Cesar Chavez and the grape boycott

When I was a kid, for years my mom steadfastly refused to buy grapes, because Cesar Chavez and the United Farm Workers were leading a grape boycott to protest the wages and working conditions of migrant farm workers.

So why just grapes? The conditions for migrant workers picking other crops must have been (and must still be) pretty darn awful.

According to this website,lettuce was also involved: