Posted on Sun, Jun. 22, 2008
Harmful snails invade S.C.
Island apple snails, originally from South America, could threaten health, environmentThe (Myrtle Beach) Sun News
MYRTLE BEACH — The gummy-looking, droplet-like clusters of pink eggs that clung to the bank of the pond appeared harmless enough, but S.C. nature officials are worried the snails that hatch from those eggs could pose a health risk and cause widespread ecological damage.
The island apple snails were found for the first time in the state in May in nearly a dozen ponds in the Laurel Woods subdivision and the Heron Point Golf Club off S.C. 707. Now officials are trying to eradicate them before they spread to the Waccamaw River, which would make containment efforts much harder. “Ideally, they would be exterminated,” said David Knott, a marine biologist with the S.C. Department of Natural Resources. “If it’s feasible, and we can do it without causing environmental damage, that’s what we’d like to do.”
The snail could eat just about all the plants in a pond and displace and even feed on native snail populations, Knott said. The snail also carries a parasite that could cause fatal meningitis and can transfer to people if it is handled without gloves, although Knott said he was unaware of a case in the United States.
The DNR has already dumped pesticide in the ponds in Heron Point and Laurel Woods, said Michael Hook, a field supervisor with DNR’s aquatic nuisance species program. The eggs in Laurel Woods have been slathered with vegetable oil to prevent them from hatching, Hook said.
“When we first saw them, it was like, ‘What the heck is this?’” said Linda Bogart, who lives in Laurel Woods. “Then the kids started coming up with these egg pods and handling them and breaking them apart. I have never seen anything like that. I was scared for the kids.”
In Laurel Woods, DNR found some aquarium gravel in one of the ponds, suggesting that someone dumped an aquarium with the snails — indigenous to South America — into the pond. From there, the snails, which can grow to the size of the palm of a hand, could have spread through culverts to other ponds, Hook said. They or the eggs could also have been carried by predators, such as birds or raccoons.
The island apple snail is one of several apple snail species and has been introduced in Texas, Florida and Georgia, a DNR news release said. Of even greater concern to biologists is another apple snail species, the channeled apple snail, which can devour rice and taro crops and is the 73rd worst invasive species in the world, according to the Global Invasive Species Database. That snail has been found in Arizona, California and Hawaii, DNR said.
The island apple snail cannot survive for long in water below 50 degrees, but it can burrow underground if the temperatures drop temporarily. South Carolina appears to be just warm enough for the snails, Knott said.
The apple snail was found nearly by accident. Tanya Meza, a resident in the Laurel Woods subdivision, said she called DNR to find out what fish she could get for a pond in the subdivision. When describing what already lived in the pond, she mentioned they had found some large snails. “I said, ‘Snails,’ and he’s like, ‘Wait a minute,’” Meza said. “All of a sudden, everything else didn’t matter.” Meza said she and her 9-year-old daughter, who first discovered the snail, were initially excited by the discovery but now are worried about the health and ecological effects.
DNR is spraying copper sulfate — a federally approved pesticide — in the infested ponds. The blue, granular substance will also kill algae but should not have any other detrimental effects, Hook said. Hook said he sprays about 10 feet from the edge of the pond, where most of the snails live. DNR plans to treat the infested ponds once a month throughout the summer if new eggs are found. The copper sulfate costs $2.50 a pound. Hook said DNR initially estimated spending about $1,000 on the snails.
A challenge, he said, is getting a small boat to the larger ponds for treatment. After some searching on a rainy afternoon Thursday, Hook found a dirt road surrounded by trees that led to a 2-acre pond near Heron Point. It was just wide enough for the boat to get through. “I see some eggs!” Hook said as he walked to the edge of the pond. “That didn’t take long.” The copper sulfate was poured into a funnel-shaped, electric applicator attached to the side of the boat. Once in the water, a blue spray spread around the pond as the boat went from one end of the pond to another.
Nancy Cave, the north coast office director for the Coastal Conservation League, an environmental group, said invasive species such as the apple snail can threaten local ecosystems. She supported DNR’s removal efforts. “People need to be really careful and really think about what they’re doing when they take an action like dumping an aquarium, or planting a plant that they don’t know anything about,” Cave said.