UF/IFAS Okeechobee County Extension Service

458 Highway 98 North

Okeechobee, FL 34972-2578

Phone: (863) 763-6469

E- mail: indianco@ufl.edu 

October 25, 2011

Feature Article - for immediate release   

Dan Culbert - Extension Horticulture Agent

Get Savvy about Snails!

A recent news article was published in our local paper about a renewed infestation of Giant African Land Snails (GALS) in Miami.  While these critters are a real problem, as of October 20, the known finds of this recent infestation is limited to the Miami area.  

It is a good idea, as suggested, that if persons find this critter, that they should report it.  If you see one of these snails, call the FDACS DPI toll-free helpline 888-397-1517.

Our Extension office has had several calls and visitors ask for assistance with this issue since this story has run. Local residents have brought in several examples of suspected GALS, which have turned out to be another giant gastropod now known in our area for some time – the Channeled Apple Snail. 

So it’s an appropriate time to take a look at some of the commonly found snails found in this area and learn about their habits and management in and around our Florida Yards.  

Snail Habit 

Because we have some areas that are moist and rich in organic material, it is no wonder that a number of land-based (i.e. terrestrial) snails found in Florida.  Some terrestrial snails are native, while others have come from other areas.  Most of these snails are either beneficial or harmless. For example, Florida is host to some attractive but harmless tree-dwelling snails that feed on algae, fungi, and lichens, including at least one that is listed as threatened. However, a few snails may feed on economically important plants and have become pests.

 

Food sources

While some snails feed on dead or decaying organic material, there are some that feed on living plant tissue.  If the conditions of temperature humidity and the kind of organic materials are right, some snails can become landscape and garden.

 

Here’s an extreme example: the Giant African Land Snail (GALS) is a potential threat to more than 500 different kinds of plants, including vegetables, field, oil, ornamental and fruit crops.  Not only are the GALS agricultural pests, but they can also cause structural damage to buildings by consumption of plaster and stucco, and in large numbers can cause extensive damage.

 

A parasite in snails

In some, people bite back – quite literally -  as some snails are grown for human food.  Escargot is a dish of cooked snails, usually served with lots of garlic and butter as an appetizer in French cuisine. Several species of snails (e.g. Helix sp.) are grown for this purpose.

 

However, other snails can be a threat to public health because of their ability to spread diseases to animals and humans. They are known to be effective transmitters of a bacterium and a roundworm parasite, the rat lungworm.  Such diseases can be transferred to humans by eating raw, undercooked, infected snail meat and fluids, or even eating vegetables that have come in contact with infected snail slime.  Humans could also become infected by handling live GALS if their secretions come in contact with eyes, nose or mouth.  Bottom line: wear gloves to prevent infections if you need to handle the GALS snail.

Snail ID

GALS:  “Giant African Land Snail” is a common name used to describe several snail species that are native to Africa. They are among the largest land snails in the world, growing up to 8 inches long and 4.5 inches wide.  When fully grown, the shell has seven to nine complete spirals. The brownish shell may have stripes, and it covers at least half the length of the snail. Each snail can live as long as 9-10 years and survives both cool winters and warm summer temperatures. 

Because it contains both female and male reproductive organs, once fertilized it can produce tens of thousands of new snails.

 

Channeled Apple Snail

The channeled applesnail is the critter that has been a recent office visitor.  It occurs widely in South America and also now is found in Arizona and California. It is a serious pest of rice in Southeast Asia. The voracious channeled apple snail readily consumes most aquatic plants. It threatens natural lakes and wetlands because it competes with native apple snail species. Birds that depend on the native apple snail as its food source often can not eat this larger invader.

The shells of this invader vary from 1.5 - 3 inches in size. The color in the wild is yellowish to brown with or without dark spiral bands. They have 5 to 6 whorls that are separated by a deep, indented furrow, hence the name channeled.

Channeled Apple snails produce what looks like a glob of Pepto-Bismol colored goo that contains 200 to 600 loosely attached eggs.  They can be seen just above the waterline on docks, seawalls, trees, and plant stems. Compared to the eggs of native apple snails, those of the channeled apple snail are smaller, pinker, and more numerous. Eggs hatch in one to two weeks, releasing hundreds of juveniles into the water body.

