafminer 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: If Ophiomyia kwansonis were to become established in California it is not expected to lower crop yields.  It is likely to lower the value of daylily nursery stock by disfiguring plants with its presence.  The leafminer is not expected to disrupt any markets, change cultural practices, vector other organisms, injure animals, or interfere with water supplies.  Daylily leafminer 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: If daylily leafminer were to become established in California it is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  It is not likely to directly affect threatened or endangered species or disrupt critical habitats.  In Florida growers are advised to remove and destroy obviously mined leaves1.  No new chemical treatment programs are expected.  Daylily leafminer is expected to significantly impact daylilies which are common ornamental plants.  Ophiomyia kwansonis 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 Ophiomyia kwansonis (Daylily Leafminer):  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: Daylily leafminer has not been found in the environment of 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)


Eggs and young larvae of daylily leafminer are very difficult to detect in visual inspections.  Given the wide distribution of the fly in the eastern United States and rapidity of its spread it is possible some of the flies may have already entered California.

Conclusion and Rating Justification:

Ophiomyia kwansonis has not been found in California and is expected to have significant impacts on the nursery industry and ornamental plantings if it becomes established in the state.  A “B” rating is justified.


1 Steck, Gary J. and Gaye L. Williams. 2013. Daylily Leafminer, Ophiomyia kwansonis Sasakawa (Diptera: Agromyzidae), new to North America, including Florida.  Pest Alert. Florida Department of Agriculture and Consumer Services, Division of Plant Industry.  DACS-P-01807. http://freshfromflorida.s3.amazonaws.com/ophiomyia-kwansonis.pdf

2 Bethke, James A. 2014. Insect Hot Topics: Daylily leafminers. UCNFA News. http://ucanr.edu/sites/UCNFAnews/Insect_Hot_Topics/Daylily_leafminers/

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

4 Williams, Gaye L. and Gary J. Steck. 2014.  Ophiomyia kwansonis Sasakawa (Diptera: Agromyzidae), the Daylily Leafminer, an Asian Species Recently Identified in the Continental United States.  Proceedings of the Entomological Society of Washington 116(4): 421-428.

Responsible Party:

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

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating:  B

Posted by ls