Western Plant Diagnostic Network
First Detector News A Quarterly Pest Update for WPDN First Detectors Winter-Spring 2013 edition, volume 6, number 1
Dear First Detectors, The WPDN organized and hosted a In this Issue Malacology workshop from March 26 – 28, 2013, at the University of California, Davis, dealing with invasive snails and Page 1: Editor’s Note slugs. The workshop, given by the U.S. expert identifiers in the field: David Robinson (USDA-APHIS-Plant Protection and Quarantine) of the Academy of Natural Sciences in Pages 2 - 3: Brown Garden Snail Philadelphia, Patrick Marquez, Gregory Bartman, both with – The First Invasive Snail USDA-APHIS-PPQ in Los Angeles, and Rory McDonnell at UC Riverside. This workshop was requested by many state pest Pages 3 - 4: The Giant African identifiers because snails and slugs do not fit into plant Snail – “GAS” pathology or entomology, but rather are a totally different biological and generally unknown category. This edition describes several invasive and very damaging mollusks. Page 5: The Cuban Slug
Page 6: Theba pisana – the Mediterranean Snail
Pages 6 – 7: Xerolenta obvia – Being a First Detector entails knowing what the invasive Invasive snail in Montana species are, how to identify them, how to photograph and preserve them, and which agency to contact if found. Use Page 8: WPDN Pest Updates these online keys to help with the identification:
Contact us at the WPDN Regional Center at ID Guide to Terrestrial Gastropods and California Slugs P UC Davis: Phone: 530 754 2255 To submit a suspect gastropod sample, first completely Email: [email protected] Web: https://wpdn.org drown the snail or slug in water, and then preserve it in a P Editor: Richard W. Hoenisch container in ethyl alcohol or ethanol. See Preserving @Copyright Regents of the University of Gastropods California All Rights Reserved You can find the NPDN family of newsletter at:
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Photo by Dan and Hiromi Yoshimoto Photo by J. Patrick Fischer The First West Coast Invasive Snail
The Brown Garden Snail Cornu aspersum (Müller 1774)
The “Brown garden snail,” Cornu aspersum, is an edible snail widely and intentionally introduced worldwide. It is widely believed that the snail was introduced into San Francisco in the early days of the Gold Rush by a Frenchman wanting to enjoy escargot in the Wild West. Needless to say, the brown garden snail enjoyed the cool and moist west coast, and spread from the San Francisco Bay Area to coastal California, Oregon, and Washington. It is a pest of a wide range of agricultural and horticultural plants, especially citrus. In California alone, control/suppression programs currently cost $7 – 10 million a year. The brown garden snail has found its way into the southern Gulf states. There have been periodic outbreaks in New Jersey, Pennsylvania, and North Carolina. Although the garden snail is mainly nocturnal, it will emerge during the day after rain. It moves by means of a muscular foot; the mucus secreted by the foot aids with movement and leaves a tell-tale track behind. It feeds on a range of plant matter and can be serious pests. This snail has a strong homing instinct and spends the day, often in large groups, beneath stones and other structures. It hibernates through the winter in similar locations.
The garden snail is a hermaphrodite , meaning that it possesses both male and female reproductive organs; although it is able to self-fertilize, most snails mate with another snail. Reproduction takes place in early summer and begins with pairing and courtship. After a period in which the members of the pair caress each other with their tentacles, each snail pierces the skin of its partner with a calcareous "love dart," a spiny projection which is covered in mucus. The function of this love dart is unclear, but it is thought that the mucus may act to improve the survival of sperm. Mating then takes place; each snail inserts its penis into its partner at the same time. The snails separate, and the sperm is stored internally until the eggs are ripe. After the eggs have been fertilized, the snails dig pits in the soil in which to lay the eggs. They can lay from 40 to 80 eggs each. Hatchlings have translucent, delicate shells.
The garden snail is edible, and snail farming is currently a booming cottage industry. This species has also been used for centuries in traditional medicine, for example, broth made from the mucus was used to treat sore throats.