Native Apple Snail

The native Florida apple snail is a favorite food of some native birds, the endangered Snail kite and the Limpkin.  With a length of 2 inches and a maximum diameter of 2½ inches, the Florida applesnail is distinguished from other applesnails by its pattern of dark brown bands on a lighter brown background. Its striped pattern also provides camouflage from predators.

For the most part, native applesnails feed upon soft plant material, preferring algae, grasses, and duckweed. However, in the absence of a preferred food source, they have been observed preying upon other snail eggs or even smaller snails.

Florida Tree snails

Many snails are found in trees, but only a few are exclusively arboreal for most or all of their life cycle. These tree snails are normally found on the ground only during egg-deposition or when dislodged from their perches. Some are up to 3 inches long, but tend to be smaller in colder areas. There are several different species with differences in stripes and color patterns. Several are endangered species and their range can be restricted to small areas.

One that is fairly common is the Lined tree snail; it has brown bands that point towards the tip of the whorled shell. This snail is found on twig tips of both native and exotic trees and shrubs in southern Florida and in the Caribbean. They typically measure about an inch in length.  

These true tree snails feed on epiphytic growths such as algae, fungi and lichens on trees.  They are not pests but can clear up the epiphytic “stuff” on tree limbs that some people find objectionable.

Cuban Land Snail

Deliberately introduced to the Miami area from Cuba in the early 1900s, the Cuban land snail is the most abundant of the large terrestrial snails in southern Florida.  It can be found as far north as Tampa, and is readily transported with potted plants, so it is a quarantine issue.

This snail has proved to be quite voracious, capable of consuming most plants it encounters. It attacks tropical fruit and citrus, most ornamental plants, and vegetable plants. On a site visit I made some time ago, these snails were so numerous  that they stripped the bark off mature oleanders; every step taken near the plant crushed hundreds of snails on the ground.

Adult Cuban lands snails are about an inch in size and possess 4–5 whorls.  They are brown or yellowish brown in color, sometimes with brown streaks radiating from the center.

Snail Management

Exclusion 

One of the best ways to prevent snail problems it to make sure they don’t arrive here in the first place.  Inspect any new plants carefully before bringing them home to reduce the chances of hitchhikers.  If you travel abroad, don’t bring extra guests with you, either on purpose or accidentally.   

And if you keep exotic pets, here’s another example:  A boy returning from Hawaii in 1966 brought three GAL snails into Florida, and his grandmother released them in her North Miami garden. In 1969, The Florida Division of Plant Industry was alerted to the infestations and began a survey and eradication program. By 1973, over 18,000 snails were destroyed. This is probably what has occurred again with the latest GALS infestation.  

Traps

The old beer in the saucer method can sometimes be used to capture and remove snails – apple cores or other materials may also be used to attract snails into a trap. The basic idea is to create an environment that is attractive, but once the mollusk enters, it cannot escape.

Predators

Here’s another alternative for controlling snails pests - the rosy wolf snail readily attacks other snails. It is native to the southeastern U.S., and is common in woodlands and gardens in Florida. I don’t know of any place that these could be purchased, but if you see them, know they are definitely good guys that should be left to roam your Florida Yard.

Cultural and Chemical management

If there are pesky snails in your garden or landscape, moisture management is the first step. Reduce the amount of water being used, and in some cases, removal of extra thick layers of leaf litter or mulch may be helpful in making the site less attractive to snails.

In some cases it may be appropriate to use some specific chemical pesticides for snails, but care is definitely in order with this management method.  Often the molluscides available for homeowner use are baits containing the active ingredient metaldehyde.  These can also be toxic to pets and wildlife.  Other products contain carbamate products or iron phosphate.  I have seen snail control products that may have a combination of these materials with other active ingredients such as insecticides. Will these other pesticides really be necessary for your situation? Read the label carefully and follow all instructions – the Label is the Law!  Please ask for our assistance if you need more information.

