Science: Grass Killer

Since Adam, agricultural thinkers have longed for a magic wand to make weeds disappear. The trouble is that weeds and crop plants are much alike; one farmer's weed may be another's crop. Any wholesale killer is apt to wipe out both together.

Both weeds and crops can be divided into two broad classes: grasses (wheat, corn, rice); and broad-leaved plants (cotton, vegetables, clovers). Scientists discovered several years ago that 2,4-dichlorophenoxyacetic acid (2,4-D) would kill broad-leaved plants while leaving grasses alone. But it is no help at all to gardeners, truck farmers and fruit growers whose broad-leaved crop plants are being choked with grass.

Last week, the U.S. Department of Agriculture announced something promising: a synthetic weed killer, isopropyl-N-phenyl carbamate (IPC), which does away with at least one kind of grass without hurting certain broad-leaved crops such as sugar beets and spinach.

British scientists found last year that IPC killed certain grain plants. U.S. scientists took the hint and tried the stuff on quackgrass, alias witchgrass, one of the peskiest weeds in the northern U.S. As little as 10 lbs. an acre, Agriculture reports, does the deed, killing even the nine-lived underground stems (stolons) which generations of farmers have grubbed from the soil by hand.