A species of snail that is considered one of the worst agricultural pests in California has been discovered in Pennsylvania, posing a potentially expensive threat to the state's farms and nurseries.

"The last thing Pennsylvania wants is this snail rampaging across the countryside," said David Robinson, a snail specialist for the U.S. Department of Agriculture. "It's a major pest. It's one of the worst snail problems there is. It feeds on practically anything green and growing."The brown garden snails were discovered last month in the garden of a Philadelphia schoolteacher, who told officials that they had been in her garden for 10 years.