In the aphid's appetite for sweet corn, in the horn worm's hankering for tomatoes and the yen that sends the coddling moth to the apple, there is a living for Luther Gibbs.

As a gray and yellow Ag-Cat biplane roared past five feet off the ground, issuing a fine red mist, Gibbs, the down-to-earth president of the National Association of Aerial Applicators, explained his relationship with top pests in the agricultural world.

"We deposit the products that encourage them not to exist," he said.

Eleven pilots who used to be known as crop dusters but now style themselves as "aerial applicators" produced their own version of the punk movie "Liquid Sky" yesterday, dousing a strip of computer tape with gallons of dyed water at a fly-in clinic that is part of a program designed to improve spraying techniques.

Occasionally the wind wafted the nontoxic aerosol in the direction of the federal officials, chemical industry representatives and spectators gathered at the Beltsville Agricultural Research Center Airport to watch a clinic sponsored by Gibbs' association.

"They say it doesn't wash off," said a technician searching his white trousers.

To take them at their word, the pilots of the modern-day aerial spraying industry have outgrown the popular impression of the crop duster as a goggle-eyed daredevil in a long red scarf, swerving over barns and buzzing his mother-in-law.

Crop-dusting burgeoned after World War II as a seat-of-the-pants operation. Today the aerial distribution of pesticides, seeds, growth stimulants and ripening agents is an integral part of agribusiness in the United States. It demands planes that cost upward of $250,000, and expertise with toxic substances and new contraptions such as Through Valve Boom that have aerial applicators abuzz much as a new bird species excites ornithologists.

While many farmers in China still pick insects off their crops by hand, there are 3,300 aerial spraying companies in the United States--many of them one-pilot, one-plane outfits. They treat more than 180 million acres of farmland a year, predominantly in the southeastern section of the country.

"It's a different world than what it was," said Gibbs. "Everybody knows exactly what they are doing. They crop dusters of the 40s would be lost today."

It's not necessarily money that draws them to the work. Gibbs, who was seeding wheat last Saturday with his son, Luther Allen Gibbs, in Freemont, Ohio, has supplemented his income by hauling banners and dumping brochures and balloons on shopping centers. He said: "Today the average guy makes about $10,000 a year, but--they like the work."

The work is exciting because Section 137 of the Federal Aviation Administration regulations allows crop dusters to come as close to the ground as they want as long as they don't jeopardize people or property. The planes yesterday swooped in on pilot's verve at 100 miles an hour and swerved up instants later, banking and climbing steeply to avoid a stand of white pine at the far end of the runway.

The dangers posed by the profession consist chiefly of power lines, which caused 14 accidents last year, down from around 50 a decade ago. Many of the planes are equipped with sharp, wire-cutting bars on struts and windshields, and have a cable stretched between the cockpit and the tail to keep power lines from hooking the tail.

Crop duster Glenn Martin, of Frederick, tripped his helicopter on a power line once, crashed and watched the machine "beat itself to death."

Much of the focus at yesterday's clinic was on controlling the tendency of pesticides to drift on the wind, a concern that prompted the federal Environmental Protection Agency to put up $80,000 toward improving aerial spraying techniques.

"You get a lot of complaints," said Jack Neyland of the EPA's pesticides division. "There have been cases where an applicator's valves stuck open and he passed over a school. In Chicago, they were spraying for gypsy moths and some children got sprayed."

Says Nat Chandler, an agricultural liaison with the EPA, "Most of the trouble comes where suburban development runs into agricultural land. People have called in saying they're sick when planes were seeding rice."