Zapping curbs alien spinach.

Many Asians appreciate the taste of water spinach and its ability to fortify the diet with iron. Considered a nuisance plant in the United States, it's not legally available. Indeed, that's why many immigrants import this Ipomoea aquatica and plant it near their new homes. Lacking natural predators, it quickly begins covering lakes, streams, drainage ditches, and even soggy land, choking out native plants. In Florida, where illicit plantings have sprawled over areas spanning up to 50 acres, scientists have been scouting ways to limit the spread of this scourge.

Thai K. Van at the U.S. Department of Agriculture's Aquatic Weed Research Unit ill Fort Lauderdale, Fla., thinks radiation may be one solution.

Scientists suspect that individuals ,buy black-market water spinach to eat and men root scraps or me stems in water to produce new plants. Preliminary tests that Van has just conducted demonstrate that fresh samples lose their rooting ability once they receive a 500-Gray dose of radiation. This exposure, which leaves no radioactive residue, is half the amount permitted under federal law to curb spoilage in fresh produce.

If Van's finding is confirmed, the State of Florida may license commercial growers to raise the plant under quarantine--provided that all plants will be irradiated before they reach the market.