California Pest Rating Proposal
Cepaea nemoralis – Banded wood snail
Current Rating: Q
Proposed Rating: A
Initiating Event: Cepaea nemoralis is frequently intercepted by CDFA. A pest rating proposal is required to support its permanent pest rating.
History & Status:
Background: Cepaea nemoralis, known as the banded wood snail, is the most common species of land snail in Europe and has been introduced to North America. This snail is commonly found in urban areas, where it inhabits gardens and abandoned lots. They feed on dead and living plant material, carrion, fungi, moss, and insects1.
Cepaea nemoralis has a yellow, pink, or brown shell. The shell contains five dark bands. Banded wood snails are hermaphrodites, but cross fertilization occurs (each snail fertilizes the other). They often mate multiple times prior to egg-laying and can store sperm for up to 15 months. Eggs are buried in moist soil, hatching after about three weeks. The snails reach maturity in four years and may live as long as five to nine years 1, 4.
Worldwide Distribution: Banded wood snails are distributed throughout much of Europe, extending to Poland. This snail was introduced into North America during the nineteenth century, and it is currently found in Virginia, New York, Ontario, and Massachusetts1, 2.
Official Control: Banded wood snail is listed as a harmful organism in Canada, Israel, Japan, and Taiwan6.
California Distribution: Banded wood snails have never been found in the environment of California.
California Interceptions: Between January 2000 and August 2017, banded wood snails have been intercepted 20 times. These interceptions include border station inspections and high risk pest exclusion activities.
The risk Cepaea nemoralis (Banded wood snail) would pose to California is evaluated below.
Consequences of Introduction:
- Climate/Host Interaction: Banded wood snails can feed on a variety of live and dead plants and dead animals and insects, including remains of ants, beetles, spiders, mites, springtails, and aphids. Banded wood snails may establish in larger, but limited, warm agricultural and metropolitan areas of California. It receives a Medium (2) in this category.
Evaluate if the pest would have suitable hosts and climate to establish in California:
- 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: Banded wood snails are highly polyphagous and are known to feed on a wide variety of live and dead plants and animals. It receives a High (3) in this category.
Evaluate the host range of the pest.
- 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: Banded wood snails are obligately outcrossing hermaphrodites, with both individuals exchanging sperm during mating, and both individuals able to lay eggs afterward. On average, they lay 30-80 eggs that hatch in 15-20 days. Breeding takes place from April through October. The snail’s foot is used to create a cavity in the soil where the eggs are deposited1, 4. It receives a High (3) in this category.
Evaluate the natural and artificial dispersal potential of the pest.
- 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: The banded wood snail is not expected to lower crop yields. It could reduce the value of nursery stock by disfiguring plants with its presence and increase crop production costs in nurseries and orchards. The banded wood snail is a potential vector of Angiostrongylus vasorum, the French heartworm (a disease of wild and domestic canids) 3. It receives a High (3) in this category. Economic Impact: B, C, E: Environmental Score: 3
Evaluate the economic impact of the pest to California using the criteria below.
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 introduced, the banded wood snail is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. It might trigger new chemical treatments in orchards and nurseries and by residents who find infested plants unsightly. It is not expected to significantly impact cultural practices, home/urban gardening, or ornamental plantings. It receives a Medium (2) in this category.
Environmental Impact: A, D: Environmental Impact: Score: 2
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.
- 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 Cepaea nemoralis(Banded wood snails): High (13)
- Low = 5-8 points
- Medium = 9-12 points
- High = 13-15 points
Post Entry Distribution and Survey Information: The banded wood snail has never been found in the environment 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.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (13)
Uncertainty: Banded wood snails are commonly intercepted. There have been no formal surveys for this snail in the state. It is therefore possible that it could be present in some locations in California.
Conclusion and Rating Justification: Banded wood snail is not known to occur in California and might cause significant economic and environmental impacts if it were to become established here. Currently, an “A” rating is justified.
- Animal Diversity Web. Accessed September 7, 2017. http://animaldiversity.org/accounts/Cepaea_nemoralis/
2. Encyclopedia of Life. Accessed September 7, 2017.
3. G.A. Conboy. 2000. Canine Angiostrongylosis (French Heartworm). Accessed September 7, 2017.
4. Maggie Whitson. 2005. Journal of the Kentucky Academy of Science, 66(2):82-88. Accessed September 7, 2017.
5. Pest and Damage Record Database, California Department of Food and Agriculture, Plant Health and Pest Prevention Services.
6. USDA phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD). Accessed September 7, 2017.
Javaid Iqbal, California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6695; plant.health[@]cdfa.ca.gov.