Why are the joads called scabs in The Grapes of Wrath?

In "The Grapes of Wrath," the Joads are called "scabs" because they are viewed as individuals who undermine labor strikes by accepting work during a time when workers are protesting for better conditions and wages. This term reflects the tension between migrant workers seeking survival and the collective struggle of organized laborers. The Joads' desperate need for employment leads to their alienation from other workers, highlighting the broader themes of social injustice and class conflict in the novel.