As if fire ants and kudzu weren't bad enough, now we have a new pest.

One biologist compares the persistent green weed to ''The Blob,'' the title character in the 1950s sci-fi classic flick that grows and grows and consumes everything in its path. Other scientists describe the plant as looking like little heads of lettuce or squished green grapes. Then they use terms like noxious, invasive and just plain scary. Even the species name sounds sinister: salvinia molesta.

No one has anything good to say about what's more commonly known as giant salvinia, a Brazilian tropical floating fern that's found a home in slow-moving streams and freshwater ponds and lakes from the Carolinas to California, and even in Hawaii.

A federal survey shows infestations in several states with mild winters, including Georgia, Alabama, Mississippi, Louisiana and Florida, plus along the lower Colorado River on the California-Arizona state line.

The plant can double in size in eight to 10 days, and grow into feet-thick mats of floating vegetation, blotting out all light beneath it and effectively killing anything trying to live there. It also can clog irrigation and electric generation intakes.

Each leaf is about the size of a quarter, and the plant trails a long brown root that looks like silk from an ear of corn.

(The New York Times.)