A U.S. Department of Agriculture official told doubting California growers that Mexican avocados will only be allowed into this country if it is scientifically proved that they do not pose a risk to the state's avocado groves.

He was fending off claims made during a tumultuous two-day public hearing in Escondido by California growers, who produce 90 percent of the nation's avocados, that the USDA's Animal and Plant Health Inspection Service has already made up its mind to partially lift the 81-year-old ban.In July, Aphis published a proposed rule change that would allow avocados

from designated groves in Michoacan, Mexico, to be imported into 19 states in the Northeast from November to February. The plan calls for strict measures covering the harvesting, packing and shipping of the avocados.

Aphis scientists called these measures a "systems approach" because their cumulative impact would prevent pest infestation. Michoacan avocado groves are said to harbor nine pests, some of which are so deadly that the only way to destroy them is to cut down infected trees and burn them.

After listening to numerous speakers bash the plan and charge that it would be ineffective and unenforceable, Michael Lidsky, the Aphis hearing officer in charge of the two-day program, assured the growers that Aphis has not come to any conclusions. "Our job is to get your comments and consider them. No decisions have been made," he said.

Grower after grower accused the Aphis panel, composed primarily of scientists, of bowing to political pressure from U.S. trade officials. They said the U.S. government intends to lift the 81-year-old ban to demonstrate its commitment to the North American Free Trade Agreement.

"I am proud to be an American, but I am ashamed to be up here today," said Larry Rose, president of the California Avocado Society. "I am embarrassed that you professionals have sacrificed your integrity for this political facade," he said.

In an interview, Mr. Lidsky said Aphis is charged with considering only the scientific issues involved in the potential lifting of the ban, and its scientists will not consider trade or political implications.

More than 50 growers, scientists, statisticians and government officials spoke at the hearing. Mexican as well as California growers turned to the best scientists they could find to prove their case.

Enrique Batista, chairman of the Michoacan Avocado Commission, said eminent scientists from the United States, Mexico and Brazil have examined the designated groves and production facilities and declared them to be safe for exporting their avocados to the United States. He noted that U.S.-owned companies have avocado processing plants in Michoacan.

Aldo Malavasi, a Brazilian geneticist who serves as chairman of a working group of scientists attempting to eradicate fruit flies in the Western Hemisphere, said the type of systems approach outlined in the Aphis plan is commonly accepted today in the scientific community as a way to combat pest infestation.

Scientists who spoke on behalf of the California growers, however, said the methodology and risk analysis used in the Aphis report are seriously flawed. Jan Nyrop, an entomologist at Cornell University in Ithaca, N.Y., said he took the same data used by Aphis scientists and reached an entirely different conclusion.

"If in science you get two contradictory results from the same experiment, you don't accept it," he said.

California growers stressed what they called the real world issues surrounding the importation of Mexican avocados that harbor pests. Gil Henry, president of Henry Avocado Co., noted that packing houses routinely buy, repack and transship fruit they can sell for a higher price than they paid.

In the case of Mexican avocados, he said, packing houses in the 19-state importation area can re-sell the cheaper Mexican avocados in California at a profit of $9,000 to $10,000 a truckload. "They have a strong incentive to transship," he said.

Most speakers stressed Mexico's the pest problems. Leo McGuire, an entomologist on the San Diego County fruit fly task force, said thousands of fruit flies were trapped by U.S. scientists working in Michoacan over a four- month period.

"How is it that we find one fruit fly in California and it's a crisis, but Mexico has thousands of fruit flies and they have no problem?" he asked.

California growers said they do not fear competition from Mexican avocados. They said thousands of pounds of fresh avocados are imported each year from Chile, which is pest free. Also, processed avocados are routinely imported

from Mexico.