Brown garden snails mating Brown garden snails mating
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Brown garden snail eggs hatching A cluster of brown garden snail eggs The Giant African Snail (GAS) Lissasachatina fulica (Bowdich, 1822)
Photo: © R. Zimmerman, USDA-APHIS This beautifully marked snail, originally from coastal East Africa, has a voracious appetite and leaves behind disgusting slime in its path. GAS devastates agriculture, ecosystems, commerce, and human health. The snail can
carry a nematode causing deadly meningitis, the ratlung worm. It has been recognized as number 2 on the list of top 100 invasive species in the world, according to the Global Invasive Species Database . It is known to eat hundreds of different kinds of ornamental and food plant species. It has been spreading around the world, either intentionally (as Comparative size of the Giant African Snail! pets or food) or accidentally. See this Rat lungworm video. Snails are primarily nocturnal. During the day they are generally found under protective cover to maintain moisture. The Giant African snail can aestivate during the dry season and hibernate during winter at higher altitu des. This makes GAS very adaptable to a variety of climates and habitats. GAS as a snail is hermaphroditic. An adult fertilized GAS can lay enough eggs to produce a new colony. Eggs are laid within
8-20 days after copulation. Egg clutches can reach 500 or more eggs, which hatch within 1-17 days, depending on the temperature. Individual GAS can live for 4-5 years, and 9 years in captivity. They will literally eat most plant life. Because GAS grows so rapidly, it needs calcium to construct its shell. In Miami FL, where there is presently an infestation, GAS is eating the stucco off the exterior of houses to source calcium! GAS spread from eastern Africa into the Indian Ocean area, probably accidently. Before and during WWII, GAS was intentionally spread to numerous Pacific islands as a food source. It reached Hawaii in 1936, once again intentionally as a food source. GAS is on all the Hawaiian Islands. GAS was first introduced into the US in Florida by a young boy returning from Hawaii with 3 snails. He planned to raise them as pets. After a long campaign killing 18,000 snails, GAS was eradicated by 1972. GAS has spread throughout the Caribbean islands, after an intentional introduction in the Lesser Antilles. It soon spread throughout the entire Caribbean, causing extensive ecological and agricultural damage, as well as tourism. More often than not, however, the snails are smuggled illegally into the United States as pets or for food. They can be found at pet fairs, at swap meets, and purchased over the internet. GAS returned to FL in September, 2011, in the Miami-Dade area. The Florida Dept of Agriculture and the USDA established a Regulated Area and are in the process of eradicating the population. As of August, 2012, over 125,000
GAS from 545 properties in 21 cores (centers of infestation) have been detected and destroyed.
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In 2004, USDA inspectors discovered the importation of GAS by the pet store trade and educational institutions. Inspectors initiated a control program in April. By the time the program ended in late September, 6,700 snails were found in nine states and Puerto Rico. Wisconsin was the center of the infestation. One snail was found in both New Jersey and in Puerto Rico, and 3,139 were found in Ohio, where
GAS was used as an educational tool for school children. Fortunately, the snail did not establish itself in the natural environment. The GAS is an unwanted visitor to the United States. Although it has been traded at flea markets and kept as a pet, the U.S. Department of Agriculture has never issued a permit to import the
snails. All of the snails in the U.S. are here illegally. A local Wabash County, IN Health Department worker read that the snails would be available at a local flea market. The snails were confiscated and destroyed. As First Detectors, if you hear of GAS being offered for sale at pet stores, swap meets, or on-line, or know someone who may have them as pets, contact your state department of agriculture or the USDA APHIS at Report a Pest / Disease.
Photos © D. Robinson, USDA-APHIS-PPQ
Photo: © D. Robinson, USDA-APHIS-PPQ
GAS eggs
Mature GAS mating Mature GAS climb trees when too hot and/or crowded on the ground Giant African & General Snail Control
A board, flower-pot saucer, or unglazed flower pot placed in a shady location can serve as a suitable refuge for snails, where they can then be hand-collected and destroyed. The GAS seems to be particularly
attracted to banana and papaya fruit, so these can be used as baits to Photo by Lyle Buss, U of FL attract them. Newer mollusk baits contain iron phosphate as a toxicant. Iron phosphate is normally thought of as a fertilizer, but will also control snails and is the most environmentally-friendly product currently available. Iron phosphate baits are used in a variety of settings, such as
lawns, gardens and non-crop areas. Snail baits that contain toxicants are available at garden centers, but should be used in accordance with label instructions. Scatter the bait material among susceptible plants, as this will increase the probability that snails will find and eat the lethal bait.
