West Indians. traditionally used in the groves at harvest time. are welltrained professionals. Their earnings are an important dollar source for the countries that supply them. Mr. Wirtz envisions a minimumwage law covering farmworkersa proposal that south Dade growers say would ruin themand a nationwide chain of trailer parks to house workers as they follow the harvest season. Once farm labor is organized to bargain for itself. he declares. other benefits will accrue. The plight of the domestic migrant laborer has indeed been pitiful and pressure to do something about this has been growing. A great deal in fact has been done. Mr.