MOBILE, Ala. -- More than a year after the discovery of giant, voracious South American apple snails in Mobile's Langan Municipal Park, the gastropods have colonized most of Three Mile Creek, down to the Conception Street bridge

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The fact that the snails have migrated to within about a mile of the Mobile-Tensaw Delta represents a worst-case scenario, according to biologists.

Beginning Monday, state officials will administer a killing dose of poison to the two main ponds in Langan Park and most of Three Mile Creek. Authorities said they hope they're halting the advance of the snails before they colonize the Mobile-Tensaw Delta.

In addition to poisoning the thousands of fist-sized adult snails infesting the pond and creek, officials plan to smash every one of the bubble gum pink wads of snail eggs they can find, starting Saturday.

Those egg masses have become ubiquitous in the park, coating concrete walls, the face of the dam, the cattails, cypress knees and other plants emerging at the water's edge.

Volunteers, especially volunteers with kayaks, are more than welcome to come join the smashing party.

"These guys may be the perfect snail, and that makes them very hard to kill," said Ben Ricks, a biologist with the state Wildlife and Freshwater Fisheries division. "They have gills, they have lungs, they burrow. Every time we say, 'Well, why don't we do this to kill them,' it turns out that isn't going to work for one reason or another."

Egg smashers needed

To volunteer to smash snail eggs in Langan Park on Saturday, contact Tammy Herrington with Mobile Baykeeper at 433-4229.

Ricks and biologists from the U.S. Fish & Wildlife Service set 25 snail traps in the pond this week.

The biologists collected the traps Thursday morning, along with 50 pounds worth of baseball-sized snails. About a quarter of the snails in the traps were locked together -- shell opening to shell opening -- in the process of mating.

Researchers sample Langan Park snail invaders

Ricks said there is little hope that a single dose of the poison, copper sulfate, is going to do the trick. More likely, he said, the pond will have to be poisoned several times. If the poisoning causes a fish kill, the pond will be restocked.

Authorities plan to poison the creek all the way down to the Conception Street bridge. As it stands now, about all that is keeping the snails from expanding out of the creek is luck. It is possible, authorities said, they have already invaded the Delta.

"If the snail were to get into the delta, it could be devastating. This is an important, albeit icky, task that we are looking forward to doing on Saturday morning," said Casi Callaway, director of Mobile Baykeeper, which is coordinating the volunteers.

The snails have wreaked havoc in Louisiana, decimating rice crops and wetlands. They typically destroy all aquatic plants in the areas they infest, leaving behind an algae-filled wasteland.

It is believed they were dumped in the park after growing too large for a home aquarium.