The regional Immigration and Naturalization Service commissioner said in Fresno that the amnesty registration program for alien farm workers is succeeding. But a local Farm Bureau official predicted disaster for the 1989 harvest season. Harold W. Ezell, INS regional commissioner from Los Angeles, said the agency's Special Agricultural Worker program has reached 60,000 alien farm workers in California with information about the registration program required under the new immigration law. The law grants amnesty to thousands of illegals who have lived in this country since before Jan. 1, 1982. But Don Laub, president of the Fresno County Farm Bureau, said the program will be unable to supply the estimated 170,000 workers needed at the peak of the California harvest season. After December, 1988, farmers who hire illegal aliens will be subject to prosecution.