Invasive Snails Threaten Key Louisiana Crops
Apple snails eat the vegetation until there is no more; then, with a lung that enables them to breathe out of the water, they move onto dry ground to continue feeding.
About ten years ago, Pomacea maculata arrived in south Louisiana.
Now abundant in area swamps, marshes, and ponds, the giant apple snails are taking over. These non-native, invasive snails can grow to six inches in diameter, producing a big hunk of protein-rich meat. Escargot, anyone? Not so fast … as far as edibility goes, the parasitic rat lungworms hosted by the apple snail could cause serious health issues in humans if the snail is not cooked thoroughly, making even the bravest Cajun hesitate.
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The giant apple snail originates in South America...
... though mollusk experts disagree as to whether the snails arrived here via the aquarium trade or the bilges of ships coming from South America—possibly both, but the general consensus is that giant apple snails grow way too big for aquaria and prefer to eat the vegetation in the tank rather than clean the glass; hence, they were turned loose in ditches and waterways.
Its hunger for aquatic vegetation makes the giant apple snail a serious threat to other natural species vying for the same food.
Apple snails eat the vegetation until there is no more; then, with a lung that enables them to breathe out of the water, they move onto dry ground to continue feeding. Just how much damage could a snail really do, though? According to duck hunters in the Terrebonne and Atchafalaya basins and Acadiana crawfish farmers, plenty.
The disgruntled hunters claim that over three years, apple snails wiped out the aquatic vegetation within their duck lease—the same vegetation that lures migratory waterfowl to the ponds to feed. Apple snails move just as slowly as the smaller garden snail, but their spread was exacerbated by the floodwaters of 2016, which carried the snails from rivers into marshes and ponds. Here, they fight the crawfish for food. Making matters worse for crawfish farmers, the snails clog trap openings, preventing the mudbugs’ entrance. As recent as this past February, at least one crawfish farmer in Acadia Parish pulled his traps out of the water, because cleaning snails out of the traps was just too tedious and time consuming.
… as far as edibility goes, the parasitic rat lungworms hosted by the apple snail could cause serious health issues in humans if the snail is not cooked thoroughly …
Even though snails seem like a lowly creature, they get a leg up on the food chain because they are so prolific.
Females mature around three years of age and may live for eight years, during which time they can lay a clutch of up to two thousand eggs every ten days during the breeding season. Females slide out of the water onto hard surfaces like tree trunks, cypress knees, or other available plants to lay a clutch of bright pink eggs, the color of bubblegum. Scientists speculate that the pink color serves as a deterrent to predators, but it’s a hard theory to prove—the eggs are toxic and have no predators except for another non-native nuisance, Solenopsis geminata—a species of fire ant. The ants have been observed consuming the eggs with seemingly no ill effects. Maybe this is a case where one non-native invader will eradicate another, if only those fire ants could be rounded up with ease.
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Not only do these quickly-multiplying mollusks consume vast quantities of vegetation and lay millions of toxic eggs, they may soon pose a threat to agriculture in south Louisiana.
According to applesnails.net, apple snails will eat garden vegetables like lettuce, cucumbers, and green beans as well as garden weeds. Considering this troubling information, rice farmers are on the lookout for giant apple snails chowing down on their tender rice plants. Other than letting loose colonies of fire ants in the rice paddies, the only option is to remove the snails by hand, one by one.
Interestingly, Pomacea paludosa is a different species of apple snail native to Florida where birds like the snail kite and the limpkin enjoy a steady, controlling diet of them. Historically, the limpkins’ range stops in northern Florida, until this past December when several limpkins were discovered on Lake Boeuf in northern Lafourche Parish. Then in January, one lucky bird watcher spied two limpkins on the southern edge of Lake Houma right next to a very busy road.
In short order, birders from across the state, (and even from other states) lined the road in lawn chairs for a chance to see and photograph the limpkin pair. Jane Patterson, president of the Audubon Society Baton Rouge Chapter, observed the limpkins eating giant apple snails. Weeks of observation revealed that the limpkins had obviously found their home away from home, began nest building, and are now the proud parents of seven chicks.
Environmentalists, naturalists, and bird watchers are cheering for Mr. and Mrs. Limpkin and their little limpkins to stick around and diminish the local giant apple snail population. Actually, we’re all hoping they’ll send a message back home to Florida and invite all their relatives for dinner. Until Cajuns find a safe way to add giant apple snails to gumbo, there will be plenty of feed to go around.
If you would like to see more of the limpkins, please join the Louisiana Birds and Birdwatching Facebook group.
This article originally appeared in our May 2018 issue. Subscribe to our print magazine today.