Metaldehyde-containing baits have long been useful, and remain GAS eggs hatching available. Although effective, metaldehyde-containing formulations are quite toxic to pets and wildlife, so we discourage their use. Bait formulations containing boric acid also are available. Though not yet thoroughly proven, boric acid-containing baits seem promising for Giant African snail control. And, when handling GAS, wear rubber gloves to prevent rat lungworm disease. (from the University of Florida/IFAS WPDN News Extension)
Photos © D. Robinson USDA-APHIS-PPQ The Cuban Slug
Photo by T.Photos Beth © Kinsey D. Robinson, USDA-APHIS-PPQ Veronicella cubensis
Mature Cuban Slug from
Cuban Slugs on the Island of Rota Barbados Notice the variation in color and shape in these three photos. Cuban Slugs on eggplant in Hawaii
Cuban slugs (Veronicella cubensis) are common horticultural and agricultural pests and have become widely distributed in the Hawaiian Islands. Cuban Slugs are native to Cuba, but they have spread to other islands in the Caribbean and were accidentally introduced to the Hawaiian Islands. They were discovered on Oahu in 1981 and soon spread to the island of Hawaii. On the Big Island, Cuban slugs are especially common on the rainy windward side of the island where they can find a lush variety of plants to eat and the moist conditions they prefer. They actually out-compete other invasive slugs. In the 1990s, the Cuban slug arrived on Guam, probably on horticultural plants from Hawaii. Guam has little agricultural production so nothing was done to control its spread on the island. From Guam the Cuban slug was introduced to the agricultural island of Rota in the Northern Mariana Islands in 1996. Rota has rich soil and supplied most of the fruits and vegetables for Guam. The effect of the Cuban slug on Rota has been devastating. Almost all agricultural and horticultural plants have been destroyed. Fifty percent of the farms have been abandoned and all agricultural exports to Guam and elsewhere have ceased. The slug attacks a wide variety of garden and subsistence crops: banana, cabbage, breadfruit, cassava, various Citrus species, coffee, eggplant, hot and bell pepper, hibiscus, mango, lily, various melons and pumpkins, Mexican fire plant , okra, papaya, orchids, passionfruit, philodendron, soursop, starfruit, sweet potato, Polynesian arrowroot , taro, Thunbergia, angel trumpet flower, Vinca, and yam, as well as a number of medicinal plants important to the Rota culture. Tourism, once a valuable source of income, has collapsed due the complete infestation of the slug. The Cuban slug has since spread to American Samoa (2005) and Tahiti (2007).
A morning’s clean- Photos by M. Bonin up of Cuban slugs on the grounds of a hotel in Songsong , on the island of Rota. The larger garbage bag at the right weighs about 40 lbs. This is the reason tourism has dropped off on the
island.
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Theba pisana (Müller 1774) The Mediterranean snail
Photo by Tata Grasso Photo by X. Vasquez
Also known as the white garden snail, sand hill snail, white Italian snail, and Mediterranean coastal snail, this species is extremely invasive. Theba pisana usually lives in coastlands, in or near sandy habitats. In hot climates it aestivates often directly exposed to the sun, attached to grasses, shrubs or succulent plants, fence posts, tall weeds, and so on. It is common near beaches. In dunes it can live on nearly bare sand that is poorly fixed in place by grasses. In colder regions the snails do not aestivate, but they do climb on plants in dry weather. This snail does not survive serious winter frosts. It is native to the Mediterranean region (hence the name) and has been introduced into South Africa, southern Australia, and into California. This snail was first noticed in North America in La Jolla, San Diego County, California, in 1914. It is established only in San Diego County, but has been reported in both Los Angeles and Orange counties. An infestation in Los Angeles County in 1966 was declared eradicated in 1972. The snails were found and identified in August 1985, in San Diego, California, at several localities in about a 10 square mile area. T. pisana is also present in Bermuda, but has never been recorded from Florida. Why is the Mediterranean snail so dangerous? T. pisana is a significant pest of citrus, vines, legume crops and cereals in South Africa. In Australia, it feeds on a range of agricultural plants. As the weather becomes hotter and the ground is too warm for the snails, they climb up grain stalks and aestivate, so at harvest time, the snails are mixed in with the grain and ruin the crop. If T. pisana were to find its way into the US grain producing areas, there would be severe crop losses.
