Azalea Leafminer | Caloptilia azaleella (Brants)

California Pest Rating for
Caloptilia azaleella (Brants):  Azalea leafminer
Lepidopetera:  Gracillariidae
Pest Rating: C



Initiating Event:

Gracillariidae insects were recently intercepted by CDFA through high risk pest exclusion program on a shipment of azalea plants, originating from Kentucky. The most common Gracillariidae, intercepted on Azalea is Caloptilia azaleella. This insect has been previously rated C by CDFA. A pest rating proposal is required to evaluate the current rating for this species.

History & Status:

BackgroundCaloptilia azaleella are small, yellow moths with purplish markings on the wings. Leaf mining stage is a yellowish caterpillar about half inch long. Caloptilia azaleella is known to attack only azaleas (Rhododendron spp.) worldwide. The larvae mine the leaf tissue; as these mines age, they cause brown blisters on the leaves. The mature larvae emerge from leaf tissue, then roll and tie the edge of the leaves around themselves for protection. They can cause considerable damage to greenhouse grown azaleas in North Carolina (Frank, 2016). Maximum infestation in Florida nurseries was noted from early spring through summer (Dekle, 2007). In Oregon, where it has been  introduced, there are three generations per year.

Worldwide Distribution:

Caloptilia azaleella is endemic to Japan but has been introduced to all azalea growing parts of the world including Europe (southern Britain), New Zealand and eastern Australia (T.E.R.R.A.I.N, 2018).

In the North America, it has been found in the Unites States and Canada from Florida to Texas, Long Island, West Virginia and Ohio, California, Washington and British Colombia (Johnson and Lyon, 1994).

Official Control: Caloptilia azaleella has been listed as harmful organism in Chile (USDA -PCIT).

California DistributionCaloptilia azaleella was introduced to California in 1962 for the first time (Essig Museum Online Database, 2010) and more recently observed in Sonoma county (2017) and Shasta county (2014) (iNaturalist, 2016).

California InterceptionsCaloptilia azaleella has been intercepted through high risk pest exclusion and interior quarantine programs in California (Pest and Damage Report Database, 2018).

The risk Caloptilia azaleella ( azalea leaf miner) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Rhododendron spp. grow best in filtered shade and prefer acidic soils with high organic content and excellent drainage (Pests in garden and Landscapes, 2017). This type of climate is found in northern California and extends down the coast to San Francisco Bay (American Rhododendron Society, 2018). Some of the maddenii-type rhododendron can grow in southern California as well. Since C. azaleella is already introduced and present in Northern CA, its introduction and spread to the rest of the state is likely. It receives a Medium (2) in this category.

Score: 2

– 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: Caloptilia azaleella feeds only on Rhododendron spp. It receives a Low (1) in this category

Evaluate the host range of the pest:

Score: 1

– 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: Caloptilia azaleella deposits 1-5 eggs on the undersurface of leaves during spring time. The life cycle is completed in one week. It overwinters as a last instar larva or pupa in a rolled leaf. Larva can be found on leaves all year around. There are three generations in western states and three to four generations in southern states. Because azaleella does not leave its host during the entire life cycle, it does not spread over large distances. However, movement of infected azalea nursery stock could likely disperse this species. It receives a Medium (2) in this category.

Evaluate the natural and artificial dispersal potential of the pest:

Score: 2

– 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: Caloptilia azaleella is a pest of container and field grown nursery stock but can also attack landscape grown plants. Heavy infestation may not kill the plant, especially if it can be controlled during early stages of growth but the damage is likely to affect the appearance and quality of the plant. Increased cost of pruning of infested branches and release of parasitoids can add to production costs and decrease the value of the crop (Dekle, 2007). It receives a Medium (2) in this category.

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

Economic Impact: A, B, 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.

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: Caloptilia azaleella is not likely to lower biodiversity and disrupt any natural habitats. It has also not been reported to affect any endangered species, either directly or indirectly. It could attack native rhododendron and native azaleas but unlikely to cause significant damage. The infestations of azaleas would likely trigger chemical treatments by homeowners. It receives a Medium (2) in this category.

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

Environmental Impact: D

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: 2

– 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 Caloptilia azaleella (azalea leaf miner): 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: Caloptilia azaleella (azalea leafminer) has been found in the environment and receives a Low (-1) 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:

Score: -1

-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 (9)


Caloptilia azaleella is present in azalea growing areas in Northern California and has also been detected by CDFA from time to time. However, it is not widespread in the state, possibly due to its inability to attack any other host plants. There are some varieties of Rhododendron, being grown in Southern CA and it may be present in large azalea growing areas than is currently known

Conclusion and Rating Justification:

Caloptilia azaleella has been reported in the environment of California. However, it is not likely to have significant economic and environmental impacts. A “C” rating is justified.


 American Rhododendron Society (ARS): California Chapter, 2018. Plant Culture and Care. P.O. Box 214, Great River, NY 11739. Accessed 6/14/2018:

Dekle, G.W. 2007. Azalea Leaf miner: Featured Creatures. Entomology and Plant Pathology. Publication # EENY-379, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, University of Florida. Accessed 6/14/2018:

Essig Museum Online Database, 2010. California Moth Specimen Database. University of California, Berkeley. Accessed 6/21/2018

Frank, S. 2016. Azalea leafminer. Entomology Insect Notes. North Carolina State Extension Publications North Carolina State Extension. Accessed 6/14/2018:

iNaturalist, 2016. Online crowdsourced species identification system and an organism occurrence recording tool. Gracillariidae of California. Caloptilia azaleella

Johnson WT and Lyon HH. 1994. Insects That Feed on Trees and Shrubs. 2nd ed. rev. Cornell University Press, Ithaca, NY.

Pest and Damage Report Database, 2018. Caloptilia azaleella. Plant Health and Pest Prevention Services. California Department of Food and Agriculture. Accessed 6/14/2018:

Pests in gardens and landscapes, 2017. Azalea-Rhododendron spp. Agriculture and Natural Resources, University of California. Statewide Integrated Pest Management Program. Accessed 6/15/2018:

Reding, Tom. 2018. Caliptilia azaleella. Wikipedia- the free encyclopedia. Accessed 6/19/2018:

Richers, K. 1996. California Moth Specimens Database. Caloptilia azaleella. University of California, Berkeley. Accessed 6/21/018.

Taranaki Educational Resource: Research, Analysis and Information Network. (T.E.R.R.A.I.N.), 2018. “Caloptilia azaleella (Azalea leafminer moth)”. The MAIN trust GIS community project. Government of New Zealand. Accessed 6/14/2018:

USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). Harmful organism report: Caloptilia azaleella. Accessed 6/14/2018.


Raj Randhawa, 1220 ‘N’ Street, Room 221, Sacramento CA 95814, (916) 403-6617, plant. health[@]

Responsible Party:

Jason Leathers, 2800 Gateway Oaks, Sacramento CA 95833, (916) 654-1211,[@]

Comment Period:* CLOSED

7/30/18 – 9/13/18


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Pest Rating: C


Posted by ls