MOBILE, Ala. (AP) — Alabama officials concerned about the rapid migration of giant South American snails are about to try to halt their advance in Mobile County.

Ben Ricks, a biologist with the state Wildlife and Freshwater Fisheries division, says a heavy dose of poison will be administered on Monday two ponds in Mobile’s Langan Park and in most of Three Mile Creek.

Authorities said they want to stop the advance of the apple snails before they colonize the Mobile-Tensaw Delta.

In addition to poisoning the thousands of fist-sized adult snails, officials say they plan to smash every one of the pink wads of snail eggs they can find, beginning Saturday.

Experts say the snails typically destroy all aquatic plants in areas they infest, leaving behind an algae-filled wasteland.