Photo courtesy of the Government of South Australia Photo by Fritz Geller-Grimm
Theba pisana on fennel Wheat in South Australia infested with
Theba pisana, thus contaminating the Michal Maňas harvest
Invasive snail found in Montana
Xerolenta obvia (Menke 1828)
The USDA's Animal & Plant Health Inspection Service (APHIS) confirmed on August 9, 2012, that snails collected about 20 miles southeast of Great Falls have been identified as eastern heath snails, Xerolenta obvia , a species native to eastern Europe that spreads by attaching to cargo containers or other conveyances used in international shipping. This snail species has the potential to reduce crop yield and quality, contaminate fruits, vegetables, and hay, and transmit plant and animal diseases.
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Eastern heath snails are similar in behavior to Theba pisana, the Mediterranean coastal snail described above. Heath snails lay eggs in the soil, infest a wide range of plant species including beans, peas, grapes and weeds, and can contaminate other crops such as grass hay and grain. The eastern heath snail is slightly smaller than a dime in diameter and is white with dark brown spiral bands. They feed on a wide range of plants including alfalfa, clover, lupine, wheat, barley, fruit trees, and weeds. This species is known for climbing on vegetation, fence posts, and other upright objects to escape high temperatures and will aggregate in enormous numbers in a behavior called massing. The snails were observed during this massing behavior about 15 miles southeast of Great Falls along State Highways 200, 331, and 89. Individual snails numbered in the hundreds of thousands and may actually represent a population in the millions. The snail prefers dry grassy areas and survives long periods of dry conditions by withdrawing into its shell and sealing the opening with a mucous membrane (article from KTVQ in Billings, MT). Also see the KRTV News Video on the Eastern heath snail for a sense of the biology and economic impact of this serious invasive. Photo by Ian Foley, MT Dept of Ag Photo courtesy of the MT Dept of Ag Photo by Ian Foley, MT Dept of Ag
Xerolenta obvia on grass stalks in Montana
Shipping Containers and other Culprits
Many invasive snails and slugs arrive attached to or in shipping containers. They can also be spread by trucks and trains. In the past, many European gastropod species came on shipments of tile and stone products. They could remain cool and protected among layers of such. The insect and gastropod identifiers with the USDA-APHIS-PPQ, the state departments of agriculture , and county extension offices are constantly inspecting, surveying, and identifying suspected invasives. The PPQ specialist and identifiers together with the state specialist protect US agriculture from invasive pests. The Cooperative Agricultural Pest Survey CAPS enables the program to target high-risk hosts and commodities, gather data about pests specific to a commodity, and establish better baseline data about pests recently introduced into the United States. And communication is essential. As First Detectors, get to know these excellent resources in your state.
Photo courtesy of the Port of Oakland
WPDN News
WPDN Pest Updates:
The Bagrada Bug, Bagrada hilaris, has spread from southern California and Arizona into New Mexico, Nevada, and Utah. It has been reported in Texas in 2012, but this has not been confirmed. This UC Riverside Pest Alert updates the biology, damage, and spread. In addition to the spread eastward, the Bagrada bug is moving up the coast of CA, now found as of October, 2012 in Ventura, Santa Barbara, and San Luis Obispo counties. Please see the UC Bagrada Bug update.
Brown Marmorated Stink Bug update and videos
OSU Extension Report on Spotted Wing Drosophila
Pest Tracker Pest Quizzes Test your ID skills!
Useful websites for invasives in the WPDN area are:
Western IPM Center, University of California IPM,
Pest Tracker, Hungry Pests, and
Field Guide to Target Insects in Pest Detection Programs
For the Pest Tracker site, select States and click on your state. This will give you the state and federal plant health officials and their contact information, plus news on pest
information and quarantines.
WPDN News