slug | Pest Rating Proposals and Final Ratings

California Pest Rating for

Chinese Slug | Meghimatium bilineatum (Benson)

Gastropoda: Philomycidae

Pest Rating: A

PEST RATING PROFILE

Initiating Event:

Meghimatium bilineatum has been intercepted by CDFA’s high risk programs, border stations, and dog teams and presently has a temporary rating of “Q”. A pest rating proposal is required to assign a permanent pest rating.

History & Status:

Background: Meghimatium bilineatum is a terrestrial slug that lives in humid environments beneath plants and emerges to forage after rainfall¹. It is also found on cultivated land, landscaped urban areas, smooth-barked live trees, rocks, and under dead logs². Like other slugs Meghimatium bilineatum is presumably polyphagous on a wide variety of living and decaying plants. The slug may be transported long distances on nursery stock.

Worldwide Distribution: Meghimatium bilineatum is native to the mid and lower Yangtse basin of China¹. From there it has spread to Taiwan, Japan, Hawaii, Java, and Russia². Interceptions by CDFA on consignments from Florida and Ecuador indicate that it could be more widespread.

Official Control: Meghimatium bilineatum is not known to be under official control in any other states or nations³.

California Distribution: Meghimatium bilineatum has never been found in the environment of California.

California Interceptions: CDFA has intercepted Meghimatium bilineatum 16 times on nursery stock and ti leaves from Hawaii, Ecuador, and Florida.

The risk Meghimatium bilineatum would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Meghimatium bilineatum is a polyphagous terrestrial slug and is likely able to establish anywhere suitable moisture is available in California. It 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: Meghimatium bilineatum is presumably polyphagous on a wide variety of living and decaying plants. It 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: Females of Meghimatium bilineatum may live up to four years in the laboratory and produce an average of 932 eggs, indicating a high reproductive rate. The slugs may be transported long distances when infested nursery stock is moved. Meghimatium bilineatum 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: Meghimatium bilineatum does not appear to be documented as an agricultural pest and is therefore not expected to lower crop yields. However, slugs have the potential to significantly reduce the value of nursery stock by feeding on plants and contaminating them with their presence. The slugs are not expected to interfere with markets or change cultural practices. Meghimatium bilineatum has been documented as a vector of rat lungworm⁴. The slugs are not expected to injure animals or interfere with water supplies. Meghimatium bilineatum receives a Medium (2) 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: Meghimatium bilineatum is not expected to lower biodiversity, disrupt natural communities, or change ecosystem processes. It is not expected to directly affect threatened or endangered species or disrupt critical habitats. It may trigger additional treatment programs in the nursery industry and by residents who find infested plants or garden unacceptable. It is not expected to significantly impact cultural practices, home/urban gardening, or ornamental plantings. Meghimatium bilineatum 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 Meghimatium bilineatum: High (13)

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: Meghimatium bilineatum has never been found 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 (13)

Uncertainty:

There have not been any recent comprehensive slug surveys in California. It is possible that Meghimatium bilineatum could be present in some localities.

Conclusion and Rating Justification:

Meghimatium bilineatum has never been found in the environment of California and may have significant economic and environmental impacts if it were to establish here. An “A” rating is justified.