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This very small slug (25-35 mm) is a yellowish- dark brown slug that can also range to almost black in coloration. It has tentacles that have a smoky, bluish black color and the surface of the slug is a furrowed texture. Deroceras leave is a keeled slug that has a breathing pore (pneumostome) present just at the end of the keel.
Despite its small stature, these slugs can damage and kill seedlings. Deroceras leave will feed on seeds, roots stems and leaves of many plant and crop species. In several Pacific Islands and New Zealand, this species has been found to carry the nematode Angiostrongylus cantonensis. In its native European range, it is known to carry several other nematode species from different genera including Angiostrongylus¸ Elaphostrongylus, Filaroides, Parelaphostrongylus, Trilobostrongylus.
Thankfully, in the continental United States, this species has not been found to naturally carry Angiostrongylus cantonensis but experimental infections from New Orleans have shown it to be a successful host.
**If you ever see these specimens, please do not pick them up with your bare hands. Use gloves or disposable forceps**
Deroceras laeve has multiple lifecycles per year, up to 5 generations in one year! These slugs reproduce by self-fertilization so all animals have the potential to reproduce. Eggs are between 1-3mm in diameter and can hatch within 10-15 days. The cream-colored eggs are usually laid in leaf litter and soil crevices. In order for this species to be successful, they always need to be near bodies of water.
This slug has been present in the United States that it was thought this species was native to the United States, until molecular work showed they were from Europe. Not much else is known about their introduction but it is speculated that they were brought over by European colonists in the 1700s.
Europe
U.S. Present: AL, AK, CA, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MD, ME, MI, MS, MO, NC, ND, NE, NJ, NM, NY, OH, OK, PA, SD, TN, TX, UT, VA, VT, WA, WI, and WV.
U.S. Habitat: Deroceras laeve, like many slugs, are omnivorous and can find food wherever and moist environment is present like a marshes, wetlands, woods and greenhouses. It has been found to feed on living and dead plants, feces, carrion, and living animals such as earthworms and aphids, and is a known horticultural and agricultural pest. It is a Palearctic species and can tolerate various elevations, making many of the United States viable habitat for this invasive species.
It does resemble other Deroceras species but those can be differentiated by genitalia structure or molecular analyses.
Please remove any of these pests from your yard but use gloves when handling them! Also, be sure to wash your hands off with hot water and soap afterwards. This soft-bodied slug could be susceptible to diatomaceous earth, salt, or slug repellent. Diatomaceous earth is very effective plant-friendly management strategy that dries out slugs and snails. It can be bought at any gardening and home improvement store. For a non-toxic solution you can submerge them in soapy water overnight (in a full, water-tight container) and dispose of them the next day. Shallow traps baited with beer or apple cider have shown to be effective, and the slugs can be disposed of in the morning.
Commercially produced metaldehyde slug traps can be set up to reduce slug populations; but slug bait is very toxic to domestic animals. If you have domestic animals you can use organic slug bait which is iron-phosphate based and NOT-metaldehyde based. Even with the organic slug bait, do not make it easily or consistently accessible to domestic animals.
We are actively tracking the distribution of this invasive pest. To report a potential sighting, please email a photo of the slug and provide your location information to Ashley Morgan-Olvera, M.Sc. (arm001@shsu.edu).
If you try to physically remove the slugs on your own, be sure to wear gloves during physical removal of these slugs in case they are infected with Angiostrongylus cantonensis. Also, be sure to wash your hands off with hot water and soap afterwards.
References
Alicata, J. E. 1950. Observations on the biology and control of a garden slug injurious to orchids in Hawaii. Pacific Orchid Society, Hawaii 8:279–285
Alicata, J. E., & McCarthy, D. D. (1964). On the incidence and distribution of the rat lungworm Angiostrongylus cantonensis in the Cook Islands, with observations made in New Zealand and Western Samoa. Canadian Journal of Zoology, 42(4), 605-611.
Barker, G. M. 1999. Naturalised Terrestrial Stylommatophora (Mollusca: Gastropoda). Fauna of New Zealand, Number 38. Manaaki Whenua Press, Canterbury, New Zealand. 254pp.
Campbell, B. G., & Little, M. D. (1988). The finding of Angiostrongylus cantonensis in rats in New Orleans. The American journal of tropical medicine and hygiene, 38(3), 568-573.
McDonnell, R. J., T. D. Paine, and M. J. Gormally (2009) Slugs: A guide to the invasive and native fauna of California. University of California Division of Agriculture and Natural Resources Publication # 8336.
Internet References
https://extension.psu.edu/slugs-as-pests-of-field-crops
http://edis.ifas.ufl.edu/in891
http://idtools.org/id/mollusc/factsheet.php?name=Deroceras%20laeve
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