 

Additional information on exotic and native snails can be found in archived news articles on our website.  For more information, please contact the Okeechobee Extension office at 863-763-6469, or go to the Okeechobee Extension web page, http://okeechobee.ifas.ufl.edu.  Local residents can also stop by our office at 458 Hwy 98 North in Okeechobee.  Go Gators!

-30-

 

Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/ affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Millie Ferrer-Chancy, Interim Dean. Last update: 10/25/2011.  This page is maintained by Dan Culbert  

 References

Brown, Karen.  Pomacea canaliculata - Channeled Apple Snail. Gainesville: UF/IFAS Center for Invasive and Aquatic Plants, 2006. http://plants.ifas.ufl.edu/guide/pomcan.html

Brown Garden Snail,  Cantareus aspersus (= Helix aspersa).  Davis:  University of California, IPM Online, 2009.   http://www.ipm.ucdavis.edu/PMG/r107500111.html

Capinera, John L. and White, Jodi.  Terrestrial Snails Affecting Plants in Florida [EENY497].  Gainesville:  Florida Cooperative Extension Service, October, 2011. http://edis.ifas.ufl.edu/in893  Good reference on Florida pest snbails and what can be done about them.

Capinera, John L. Giant African Land Snail in Florida [ENY-512]. Gainesville:  Florida Cooperative Extension Service, October, 2011. http://edis.ifas.ufl.edu/in904  Specifics on the Giant African Land Snail.

Culbert, Dan.  “A new Slimy invader”. Okeechobee News, 9/5/05 and UF/IFAS Extension Service, http://okeechobee.ifas.ufl.edu/News%20columns/Apple.Snails.htm

Ibid. “Slow, Slimy, and Deadly”.   Okeechobee News, 5/24/04 and UF/IFAS Extension Service, http://okeechobee.ifas.ufl.edu/News%20columns/GALS.htm

Ibid.  “Snails in the Florida Yard”.  Vero Beach Press Journal, 8/2/2000 and UF/IFAS Extension Service, http://okeechobee.ifas.ufl.edu/082700%20Tree%20Snails.htm

DeGroat, Beth.  Pomacea paludosa - Florida Apple Snail.  Gainesville: UF/IFAS Center for Invasive and Aquatic Plants, 2006. http://plants.ifas.ufl.edu/guide/pompal.html

Deisler,  Jane E.  Tree Snails of Florida, Drymaeus, Orthalicus, Liguu sspp. (Gastropoda: Stylommatophora: Bulimulidae) [EENY148]. Gainesville: Florida Cooperative Extension Service, August 2011. http://edis.ifas.ufl.edu/in305  ID key to the small native snails found in many Florida Yards.

Giant African Land Snail.  Gainesville: FDACS/Division of Plant Industry, October 21, 2011 [access date].  http://www.freshfromflorida.com/pi/plantinsp/gals.html  This extensive webpage has reliable current information and numerous links about GALS, including some videos!

Giant African Snail Response Program. Gainesville: FDACS/Division of Plant Industry, September 28, 2011.   http://www.youtube.com/user/fdacsdpi#p/a/u/0/Wc8Dx2HcPgg ( 4:16 minute video, showing live GAL snails and where they were found in a Miami residential yard.)

Nordlie, Tom.  UF study: Invasive snail may damage diet of rare Everglades bird.  Gainesville: UF News, February 4, 2010. http://news.ufl.edu/2010/02/04/snail-kite/  How this snail threatens the native Snail kite bird.

Parasites – Angiostrongyliasis [Rat Lungworm]. Atlanta: Center for Disease Control, November 2, 2010 http://www.cdc.gov/parasites/angiostrongylus/gen_info/faqs.html This fact sheet describes the parasite that can be found in snails.

Sykes, Jr., P. W., J. A. Rodgers, Jr. and R. E. Bennetts. Snail Kite (Rostrhamus sociabilis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; 1995.  Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/171 Detailed identification key to Florida snails.

Thompson, Fred G.  An Identification Manual for the Freshwater Snails of Florida. Gainesville: Florida Museum of Natural History, March 5, 2004  http://www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm