The nature of nature has changed the nature of pesticides. Experts now count pesticides as having only limited lifetimes of usefulness before nature adapts and disables them.

In the battle to keep crop plants pristine, nature is moving faster than man. The number of plant, insect and animal pests resistant to chemical pesticides is growing rapidly while the number of new pesticides has declined. Researchers have found more than 447 insects that have become resistant to pesticides, along with seven animals -- including rats -- that have toughened up against chemicals.

There are no longer effective pesticides to control the Colorado potato beetle on Long Island, the tobacco budworm and the diamondback moth. Hungary is the major maize-growing region for Eastern bloc countries, but 75 percent of its land is infested with herbicide-resistant pigweed.

As a result, a new National Research Council report says, "We see little justification in maintaining the polite fiction that pesticide resistance is solely a technical problem that can be readily overcome with the right new pesticide . . . . "

The usual strategy of simply changing pesticides no longer works, according to the report prepared by the Board of Agriculture of the council, an arm of the National Academy of Sciences.

Not only are fewer chemical compounds available as pesticides, but firms are reluctant to invest the large sums necessary in products that may soon be overcome by nature's resilience.

The report suggests that new tactics are necessary, including using biotechnology to provide information at the molecular level that may allow researchers to find new "targets" to attack in the pests' systems, varying dosages and combinations of pesticides and using more nonchemical methods, such as disturbing pest habitats or protecting pests' natural enemies.

Nature, of course, will continue to adapt and resist.