Operophtera brumata (L.) | Winter Moth

California Pest Rating for
Operophtera brumata (L.):  Winter Moth
Lepidoptera:  Geometridae
Pest Rating:  A

Initiating Event:

In January 2013 USDA announced that Operophtera brumata, winter moth, was under consideration for deregulation at our ports.  Stephen Brown (CDFA) recommended a rating proposal for the moth.

History & Status:

Background:  Winter moth is an invasive, polyphagous moth that feeds on flower and leaf buds and expanding leaf clusters of more than 160 species of trees and shrubs from 14 plant families3.  In Oregon, adult moths emerge from pupae in soil from early November through December1.  Females are unable to fly.  They climb trees, mate, and lay eggs in bark crevice.  Eggs hatch mid-March. First (1st) instar larvae may balloon by wind; closely related species have been documented dispersing 850m2.  By May larvae have completed development.  They then drop from trees and pupate 1-12 cm below the soil surface3.

Worldwide Distribution: Operophtera brumata is native to Palearctic region.  It was first detected in North America in Nova Scotia in 1949, but is believed to have been introduced before 19351.  It was found in British Columbia in 1976 and Oregon in 1978.  However, museum specimens from a natural history museum indicate that the moth was present in Oregon in 1958, but misidentified as the native moth Operophtera occidentalis.  Recently, winter moth has invaded Maine, New Hampshire, Massachusetts, Rhode Island, and New York (Long Island).4

Official Control: United States Department of Agriculture has listed Operophtera brumata as an actionable pest.  It is unknown if winter moth is under official control anywhere else.

California Distribution:  Operophtera brumata has never been found in California.

California Interceptions Operophtera brumata has never been intercepted in California.

This risk winter moth would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Operophtera brumata is highly polyphagous and can be expected to find a plethora of suitable hosts in California. Temperatures above 27˚C (80.6˚F) are reportedly lethal to eggs6; therefore, winter moth may not be able to establish in portions of southern California where temperatures are warm between January and March.  Winter moth is expected to establish a widespread distribution in the cooler parts of California.  Winter moth 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) Pest Host Range: Operophtera brumata feeds on more than 160 species of trees and shrubs from 14 plant families.  The moth 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: While adult winter moths have limited natural dispersal capabilities given their flightless females, wind-aided larval dispersal by ballooning is a valid concern.  Furthermore, the moth may be moved long distances through trade in nursery stock.  Female winter moths lay 150-350 eggs.  Operophtera brumata receives a Medium(2) 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: Winter moth is considered a major pest of blueberries (an $82 million industry in California) and deciduous trees in Washington.  Hosts also include a number of other economically important crops, including almond5 ($3.9 billion), raspberries ($223 million), cherry5,7 ($197 million), pears ($98 million), and apple ($58 million).  Operophtera brumata has the potential to impact crops by consuming flower buds and defoliating trees, reducing crop yield.  The moth may also trigger additional treatment programs during prebloom and bloom stages, increasing crop production costs.  Chemical treatments during bloom have the potential to disrupt pollination services, negatively changing normal cultural practices.  The moth is therefore expected to have a significant economic impact on California.  Winter moth receives a High(3) rating in this category.

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

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.

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:  As Operophtera brumata invades new areas, it can cause widespread defoliation4.  Forest trees can be defoliated and forced to grow a second set of flush.  When combined with other stressors, such as drought, this can kill trees.  Rosa is listed as a host of winter moth and small-leaved rose (Rosa minutifolia) is listed as an endangered species by the state of California.  However, winter moth is not expected to establish in warmer parts of the state where small-leaved rose is found.  Winter moth may also impact home/urban gardening and ornamental plantings by defoliating trees, reducing fruit yields, or triggering additional treatments by residents.  O. brumata receives a High(3) rating in this category.

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

Environmental Impact:  A, 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 Winter Moth:  High (14)

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: Operophtera brumata has never been collected in California.  Winter moth therefore receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and backed up 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 ecoarea (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous ecoareas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous ecoareas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score:  High (14)


The parasitoids Cyzenis albican (Diptera: Tachinidae) and Agrypon flaveolatum (Hymenoptera: Ichneumonidae) have been introduced to the United States and Canada as biological control agents to control winter moth populations.  In most areas they have been successful at limiting damage from the moth.  However, winter moth populations sometimes continue to reach outbreak levels after parasitoids are introduced3.  It is not certain if the parasitoids would be successful in California, or if resources would be available for mass-rearing programs.  It is also uncertain if O. brumata populations would be controlled by existing IPM programs in some agricultural ecosystems, mitigating economic damage.  Also, since there have been no recent surveys, it is possible that winter moth might be established in limited areas of the state and unnoticed.

Conclusion and Rating Justification:

Winter moth (Operophtera brumata) has potential to cause significant economic and environmental damage to California.  An ‘A’ rating is justified.


1Kimberling, D.N., J.C. Miller, and R.L. Penrose.  1986.  Distribution and parasitism of winter moth, Operophtera brumata (Lepitoptera: Geometridae), in western Oregon.  Environmental Entomology 15: 1042-1046.

2Brown, C.E.  1962.  The life history and dispersal of the bruce spanworm, Operophtera bruceata (Hulst.), Lepidoptera: Geometridae.  Can. Ent. 94:1103-1107.

3Horgan, F.G., J.H. Myers, and R. Van Meel. 1999.  Cyzenis albicans (Diptera: Tachinidae) does not prevent the outbreak of winter moth (Lepidoptera: Geometridae) in birch stands and blueberry plots on the lower mainland of British Columbia.  Environ. Entomol. 28(1): 96-107.  https://academic.oup.com/ee/article-abstract/28/1/96/502294/Cyzenis-albicans-Diptera-Tachinidae-Does-Not?redirectedFrom=PDF

4Elkinton, J.S., G.H. Boettner, M. Sremac, R. Cwiazdowski, R.R. Hunkins, J. Callahan, S.B. Schuefele, C.P. Donahue, A.H. Porter, A. Khrimian, B.M. Whited, and N.K. Campbell.  2010.  Survey for winter moth (Lepidoptera: Geometridae) in northeastern North America with pheromone-baited traps and hybridization with the native bruce spanworm (Lepidoptera: Geometridae).  Ann. Entomol. Soc. Am. 103(2): 135-145.

5Rajaei, H., M. Abaii, and A. Hausmann.  2010.  First record of the winter moth Operophtera brumata (Linnaeus, 1758) (Lepidoptera: Geometridae) in northern Iran.  Iranian Journal of Animal Biosystematics 6(2):63-68.  https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0ahUKEwjWgbGU3qnUAhUJxmMKHXHrA2IQFgg9MAQ&url=http%3A%2F%2Fijab.um.ac.ir%2Findex.php%2Fbiosys%2Farticle%2Fdownload%2F25213%2F4299&usg=AFQjCNGYV9wmYICCMDmP4ftvpf2sKx6plw&cad=rja

6Embree, D.G. 1970.  The diurnal and seasonal pattern of hatching winter moth eggs, Operophtera brumata (Geometridae: Lepidoptera). Can. Ent. 102(6): 759-768.  http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8557345

7San, N.V. and K. Spitzer.  1993.  Isolated populations of the winter moth, Operophtera brumata (Lepidoptera: Geometridae), their heavy metal content and parasitism.  Eur. J. Entomol. 90: 311-321.  http://www.eje.cz/pdfarticles/473/eje_090_3_311_VanSanSpit.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