Enarmonia formosana (Scopoli) | Cherry Bark Tortrix

California Pest Rating for
Enarmonia formosana (Scopoli):  Cherry Bark Tortrix
Lepidoptera:  Tortricidae
Pest Rating:  A

Initiating Event:

Enarmonia formosana (cherry bark tortrix) is established in the Pacific Northwest, where it is a significant pest of cherry and other Prunus species.  CDFA’s stone fruit commodity-based survey includes trapping for this moth, which is currently unrated.  A pest rating proposal is needed before cherry bark tortrix is detected in California.

History & Status:

Background:  Enarmonia formosana is a wood boring moth whose larvae feed on the bark and sapwood of practically all rosaceous trees, including Prunus (cherry, almond, apricot, nectarine, peach, and plum), Cydonia (quince), Malus (apple), Pyrus (pear), Sorbus (mountain ash), and Pyracantha (firethorne)1.  There is one generation per year2.  Adult moths fly and lay eggs from April to September2.  Eggs are laid in cracks, crevices, wounds, crotches, and lenticels of trees2.  Eggs hatch after a few weeks and larvae seek out openings in the bark through which they enter the tree2.  Larvae burrow deep into the cambium where they feed until the following spring2.  Feeding causes dieback and wilting of the tree canopy and the damage makes the tree susceptible to bacterial and fungal diseases, frost damage, and other insect pests2.  This secondary damage can be fatal to the tree.  Because the moths usually attack mature trees, the most likely pathway for spread of cherry bark tortrix into California is through firewood of the host species.

Worldwide Distribution: Enarmonia formosana is native to the Palearctic region.  It is widespread in Europe, temperate Asia, and North Africa1.  The first North American detection was in Richmond, British Colombia in May, 19891.  From there, it has been spreading to the south.  It was found just across the border in Whatcom county, Washington in 19912 and then in Oregon in 20004.  Although the moth is widespread in western Washington, it has not been found in eastern Washington, suggesting that the Cascades may be a barrier to natural spread of the moth.

Official Control: Oregon has established a quarantine against Enarmonia formosana regulating the entire state of Washington, the entire province of British Colombia, Multnomah and Clackamas counties in Oregon, and any other state, province, or territory where an established population of the moth is detected and not eradicated.  The quarantine covers all plants in the genera Crataegus, Cydonia, Malus, Prunus, Pyracantha, Pyrus and Sorbus, and unseasoned firewood derived from trees of these host plant genera.  Uninfested nursery stock plants of these genera that are less than two inches in diameter are exempted from the quarantine3.

California Distribution Enarmonia formosana has never been detected in California.  Trapping for the moth is included in CDFA’s stone fruit commodity-based survey and it has not been trapped, further supporting its absence from the State.

California Interceptions Enarmonia formosana has never been intercepted in any regulatory situations in California.

The risk cherry bark tortrix (Enarmonia formosana) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Rosaceous plants are widely cultivated in California and Enarmonia formosana is likely to establish wherever they are grown. Cherry bark tortrix 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: Although cherry bark tortrix is only reported to feed on plants in one family (Rosaceae), these hosts include economically important fruit crops valued at billions of dollars annually.  Enarmonia formosana receives a High(3) 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: Cherry bark tortrix spread rapidly throughout western Washington in a decade, infesting 80% of host trees in some areas.  This indicates high reproductive and local dispersal potential.  The moths can spread long distances through the movement of infested firewood or large plants.  Enarmonia formosana 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: Enarmonia formosana is likely to lower the yield of infested host trees.  Crop production costs can be expected to increase if cherry bark tortrix establishes in California as growers are likely to use insecticides, mating disruption, or biological control agents to control moth populations.   The presence of the moth in the State may also trigger lost markets for large nursery stock plants and host firewood.  Cherry bark tortrix 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

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: Enarmonia formosana is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes.  It is not expected to directly affect any threatened or endangered species or disrupt critical habitats.  The moth can be expected to trigger additional official or private treatment programs.  A survey found that 75-80% of host trees were infested with cherry bark tortrix in the Bellingham, WA area.  This indicates that the pest can be expected to significantly impact home/urban gardening and ornamental plantings.  Enarmonia formosana receives a High(3) in this category.

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

Environmental Impact: 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. 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 Enarmonia formosana (cherry bark tortrix):  High(15)

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: Enarmonia formosana has never been detected 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(15)


There is a report that high temperatures above 90˚F might be lethal to eggs5.  High temperatures could therefore limit populations of the moth in some areas of the state.  It is also possible that existing IPM programs might manage cherry bark tortrix populations in some circumstances.

Conclusion and Rating Justification:

Enarmonia formosana is present in the Pacific Northwest where it is a significant pest of rosaceous trees.  From Canada, the moth rapidly spread south through western Washington.  However, a quarantine in Oregon has effectively slowed its spread.  Nevertheless, cherry bark tortrix is likely to spread to California in the future, most likely in infested firewood.  When it arrives it is expected to have significant economic and environmental impacts in the state and may trigger official treatments.  An “A” rating is justified.


1Dang, P.T. and D.J. Parker.  1990.  First records of Enarmonia formosana (Scopoli) in North America (Lepidoptera: Tortricidae).  Journal of the Entomological Society of British Colombia.  87:3-6. https://journal.entsocbc.ca/index.php/journal/article/view/655

2Murray, Todd.  Garden Friends & Foes:  Cherry Bark Tortrix.  Washington State University.  http://whatcom.wsu.edu/ag/homehort/pest/e_formosana.htm


3Oregon Department of Agriculture Plant Programs:  Cherry Bark Tortrix.  http://arcweb.sos.state.or.us/pages/rules/oars_600/oar_603/603_052.html

4Cherry bark tortrix moths found in Oregon.  The Seattle Times.  August 7, 2000.  http://community.seattletimes.nwsource.com/archive/?date=20000807&slug=4035429

5Westcott, R.L. and J.D. DeAngelis.  1993.  New Pest Alert:  Cherry Bark Tortrix Moth.  Oregon State University Extension Service and Oregon Department of Agriculture.   http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/19518/ec1409-e.pdf

Responsible Party:

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

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Pest Rating:  A

Posted by ls